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PSEB Class 10 Biology Chapter 7 Control And Coordination Question and Answers

Control And Coordination Questions

Question 1. What is the difference between reflex action and walking?
Answer:

Animals Nervous System Difference Between Reflex Action And Walking

Question 2. What happens at the synapse between two neurons?
Answer:

The synapse between two neurons is a junctional complex that permits an axon end of a neuron to pass its electrical or chemical signal to the dendrite end of another neuron.

  • There is a fluid-filled narrow space between the two neurons. It is called synaptic cleft. The presynaptic axon end of the neuron is bulb-like.
  • It contains many synaptic vesicles having neurotransmitter chemicals. The postsynaptic dendrite end of the next neuron has a trough-like depression. Its membrane has receptors for the neurotransmitter.
  • As the impulse reaches the presynaptic bulb, the synaptic vesicles move to the cleft side and burst open.
  • The released neurotransmitter sensitizes the receptors that in turn create the electrical impulse.
  • Synapse allows a unidirectional flow of information from the axon end of one neuron to the dendrite end of the next neuron.

Read And Learn More PSEB Class 10 Biology

PSEB Class 10 Biology Chapter 7 Control And Coordination

Question 3. Which part of the brain maintains posture and equilibrium of the body?
Answer: Cerebellum.

Question 4. How do we detect the smell of an agarbatti (incense stick)?
Answer: Burning of agarbatti releases numerous molecules of incense. They enter the nose and come in contact with particular sensory hair of olfactory cells.

An impulse is generated. It passes into the olfactory bulb which relays it to the temporal lobes of the cerebrum for interpretation.

Question 5. What is the role of the brain in reflex action?
Answer: Like the spinal cord, the brain can also play a direct role in certain reflex actions called cerebral reflexes, for example., closing of eyes or flashing of light.

In such cases, brain acts as a relay station in which the impulse of sensory neurons is transferred to motor neurons through an interneuron.

Question 6. What is reflex action? Explain the mechanism of reflex action with a suitable example.
Answer:

Reflex action is a nerve-mediated automatic and spontaneous response to a certain stimulus without consulting the will of the individual.

  • The stimulus for reflex action is picked up by its receptor. The receptor is connected to a sensory neuron. An impulse generated in it is passed to the central nervous system.
  • The central nervous system acts as a relay or modulator. With the help of an interneuron, it transfers the impulse to a motor neuron. The motor neuron takes the impulse to the effector organ for response.

Question 7. Name the three major regions of the brain. Which part of the brain maintains posture and equilibrium of the body?
Answer:

Three regions of the brain. Fore brain, midbrain, and hindbrain. Maintenance of posture and equilibrium. Cerebellum.

Question 8.

  1. Distinguish between voluntary and involuntary actions of our body.
  2. Choose involuntary actions among the following: reading, beating of heart, salivation in mouth on viewing tasty food, talking.

Answer:

  1. Voluntary action is under the control of the will and is performed with the help of striated muscles. Involuntary action is performed without instructions from will with the help of smooth muscles.
  2. The beating of the heart and salivation in the mouth on viewing a tasty food are involuntary actions.

Question 9.

  1. Name two main regions of our central nervous system,
  2. Which one of them plays a major role in sending commands to muscles to act without Involving the thinking process,
  3. Name the phenomenon involved.

Answer:

PSEB Class 10 Biology Chapter 7 Question And Answers

  1. Brain and spinal cord.
  2. The spinal cord has a major role in sending instructions to muscles without involving the thinking process.
  3. Reflex action.

Question 10. Write the function of the following :

  1. Sensory neuron
  2. Cranium
  3. Vertebral column
  4. Motor neuron.

Answer:

  1. Sensory Neuron. Conveying impulse or sensation from receptor to central nervous system.
  2. Cranium. Covering and protection of the brain.
  3. Vertebral Column. Covering and protection of the spinal cord.
  4. Motor Neuron. Conveying impulse for action from the central nervous system to the effector organ.

Question 11. Identify the part of a neuron

  1. Where information is acquired
  2. Through which information travels
  3. Where the impulse must be converted into a chemical signal?

Answer:

  1. Dendrite
  2. Axon
  3. Synapse.

Question 12.

  1. What is a reflex arc?
  2. Why have reflex arcs evolved in animals?

Answer:

  1. A reflex arc is nerve nerve-based pathway performed by an impulse from the receptor of stimulus to the effector organ through the central nervous system without consulting the will of the individual.
  2. Reflex arcs evolved in animals even before the evolution of intelligence as a survival mechanism because they can provide immediate responses to harmful stimuli.

Question 13. Stale the sequence of events through a reflex arc which occurs when a bright light is focussed on your eyes.
Answer:

  • Bright light is sensed by receptors present over the eyes. The sensation is picked up by sensory neurons and taken to the superior quadrigeminal.
  • Intemeurons present in the superior corpora quadrigemina transfer the impulse to motor neurons. The motor neurons close the eyelids as well as narrow the pupil.

Question 14.

  1. Name one gustatory receptor and one olfactory receptor present in human beings.
  2. Write a and b in the given flow chart of neurons through which information travels as an impulse.

Dendrite a → b → End point of a neuron.

Answer:

  1. Gustatory Receptor. Taste buds over the tongue.
    1. Olfactory Receptor. Olfactory epithelium in nasal chambers.
  2. Dendrite → Cell body → Axon → End point of a neuron.

Question 15. What is a nerve impulse? State the direction followed by a nerve impulse while traveling in the body of an organism.
Answer:

A nerve impulse is a progressive electrical wave or signal that develops in response to a stimulus and travels along a nerve fiber to reach another nerve, muscle, or gland.

Direction Of Nerve Impulse

Dendrite → cell body → Axon → Axon end → Dendrite/gland/muscle.

Control And Coordination PSEB Class 10 Notes

Question 16. List in tabular form two differences between reflex action and walking.
Answer:

Animals Nervous System Difference Between Reflex Action And Walking.

Question 17. Which part of the nervous system controls reflex arcs? Trace the sequence of events that occur when we touch a hot object. Mention the part of the neuron that requires information and the form in which information travels.
Answer:

Reflex arcs are controlled by the central nervous system (many in the spinal cord) without analyzing them. CNS functions as a coordinator or relay station for transferring sensory information to motor information.

Events. A hot object is the stimulus. As it is touched, the stimulus is picked up by skin-based receptors. From receptors, the information is taken up as an impulse by sensory neurons.

  • Sensory neurons take the impulse to the spinal cord. In the spinal cord, the impulse is transferred to motor neurons through interneurons.
  • The motor neurons take the impulse to the muscles of the hand which pull away the arm. Information travels in neurons in the form of electrochemical impulses.

Question 18. What is the structural and functional unit of the nervous system? Name any two components. Which structure in a neuron helps to conduct a nerve impulse

  1. Towards the cell body
  2. Away from the cell body.

Answer:

Structural and Functional Unit. Neuron.

Components of a Neuron. Dendrites, cell body, and axon.

  1. Dendrite
  2. Axon

Question 19.

  1. Which part of the brain controls Involuntary actions?
  2. Write the function of any two regions of It.

Answer:

Hind brain is a part of the brain that controls involuntary functions. It has three parts—pons, cerebellum, and medulla oblongata.

  1. Medulla Oblongata. It regulates blood pressure, heart rate, and breathing. Several reflex actions have centers in the medulla oblongata, viz., swallowing, vomiting, sneezing, coughing, salivation, and peristalsis.
  2. Cerebellum. It involuntarily co-ordinates muscular activities of the body. The cerebellum maintains equilibrium during different activities or postures of the body.

Question 20.

  1. If the cerebellum is not functioning properly, state the activities of our body that are affected.
  2. How do muscle cells move?

Answer:

PSEB Class 10 Biology Important Questions

  1. Impairment of the cerebellum shall result in non-coordination of body activities and defects in maintaining balance or posture of the body.
  2. Muscle cells move in response to excitation provided by a neuromuscular junction. The motor impulse passes to the bulb end of the motor end plate of an axon.
    • The bulb is in near contact with the sole plate of the muscle cell. As the nerve impulse reaches the bulb, it activates the synaptic vesicles.
    • The vesicles move to the membrane and burst open to release molecules of neurotransmitters.
    • They activate receptors over the end plate and cause activation of muscle interior releasing calcium and causing contraction of muscle cells.

Question 21. Name the part of the brain that controls

  1. Voluntary actions
  2. Involuntary actions.

How is the brain protected from injury and shock?

Answer:

  1. Voluntary Actions. Cerebrum.
  2. Involuntary Actions. Hindbrain.

Protection of the Brain.

  1. Covering of brain by cranium,
  2. Holding of the brain by meninges,
  3. Presence of shock-resistant fluid medium both inside and outside the brain.

Question 22.

  1. Name the system which facilitates communication between the central nervous system and other parts of the body.
  2. Mention two types of nerves it consists of along with their organs of origin.

Answer:

  1. Peripheral Nervous System (PNS) facilitates communication between the central nervous system (CNS) and other parts of the body.
  2. The peripheral nervous system consists of two types of nerves
    1. Cranial from the brain, 12 pairs
    2. Spinal from spinal cord, 31 pairs.

Question 23. Trace the sequence of events that occur when a bright light is focused on your eyes.
Answer:

It is an example of a cerebral reflex.

Receptor cells of eyes → Sensory neurons → CNS (Brain) → Motor neurons → Eye muscles → Pupil contracts and eyelids close.

Question 24. List in tabular form three distinguishing features between the cerebrum and cerebellum.
Answer:

Animals Nervous System Distinguishing Features Between Cerebrum And Cerebellum

Question 25.

  1. Name a part of the human brain that controls
    1. Voluntary actions and
    2. Involuntary actions.
  2. Write the function of the peripheral nervous system. Name the components of this system stating their origin.

Answer:

PSEB Class 10 Science Chapter 7 Solutions

  1. Voluntary actions. Forebrain/cerebrum.
    1. Involuntary Actions. Hind brain/medulla oblongata.
  2. Peripheral Nervous System (PNS) connects different parts of the body with the central nervous system. It consists of nerves. Depending upon their origin, nerves arc of two types, cranial (from the brain) and spinal (from the spinal cord).

Question 26. Name parts in the diagram. What is the term given to the sequence of events occurring in the diagram?

Animals Nervous System Reflex Arc.

Answer:

  1. —Receptor (skin)
  2. —Sensory neuron
  3. —Spinal cord
  4. —Relay neuron
  5. —Motor neuron.

Term. Reflex arc.

Question 27. A cheetah on seeing a prey, moves towards it at a very high speed. What causes the movement of his muscles? How does the chemistry of cellular components of muscles change during the event?
Answer:

  • The sight of prey generates a nerve impulse that reaches the muscles. A neurotransmitter is released. It causes the activation of muscles through the release of calcium.
  • Calcium brings about a shortening of muscles through the sliding of myosin fibrils over actin fibrils. Shortening and relaxing of muscles allow the cheetah to move at high speed.

PSEB Class 10 Biology Chapter 9 Heredity Question And Answers

Heredity Short Question And Answers

In each question, two statements are given- one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below :

  • Both assertion and reason are true and reason is a correct explanation of the assertion.
  • Both assertion and reason are true but reason is not the correct explanation of the assertion.
  • Assertion is true but reason is false.
  • The assertion is false but the reason is true.

Question 1. Assertion (A). The sex of a child in human beings will be determined by the type of chromosome he or she inherits from the father.

Reason (R). A child who inherits an ‘X’ chromosome from his father would be a girl (XX) while a child who inherits a ‘Y’ chromosome from the father would be a boy (XY).
Answer:  (1)

The sex of the children is determined by what they inherit from their father and not the mother. Justify.
Answer:

Women are homogametic. They produce one type of ova 22 + X. Men are heterogametic. They have two types of sperms, androsperms (22 + Y) and gynosperms (22 + X). During fertilization, it is the sperm type which determines the sex of the child—male (22 + X and 22 + Y or 44 + XY) or female (22 + X and 22 + X or 44 +XX).

Read And Learn More PSEB Class 10 Biology

Question 2. State the importance of chromosomal differences between sperms and eggs of humans.
Answer:

The chromosomal difference between sperm and eggs of humans is basic to the determination of the sex of the child. Eggs are of one type carrying the genetic complement of 22 + X. Sperms are of two types, androsperms with 22 + Y chromosomes and gynosperms with 22 + X chromosomes. The two types of sperm determine the sex of the child. Justify.

Question 3. Name the organism Mendel used for his experiments. Explain F1 and F2 progeny obtained by Mendel when he bred tall and short varieties of the organisms he experimented with.
Answer:

The experimental organism used by Mendel was the Garden Pea (Pisum sativum). Mendel crossed a pure tall

Pea plant with a pure dwarf Pea plant. All the plants of the Fj generation were tall. On self-breeding plants of the F1 generation, Mendel obtained an F2 progeny of both tall and dwarf in the ratio of 3: 1. The presence of dwarf plants in the F2 generation shows that the factor of dwarfness was present in F1 plants but it did not express its effect due to its recessive nature. The factor for tallness is dominant.

PSEB Class 10 Biology Chapter 9 Heredity

Question 4. The genotype of a plant bearing purple flowers is PP and one with white flowers is pp. When these are crossed

What colour of flowers would you find in F1 progeny?

Give the percentage of white flowers if F1 plants are self-pollinated.

In what ratio would you find PP and Pp in F2 progeny? Draw a flowchart in support of your answer.

Answer:

Purple (b) 25 % (c) 1: 2

Heredity F2 progeny

1 Pure: 2 hybrid purple: 1 pure white

Question 5. Why are some Pea plants tall and others short in nature? Explain with reference the role of genes in controlling characteristics.
Answer:

Genes are segments of DNA. They function in controlling body structure and its working through the synthesis of mRNAs. wRNAs take part in the formation of proteins. The proteins help in the synthesis of enzymes and other biochemicals.

The character of height is controlled by growth hormones. If the gene-controlling height is dominant, it helps in the synthesis of more hormones so that the plant becomes tall. If the gene is recessive, a less efficient protein and a smaller quantity of growth hormones would be produced. As a result, the plant remains dwarf.

Question 6. Explain how Mendel’s experiments show that traits are inherited independently.
Answer:

Mendel performed a dihybrid cross between round yellow-seeded and wrinkled green-seeded Pea plants. In F1 generation he obtained only round yellow seeded plants. Both traits are dominant and are expressed in hybrids.

He raised the F2 generation after the self-breeding of F1 plants. There were four types of F2 plants—round yellow (9/16), round green (3/16), wrinkled yellow (3/16) and wrinkled green (1/16). The combinations of round green and wrinkled yellow-seeded plants were new. They could arise only if the traits of the two characters could assort independently.

Question 7. One plant with dominant tall height bearing purple flowers is crossed with another plant having recessive dwarf and white flowers.

  1. What does the plant’s F1 generation look like?
  2. What type of cross is it?
  3. What is the phenotypic ratio in F2 generation and name the type of plants obtained according to phenotypic ratio?

Answer:

  1. Plants of generation are all tall and purple-flowered.
  2. Dihybrid cross as it involves two different characters.
  3. 9: 3 : 3: 1. Tall and purple flowered (9/16) tall and white flowered (3/16) dwarf and purple flowered (3/16) and dwarf and white flowered (1/16).

Question 8.

1. Name the sex chromosomes present in human males and human females.

2. With the help of a flowchart determine genetically in human beings the sex of the spring if the sperm carrying X chromosome fertilizes the egg.
Answer:

A. Sex chromosomes.

1. Human Male-XY

2. Human female-XX.

B. 22 + X (egg) and 22 + X (sperm) will produce a female baby (44 + XX).

PSEB Class 10 Biology Chapter 9 Question And Answers

Heredity Female Baby

Question 9. Guinea pigs having black colour when crossed with guinea pigs having the same colour produced 100 offspring out of which 75 were black and 25 were white. Now find out :

  1. What is the possible genotype of guinea pigs?
  2. Which trait is dominant and which is recessive?
  3. What is this cross called and what is the ratio of F2 progeny obtained from this cross?

Answer:

  1. Genotype of Guinea Pigs. Bb, Bb.
  2. Black colour is dominant (B) while white colour (b) is recessive.
  3. Monohybrid cross. F2 progeny. 1 pure black (BB): 2 hybrid black (Bb): one white (bb).

Question 10.

  1. Name an animal which can change sex. What does it indicate?
  2. Name the trait which can express itself in the next generation.

Answer:

  1. Ophryotrocha(an annelid). It is male in the young state and female later. Sex is here determined non-genetically.
  2. Dominant trait.

Heredity PSEB Class 10 Notes

Question 11.

  1. Mendel selected the Pea plant for his experiments. List two reasons.
  2. State the meaning of recessive and dominant genes.

Answer:

  • Mendel selected the Pea plant for his experiments because It can be cross-pollinated manually and self-pollinated automatically. It is annual with a short life span and a high yield of seeds.
  • Recessive Gene: It is a gene or factor that cannot express its effect in the presence of its contrasting factor.
    • Dominant Gene: It is a gene or factor which expresses its effect both in homozygous and heterozygous states.

Question 12. In a cross between plants with purple flowers and plants with white flowers, the offspring of the F1 generation had all purple flowers. When F1 generation individuals were self-bred, the F2 generation gave rise to 100 individuals, 75 of which had purple flowers. Make a cross and answer the following.

  1. What is the genotype of F2 individuals?
  2. What is the ratio of purple to white-flowered plants in F2 generation?

Answer:

Heredity Genotypes

1PP (pure purple): 2 Pp (hybrid purple): pp (pure white)

  1. Genotypes of F2 Progeny. 1 PP: 2 Pp: 1 pp.
  2. Purple to white flowered ratio. 75: 25 or 3: 1.

Question 13. A husband has 46 chromosomes. His wife has 46 chromosomes. Then why does not their offspring have 46 pairs of chromosomes which is obtained by fusion of male and female gametes? Support your answer with an illustration.
Answer:

Gametogenesis is not a mitotic division. It is a meiotic division. Therefore, gametes do not possess the same chromosome number as the parents. Instead, they have half the number of chromosomes. As the mother has 46 chromosomes, the ovum will have 23 chromosomes.

Similarly, as the father has 46 chromosomes his sperm will have 23 chromosomes. The fusion of a sperm (23 chromosomes) and an ovum (23 chromosomes) restores the 46 chromosome number in the offspring. There is no chance of having 46 pairs of chromosomes.

PSEB Class 10 Biology Important Questions On Heredity

Heredity pairs Of chromosomes

Question 14. “It is a matter of chance whether a couple will give birth to a boy or a girl”. Justify the statement and support your answer with a neat illustration.
Answer:

The wife produces only one type of ova, that is, 22 + X. The Husband has two kinds of sperm, 22 + X (gymnosperms) and 22 + Y (angiosperms) formed in equal numbers. It is a pure chance which type of sperm comes in contact with the ovum. If it is endosperm, a male child is born. If it is a gymnosperm, a female child is born.

Heredity Neat Illustration

Question 15. A round-seeded plant (RR) Is crossed with a wrinkled-seeded plant (RR). Find out the phenotype and genotype of the F1 and F2 generations.
Answer:

Heredity Phenotype generation

Phenotype of F1 generation = Round Seeded ; Genotype of F, generation = Rr

The phenotype of F2 generation = 3 round: 1 wrinkled

Genotype of F2 generation = 1 pure round (RR): 2 hybrid round (Rr): 1 wrinkled (rr).

Question 16. Mendel studied the inheritance pattern of traits in a Pea plant. According to this study, he obtained a 9 : 3 : 3: 1 ratio of certain traits in the progeny of the F2 generation. Based on it answer these questions.

  1. What traits did he study? How do they represent themselves?
  2. What was the trait of F1 progeny?
  3. Which rule does this inheritance pattern suggest?

Answer:

  1. Mendel crossed round yellow seeded (RRYY) plant with wrinkled green seeded (rryy) plant.
  2. F1 plants were all round and yellow-seeded.
  3. In the F2 generation, four types of plants were formed—round yellow seeded (9/16), round green seeded (3/16), wrinkled yellow seeded (3/16) and wrinkled green seeded (1/16).

The occurrence of round green and wrinkled yellow-seeded plants was a new combination of traits other than the parental types.

This is possible if the traits of the two characters separate or assort independently of each other. The phenomenon is called the law of independent assortment.

PSEB Class 10 Science Chapter 9 Solutions

Question 17. A cross was obtained between a purebred tall Pea plant and a purebred dwarf pea plant and F1 progeny. Later the F1 progeny was selfed to obtain F2 progeny. Answer the following questions :

  1. What is the phenotype of F1 progeny and why?
  2. Give the phenotypic ratio for F2 progeny.
  3. Why is the F2 progeny different from the F1 progeny?

Answer:

  1. F1 progeny is all tall as the trait of tallness is dominant over the trait of dwarfism.
  2. 3 tall: 1 dwarf.
  3. Segregation of the trait of tallness and trait of dwarfism during gamete formation by F1 progeny followed by random fusion of the two types of gametes during the formation of F2 progeny, i.e., T x T (TT), T x t (Tt), t x t (tt).

Question 18. How can you say that in Mendel’s monohybrid cross, the F2 dominants are not the same?
Answer:

Phenotypically F2 dominants appear similar but genotypically they are of two types, pure and hybrid. This can be proved by self-breeding the dominants. One-third of the dominants produce a progeny of only dominants. They are pure for the dominant trait. Two-thirds of the dominants behave as hybrids. They give a progeny of both dominant and recessive traits in the ratio of 3: 1.

Question 19. A cross was made between pure breeding Pea plants one with round and green seeds and the other with wrinkled and yellow seeds.

  1. Write the genotype of Ft progeny. Give reasons for your answer.
  2. Write the different types of F2 progeny obtained along with ratios when F1 progeny was selfed.

Answer:

  1. Across between RRyy and rrYY plants yields an Fj generation ofRrYy(round and yellow seeded plants) even though none of the parents have this set of traits. It is due to the non-expression of recessive alleles for green colour and wrinkled seed in the presence of dominant alleles for yellow colour and round seed.
  2. F2 Progeny. Round yellow (9/16), round green (3/16), wrinkled yellow (3/16) and wrinkled green (1/16).

Question 20. In an experiment, Mendel obtained 1014 plants, out of which 787 had round seeds and 227 had wrinkled seeds in F2 generation.

  1. What is the approximate ratio obtained in F2 generation?
  2. Under which law do you find this ratio?
  3. Why is this law so-called?

Answer:

  1. 787: 227 roughly 3:1.
  2. Law of segregation.
  3. As per the law of segregation, the two alleles of a character separate during gametogenesis and pass to different gametes.
  4. A gamete comes to have only a single allele of a character.

PSEB Class 10 Physics Solutions For Chapter 1 Light-Reflection And Refraction

PSEB Class 10 Physics Solutions For Chapter 1 Light-Reflection And Refraction

Light

Light is the form of energy that enables us to see. An object reflects light that falls on it. We are able to see the object when this reflected light is received by our eyes.

Properties Of Light

  1. Light travels in a straight line. Due to this, light casts a shadow of the object placed in its path.
  2. Light is an electromagnetic wave. It does not require any medium to travel.
  3. The speed of light is maximum in a vacuum. It is 3×108 ms-1.
  4. Light has a dual nature, i.e., particle as well as wave nature.
  5. When light falls on an object, one or more of reflection, refraction, or absorption may happen.

Types Of Materials Based On Absorption Of Light

Three types of materials based on absorption of light are Transparent, Translucent, and Opaque.

PSEB Class 10 Physics Chapter 1 Light-Reflection And Refraction

PSEB Solutions For Class 10 Physics Chapter 1 Types Of Materials Based On Absorption Of Light

Reflection Of Light

The phenomenon of bouncing back of light into the same medium, when it strikes a polished or smooth surface, is called reflection.

Incident Ray = Light ray which falls on the polished or smooth surface

Reflected ray = Light ray that gets bounced back from the polished or smooth surface.

Laws Of Reflection

Applicable to all types of reflecting surfaces, including spherical surfaces

  1. Angle of Incidence (∠i) = Angle of Reflection (∠r)
  2. Incident Ray, Normal to the angle of incidence, and Reflected Ray all lie in the same plane.

PSEB Solutions For Class 10 Physics Chapter 1 Laws Of Reflection

Image– It is the point at which two rays actually meet or appear to meet. An image can be of two types: Real or Virtual.

PSEB Solutions For Class 10 Physics Chapter 1 Image

Characteristics Of the Image Formed By a Plane Mirror

  1. The image formed is Virtual- formed behind the mirror.
  2. Size of image = Size of Object
  3. Distance between mirror and object = Distance between mirror and image
  4. Laterally inverted- means the left side of the object appears right and the right side of the object appears left.

PSEB Solutions For Class 10 Physics Chapter 1 Image Formed By Plane Mirror

Spherical Mirrors

Mirrors whose reflecting surface forms part of the sphere are called spherical mirrors. They are of two types – Concave mirrors and Convex mirrors, as shown below:

PSEB Solutions For Class 10 Physics Chapter 1 Spherical Mirrors

PSEB Solutions For Class 10 Physics Chapter 1 Convex And Concave Mirror

Some Important Terms Used In Context To Spherical Mirrors

PSEB Solutions For Class 10 Physics Chapter 1 Context To Spherical Mirrors

Pole (P) – Centre of the spherical mirror.

Centre of Curvature (C) – The centre of the hollow glass sphere of which the spherical mirror was a part.

Principal Axis – Line joining the pole (P) and centre of curvature (C).

Radius of Curvature (R) – Distance between pole (P) and centre of curvature (C).

Principal Focus (F) – Point on the principal axis where all rays actually meet or appear to meet.

Focal Length (f) – Distance between pole (P) and principal focus (F).

Aperture (MN) – Effective diameter of the spherical mirror.

Relationship Between Focal Length (f) And Radius Of Curvature (R)

Focal Length (f) = Radius of Curvature (R)/2

Rules For Making Ray Diagrams For Spehrical Mirrors

PSEB Solutions For Class 10 Physics Chapter 1 Rules For Making Ray Diagram For Spherical Mirrors

Simple Trick To Remember Image Formation By Concave Mirror

Step 1: Write position of object starting from infinity till between F and P.

Step 2: Write numbers 5, 4, 3, 2, 1 to all positions of object, and numbers 1, 2, 3, 4, 5 to all positions of image. (Note that numbers given to positions of objects are 5-1 and those given to image positions are 1-5. This is important point to be remembered).

Step 3: Comparing the numbers will give us the size of image, For Examle Since1 is very less than 5, size of image will be highly diminished, 2 is less than 4, therefore image will be diminished, and so on (as given in table below).

Note:

  • For object position numbers 5, 4, 3, 2 and 1, image will be real and inverted.
  • Last position of object is an exception- in this case image will be virtual and erect.

image

Simple Trick To Remember Image Formation By Convex Mirror

Important Note: Image formed by convex mirror is always virtual, erect and small in size.

PSEB Solutions For Class 10 Physics Chapter 1 Image Formation By Concave Mirror

PSEB Solutions For Class 10 Physics Chapter 1 Image Formation By Convex Mirror

Uses Of Concave Mirrors

1. Used in torches, search-lights and vehicles headlights to get powerful parallel beams of light as shown in diagram:

PSEB Solutions For Class 10 Physics Chapter 1 Parallel Beams Of Light

2. Used as shaving mirrors to see a larger image of the face, and also used by dentists to see large images of the teeth of patients. For this, the object has to be placed between pole and focus, as shown in figure:

PSEB Class 10 Physics Solutions Chapter 1

PSEB Solutions For Class 10 Physics Chapter 1 Object Has To Be Placed Between Pole And Focus

3. Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces.

4. Used as satellite dish TV antennas as shown in figure:

PSEB Solutions For Class 10 Physics Chapter 1 Satellite Dish TV Antennas

Uses Of Convex Mirrors

1. Used as rear-view (wing) mirrors in vehicles because:

  • They always give an erect, though diminished, image.
  • They have a wider field of view as they are curved outwards, as shown in figure.

PSEB Solutions For Class 10 Physics Chapter 1 Wider View by Convex Mirror

2. Used at blind turns and points of merging traffic to give view of traffic from both sides.

3. Used in shops as security mirror.

New Cartesian Sign Conventions – For Reflection By Spherical Mirrors

In the New Cartesian Sign Convention,

  • Pole (P) of the mirror is taken as the origin.
  • Principal axis of the mirror is taken as the x-axis of the coordinate system.
  • The New Cartesian Sign Convention are summarized in the figure provided below (For details, please refer points 1-5 given after the figure):

PSEB Solutions For Class 10 Physics Chapter 1 The New Cartesian Sign Convention

  1. Object is always placed to the left of the mirror, i.e, light from the object falls on the mirror from the left-hand side.
  2. All distances parallel to the principal axis are measured from the pole of the mirror.
  3. All the distances measured to the right of the origin (along + x-axis) are taken as positive while those measured to the left of the origin (along- x-axis) are taken as negative.
  4. Distances measured perpendicular to and above the principal axis (along + y-axis) are taken as positive.
  5. Distances measured perpendicular to and below the principal axis (along -y-axis) are taken as negative.

Conclusions From New Cartesian Sign Conventions For Spherical Mirrors

Distance of Object from Mirror (u) = Always Negative

Focal length of Concave Mirror (f) = Negative

Focal length of Convex Mirror (f) = Positive

Mirror Formula

It gives the relation between distance of object, distance of image and focal length of the mirror. According to mirror formula

∴ \(\frac{1}{v}+\frac{1}{u}=\frac{1}{f}\)

Where, u = distance of object from pole, v = distance of image from pole, and f = focal length of mirror.

Mirror formula is valid for plane mirrors as well as spherical mirrors for all positions of the object.

Important Note: For solving numerical problems, New Cartesian Sign Conventions must be considered while substituting values for u. v, f (or R. if focal length is calculated using relation f = R/2) in the mirror formula.

Magnification Of Spherical Mirrors

Magnification (m) is defined as the ratio of height of image to the height of object.

∴ \(m=\frac{\text { Height of image }}{\text { Height of object }}=\frac{h_i}{h_o}=-\frac{v}{u}\)

Simple Trick To Find The Type Or Size Of Image From Value Of Magnification

PSEB Solutions For Class 10 Physics Chapter 1 Size Of Image From Value Of Magnification

Important Note:

  • Magnification of convex mirror is always negative.
  • Magnification of concave mirror can be positive or negative depending on the position of the object.

Refraction Of Light

The phenomenon of bending of light when it enters obliquely from one transparent medium into another is called refraction of light. Refraction occurs due to change in speed of light in different media.

Light-Reflection And Refraction PSEB Class 10 Notes

Bending Of Light In Refraction

1. If a ray of light passes from a material in which it travels fast (rarer medium) into a material in which it travels slower (denser medium), then the light ray will bend towards the normal, i.e,

PSEB Solutions For Class 10 Physics Chapter 1 Light In Reflection Fast To Slow

2. If a ray of light passes from a material in which it travels slow (denser medium) into a material in which it travels faster (rarer medium), then the light ray will bend away from the normal.

PSEB Solutions For Class 10 Physics Chapter 1 Light In Reflection Slow To Fast

Simple Trick To Remember The Direction Of Bending Of Light In Refraction

Direction of bending of light in refraction can be easily remembered using the mnemonic “FAST SOFA”

PSEB Solutions For Class 10 Physics Chapter 1 FAST SOFA

3. Extent of bending of incident ray depends upon difference in refractive index between the two medium through which the ray is passing.

4. Emergent Ray is parallel to Incident Ray because the extent of bending of ray of light at the opposite parallel faces of the second medium (glass in this case) is equal and opposite as shown:

PSEB Solutions For Class 10 Physics Chapter 1 Emergent Ray Is Parallel To Incident Ray

5. Perpendicular distance between the incident ray and the emergent ray is called lateral displacement or lateral shift (d). It depends upon:

  • Thickness of the glass slab
  • Refractive index of the glass slab

PSEB Solutions For Class 10 Physics Chapter 1 Lateral Displacement Or Lateral Shift

Refractive Index (n)

It is defined as the ratio of velocity of light in a given pair of media, i.e.,

∴ \(n=\frac{\text { Velocity of light in medium } 1}{\text { Velocity of light in medium } 2}\)

Points To Remember About Refractive Index

  1. Refractive index has no units because it is a ratio.
  2. Refractive index does not depend on the physical density of the medium, For Example kerosene having higher refractive index, is optically denser than water, although its mass density is less than water.
  3. Refractive index of water, nwater= 1.33, and refractive index of air, nair = 1. This means that the ratio of the speed of light in air and the speed of light in water is equal to 1.33.
  4. Refractive index of diamond is highest till date. Its value is 2.42. This means speed of light in diamond is 1/ 2.42 times less than the speed of light in air or vacuum.
  5. n21 means refractive index of 2nd medium with respect to 1st medium, whereas n21 means refractive index of 1st medium with respect to 2nd medium, i.e.,

∴ \(n_{21}=\frac{V_1}{V_2} \quad \text { whereas } \quad n_{12}=\frac{V_2}{V_1}\)

Absolute Refractive Index

It is the ratio of the speed of light in vacuum to the speed of light in the given medium, i.e.,

∴ \(n=\frac{c}{v}\)

where c = 3 x 108 ms-1

Important Note: Absolute refractive index can never be less than 1 because the speed of light in any medium is always less than that in a vacuum.

Optically Rarer And Optically Denser Medium

Optically Rarer Medium – Medium with a lower value of refractive index

Optically Denser Medium – Medium with a higher value of refractive index

For Example – Out of Air and Glass, glass is denser medium while air is rarer medium.

PSEB Class 10 Physics Important Questions Chapter 1

Laws Of Refraction

The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.

The ratio of sine of angle of incidence to the sine of angle of refraction is a constant, for the light of a given colour and for the given pair of media. This law is also known as Snell’s law of refraction. Thus, according to Snell’s law,

∴ \(\frac{\sin i}{\sin r}=\text { constant }\)

The constant value is called the refractive index of the 2nd medium with respect to the 1st medium.

Snell’s law is true for 0 < i < 90°, where “i” is the angle of incidence.

Some Common Examples Of Refraction

  1. The bottom of swimming pool appears higher due to refraction of light on entering water through air.
  2. A pencil partially immersed in water appears to be bent at the interface of air and water.
  3. When a thick glass slab is placed over some printed matter, the letters appear raised.
  4. Lemons placed in a glass tumbler appear bigger.

Spherical Lens – A transparent material bound by two surfaces, of which one or both surfaces are spherical, forms a lens.

Four Types Of Spherical Lens

PSEB Solutions For Class 10 Physics Chapter 1 Four Types Of Spherical Lens

Difference Between Concave Lens And Convex Lens

PSEB Solutions For Class 10 Physics Chapter 1 Difference Between Concave And Convex Lenses

Some Important Terms About Lens

Since both convex and concave lens have two spherical surfaces, it has two centres of curvature and two principal focus.

PSEB Solutions For Class 10 Physics Chapter 1 Two Spherical Surfaces

Centre of Curvature (C)– It is the centre of the sphere of which the lens forms a part. Because a lens has two spherical surfaces, it has two centres of curvature (C1 and C2 as shown in above figures).

Radius of Curvature (R)– It is the radius of the sphere of which the spherical surface of lens forms a part. R1 and R2 are radii of curvature in above figures.

Principal Axis (C1C2 – It is the line passing through the two centres of curvature (C1 and C2) of the lens.

Optical Centre (O) – If a ray of light is incident on a lens such that after refraction through the lens the emergent ray is parallel to the incident ray, then the point at which the refracted ray intersects, the principal axis is called the optical centre of the lens.

Note: Optical centre of lens coincides with the geometric centre of the lens when the radii of curvature of the two surfaces are equal.

Aperture– The diameter of the circular boundary of the lens is called its aperture.

Principal Focus (F)– It is the point through which a parallel light after refraction passes through in the case of a convex lens and appears to pass through in the case of a concave lens. A lens has two focal points, because a lens has two refracting surfaces.

Focal Length (f)– It is the distance of the principal focus from the optical centre of a lens.

1. First Principal Focus (F1) and First Focal Length (f) – It is a fixed point on the principal axis such that rays starting from this point (in convex lens) or appearing to go towards this point (concave lens), after refraction through the lens, become parallel to the principal axis.

PSEB Solutions For Class 10 Physics Chapter 1 First Principal Focus (F1) And First Focal Length (f)

2. Second principal focus (F2) and second focal length (f’)– It is a fixed point on the principal axis such that the light ravs incident parallel to the principal axis, after refraction through the lens, either converge to this point (in convex lens) or appear to diverge from this point (in concave lens).

PSEB Solutions For Class 10 Physics Chapter 1 Second Principal Focus (F2) And Second Focal Length (f')

Important Note: If the medium on both sides of a lens is same, then first and second focal lengths are equal, i.e, f = f.

Rules For Image Formation By Lens

PSEB Solutions For Class 10 Physics Chapter 1 Rules For Image Formation By Lens

Simple Trick To Remember Image Formation By Convex Lens

Step 1: Write position of object starting from infinity till between F and P.

Step 2: Write numbers 1-6 to all positions of object, and numbers 5-1 to all positions of image as shown in figure.

Step 3: Comparing the numbers will give us the size of image, For Example. Since 1 is very less than 5, size of image will be highly diminished, 2 is less than 4, therefore image will be diminished, and so on (as given in table below).

Note:

  • For object position numbers 5-1, image will be real and inverted.
  • Last position of object is an exception- in this case image will be virtual and erect.

This trick will become clear from illustration given below:

PSEB Solutions For Class 10 Physics Chapter 1 Image Formation By Convex Lens

Simple Trick To Remember Image Formation By Concave Lens

Important Note: Image formed by Concave Lens is always Virtual. Erect and Small in size.

PSEB Solutions For Class 10 Physics Chapter 1 Image Formation By Concave Lens

Lens Formula – It gives the relation between distance of object (u), distance of image (v) and focal length (f) for a lens. According to lens formula,

∴ \(\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\)

Note: Lens formula is valid in all situations for all types of spherical lens.

Magnification Of Lens – It is defined as the ratio of the height of an image (hi) to the height of an object (h0). It is also written as ratio of distance of image from optical centre and distance of object from optical centre, i.e,

∴ \(m=\frac{h_i}{h_o}=\frac{V}{u}\)

Simple Trick To Find The Type or Size Of Image From Value Of Magnification

PSEB Solutions For Class 10 Physics Chapter 1 Types Of Image From Value Of Magnification

Power Of Lens (P)– Power (P) of a lens gives the degree of convergence or divergence of light rays achieved by a lens. Power of lens is the reciprocal of its focal length.

∴ \(\text { Power }=\frac{1}{\text { focal length (in meter) }} \mathrm{P}=\frac{1}{f}\)

SI unit of power of a lens is ‘dioptre’ (D). 1 dioptre is the power of a lens having focal length of lm, i.e., ID = lm-1.

PSEB Class 10 Science Chapter 1 Solutions

Points To Remember About Power Of Lens

  1. Power of a Convex Lens = Always positive
  2. Power of Concave Lens = Always Negative.
  3. Opticians use of the term power of lens instead of their focal lengths.
  4. In many optical instruments, number of lenses is combined to increase the magnification and sharpness of the image. In such instruments, the net power (P) of the lenses is given by the algebraic sum of the individual powers PI, P2, P3, … i.e, P = PI + P2 + P3 + …..

Chapter 1 Light-Reflection And Refraction Reason – Assertion Questions And Answers

The following questions consist of two statements- Assertion (A) and Reason (R). Answer these questionsby  selecting the appropriate option given below:

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.

Question 1. Assertion (A): Large concave mirrors are used to concentrate sunlight to produce heat in solar cookers.

Reason (R): Concave mirror converges the light rays falling on it to a point.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 2. Assertion (A): The focal length of the mirror is f and the distance of the object from the focus is u. The magnification of the mirror is f/u.

Reason (R): Magnification = + Size of image/ Size of object

Answer: 3. A is true but R is false.

Question 3. Assertion (A): For observing traffic at back, the driver mirror is a convex mirror.

Reason (R): A convex mirror has a much larger field of view than a plane mirror.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 4. Assertion (A): Higher is the refractive index of a medium or denser the medium, lesser if the velocity of light in that medium.

Reason (R): Refractive index is inversely proportional to velocity.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 5. Assertion: The image formed by a concave mirror is certainly real if the object is virtual.

Reason: The image formed by a concave mirror is certainly virtual if the object is real.

Answer: 3. A is true but R is false.

Question 6. Assertion: The bending of a stick appears to take place by different amounts in different liquids.

Reason: Light is refracted in different media by different amount.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 7. Assertion: A stick partly immersed in water appears to be bent.

Reason: Refraction of light when it passes from water into air.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 8. Assertion: Refractive index of glass with respect to air is different for red light and violet light.

Reason: Refractive index of a pair of media depends on wavelength of light used.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 9. Assertion: When objects are observed through hot air, they appear to be moving slightly.

Reason: The hotter air is optically denser and the colder air is optically rarer.

Answer: 3. A is true but R is false.

Chapter 1 Light-Reflection And Refraction Case Or Source Based Questions And Answers

Question 1. Nalini, a young student, was trying to demonstrate some properties of light in her Science project work. She kept X inside the box (as shown in the figure) and with the help of a laser pointer made light rays pass through the holes on one side of the box. She had a small butterpaper screen to see the spots of light being cast as they emerged.

PSEB Solutions For Class 10 Physics Chapter 1 A Small butter-paper screen To See The Spots Of Light Being Castas They Emerged

1) What could be the ‘X’ that she placed inside the box to make the rays behave as shown?

  1. A converging lens
  2. A parallel-sided glass block
  3. A plane mirror
  4. A triangular prism

Answer: 2. A parallel-sided glass block

2) She measured the angles of incidence for both the rays on the left side of the box to be 48.60. She knew the refractive index of the material ‘X’ inside the box was 1.5. What will be the approximate value of angle of refraction?

  1. 450
  2. 400
  3. 300
  4. 600 (use the value: sin 48.60 = 0.75)

Answer: 3. 300

3) Her friend noted the following observations from this demonstration:

  1. Glass is optically rarer than air.
  2. Air and glass allow light to pass through them with the same velocity.
  3. Air is optically rarer than glass.
  4. Speed of light through a denser medium is faster than that of a rarer medium.

The ratio: sin of angle of incidence in the first medium to the ratio of sin of angle of refraction in the second medium, gives the refractive index of the second material with respect to the first one.

Which one of the combination of the above statements given below is correct.

2, 4 and 5 are correct.

3 and 4 are correct.

1, 4 and 5 are correct.

3 and 5 are correct.

Answer: 4. 3 and 5 are correct.

4) If the object inside the box was made of a material with a refractive index less than 1.5 then the

  1. Lateral shift of the rays would have been less.
  2. Lateral shift of the rays would have been more.
  3. Lateral shift of the rays would remain the same as before.
  4. There is not enough information to comment on any of the above statements.

Answer: 1. Lateral shift of the rays would have been less.

Question 2. A concave mirror has focal length 10 cm. Answer the questions using the following table:

PSEB Solutions For Class 10 Physics Chapter 1 A Concave Mirror Has Focal Length 10 cm

1) If object size is 2 cm, what would be the size of the image in case A?

  1. 2 cm
  2. 10 cm
  3. 4 cm
  4. Less than 2 cm

Answer: 1. 2 cm

2) Nature of the image when u = -15 cm

  1. Virtual and inverted
  2. Real and erect
  3. Virtual and erect
  4. Real and inverted

Answer: 4. Real and inverted

3) Nature of the image in case (D)

  1. Virtual and inverted
  2. Real and erect
  3. Virtual and erect
  4. Real and inverted

Answer: 3. Virtual and erect

4) Position of the image in case (C)

  1. At centre of curvature
  2. At focus
  3. At infinity
  4. Between focus and centre of curvature

Answer: 2. At focus

5) What is the distance at which the centre of curvature located?

  1. 5 cm
  2. 10 cm
  3. 20 cm
  4. 15 cm

Answer: 3. 20 cm

Question 3. An object is placed at the following distances from a convex lens of focal length 15 cm:

  1. 35 cm
  2. 30 cm
  3. 20 cm
  4. 10 cm.

Which position of the object will produce:

1) A magnified real image?

  1. 35 cm
  2. 30 cm
  3. 20 cm
  4. 10 cm

Answer: 3. 20 cm

Here, f = 15cm and 2f = 30cm

Because a magnified real image is formed when the object is placed between f and 2f.

2) A magnified virtual image?

  1. 35 cm
  2. 30 cm
  3. 20 cm
  4. 10 cm

Answer: 4. 10 cm

Because a magnified virtual image is formed when the object is placed between f and the lens.

3) A diminished real image?

  1. 35 cm
  2. 30 cm
  3. 20 cm
  4. 10 cm

Answer: 1. 35 cm

Because a diminished real image is formed when the object is placed beyond 2f.

4) An image of same size as the object?

  1. 35 cm
  2. 30 cm
  3. 20 cm
  4. 10 cm

Answer: 2. 30 cm

Because an image of same size as the object is formed when the object is placed at 2f.

5) At what distance will the image be formed when an object is placed at 30 cm for this converging lens?

  1. 10 cm
  2. 20 cm
  3. 25 cm
  4. 30 cm

Answer: 4. 30 cm

When an object is placed at 2F of converging lens the image will be formed at 2F’ at right side of lens and image formed is real, inverted and of same size.

Question 4. The figure given below illustrates the ray diagram for the formation of image by a concave mirror. The position of the is beyond the centre of the curvature of the concave mirror. On basis of the given figure answer the questions given below.

PSEB Solutions For Class 10 Physics Chapter 1 The Formation Of Image By A Concave Mirror

1) If focal length of the concave mirror is 10 cm, the image formed will be at a distance _______.

  1. Between 10 cm and 15 cm
  2. Between 10 cm and 20 cm
  3. Beyond 20 cm
  4. At 20 cm

Answer: 2. Between 10 cm and 20 cm

Explanation: The focal length of the mirror is 10 cm. This mean, the radius of curvature is 20 cm. From figure, it is clear that the image is formed between the focus and centre of curvature. Thus, the image is formed between 10 cm and 20 cm.

2) In case of concave mirror, the image distance from the pole of the mirror is

  1. Always positive
  2. Always negative
  3. Negative or positive depending upon the position of the object
  4. None of these

Answer: 3. Negative or positive depending upon the position of the object.

3) If the size of the object in the given figure is 5 cm and the magnification produced is – 0.5. The size of the image is

  1. -2.5 cm
  2. -0.1 cm
  3. 2.5 cm
  4. 0.1 cm

Answer: 1. -2.5 cm

= h2/h1; h2 = (- 0.5 x 5)/ 10; h2 =- 2.5 cm

4) A negative sign in the magnification value indicate that the image is

  1. Real and inverted
  2. Real and erect
  3. Virtual and erect
  4. Virtual and inverted

Answer: 1. Real and inverted

5) If the value of magnification is greater than 1 then it indicates that the image formed is

  1. Diminished
  2. The same size as that of the object
  3. Enlarged
  4. Value of magnification cannot specify whether the image is diminished or magnified.

Answer: 3. Enlarged

Question 5. When a spherical mirror is held towards the sun and its sharp image is formed on a piece of carbon paper for some time, a hole is burnt in the carbon paper. Answer the following questions in reference to the above activity.

1) What is the nature of spherical mirror?

  1. Convex mirror
  2. Concave mirror
  3. Plane mirror
  4. Plano convex mirror

Answer: 2. Concave mirror

2) Why is a hole burnt in the carbon paper?

  1. Sun rays are dispersed by the spherical mirror
  2. The Sun’s heat rays are concentrated at the point of sun’s image
  3. Sun rays get diverged after reflection from spherical mirror
  4. Due to atmospheric refraction

Answer: 2. The Sun’s heat rays are concentrated at the point of sun’s image

3) At which point of the spherical mirror the carbon paper is placed?

  1. Between pole and focus
  2. Between centre of curvature and focus
  3. Anywhere between infinity and focus
  4. At focus

Answer: 4. At focus

4) What name is given to the distance between spherical mirror and carbon paper?

  1. Image distance
  2. Object distance
  3. Focal length
  4. Principal axis

Answer: 3. Focal length

5) For the above-mentioned spherical mirror, the image formed by it when the object is placed at its centre of curvature is

  1. Twice the size of the object
  2. Greater than size of object
  3. Equal to the size of the object
  4. Less than the size of the object

Answer: 3. Equal to the size of the object

PSEB Class 10 Biology Solutions For Chapter 1 Life Processes

PSEB Class 10 Biology Solutions For Chapter 1 Life Processes

Life Processes

These are the processes which together perform the functions of growth, repair, and maintenance of living organisms. These include nutrition, digestion, respiration, transportation, and excretion.

Simple Trick To Remember Life Processes

With the help of the mnemonic “MRS GREN” one can easily tell the life processes which indicate whether an organism is alive or not.

  • M: Movement
  • R: Respiration
  • S: Sensitivity (or Feel)
  • G: Growth
  • R: Reproduction
  • E: Excretion
  • N: Nutrition
  • Nutrition

Read And Learn More PSEB Class 10 Biology

Nutration

It is the process by which living organisms take in food, utilizes it to get energy for growth, repair and maintenance, and then excretes the waste material from the body.

Life processes class 10 notes

Simple Trick To Remember Modes Of Nutrition, Its Types And Subtypes

Organisms are divided into two categories, viz. Autotrophs and Heterotrophs on the basis of their mode of nutrition.

PSEB Class 10 Biology Chapter 1 Life Processes

Autotrophs

Plants are Autotrophs. Autotrophs prepare their own food by the process of photosynthesis.

PSEB Solutions Class 10 Biology Chapter 1 Plant Nutrition

Chemical Equation Of Photosynthesis

 

Chemical Equation Of Photosynthesis.

Steps involved in photosynthesis

  1. Absorption of light energy of sun by chlorophyll.
  2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
  3. Reduction of carbon dioxide to carbohydrates.

Heterotrophs

Animals are Heterotrophs. Heterotrophs depend on others for food. They obtain nutrition through process of digestion.

PSEB Solutions Class 10 Biology Chapter 1 Heterophilic Nutrition

  • Digestion is the process of breakdown of complex food molecules into simpler ones.

Tests To Confirm Importance Of Various Raw Materials In Photosynthesis

PSEB Solutions Class 10 Biology Chapter 1 Raw Materials In Photosynthesis

Parts Of Leaf And Their Functions

PSEB Solutions Class 10 Biology Chapter 1 Parts Of Leaf And Their Functions

Summary Of Opening And Closing Of Stomata

Life processes class 10 notes

PSEB Solutions Class 10 Biology Chapter 1 Opening And Closing Of Stomata

Five main factors that determine the opening and closing of stomata are:

  1. Light – Stomata open in blue and red light. This is because blue and red light stimulate the production of malic acid by converting starch into sugar. UV light and green light do not result in stomatal opening because aforementioned conversion does not occur.
  2. Temperature – Stomatal opening is directly proportional to light. Therefore, stomata open in day and close at night.
  3. Carbon Dioxide Concentration – Stomatal opening is inversely proportional to carbon dioxide concentration. Therefore, stomata open at low CO2 concentration, and close at high CO2 concentration.
  4. Water Concentration – Swelling of guard cells due to absorption of water increases turgor pressure resulting in opening of stomatal pores, while shrinking of guard cells due to loss of water closes the stomatal pores (cells become flaccid).
  5. Abscisic Acid (ABA) COncentration – ABA is called the stress hormone of plants. When there is a deficiency of water in leaves. ABA concentration increases leading to closure of stomata. In this way, ABA helps the plant to survive during unfavourable conditions of the environment.

Difference Between Function Of Stomata And Guard Cells

PSEB Class 10 Biology Solutions Chapter 1

PSEB Solutions Class 10 Biology Chapter 1 Difference Between Function Of Stomata And Guard Cells

Flow Chart And Summary Of Holozoic Nutrition

Life processes class 10 notes

PSEB Solutions Class 10 Biology Chapter 1 Holozoic Nutrition

Please Note: See the bracket in above flow chart covers onlyfour steps, i.e., excretion or eaestion is not considered to be a part of nutrition.

  • Ingestion means process of taking in food.
  • Digestion means breaking down of complex food substances into smaller soluble substances with the help of enzymes.
  • Absorption means process by which the products of digestion are absorbed by the blood for supplying to the rest of the body.
  • Assimilation means absorbed food is utilized to provide energy and help in growth and development of cells and tissues.
  • Excretion means removal of undigested waste from the body.

Life processes class 10 full chapter explanation

Holozoic Nutrition In Unicellular Organisms- Amoeba Vs Paramecium

1. Difference Amoeba Vs Paramecium

PSEB Solutions Class 10 Biology Chapter 1 Difference Amoeba Verses Paramecium

2. Similarity Between Amoeba And Paramecium

  • Both follow holozoic mode of nutrition, i.e., in both organisms, the process of nutrition involves ingestion, digestion, absorption, assimilation and egestion.
  • Both organisms undergo intracellular digestion.

Life processes class 10 full chapter explanation

Flow Chart Of Nutrition In Multi-Cellular Organisms- Human Beings

Life Processes PSEB Class 10 Notes

  • In human beings, the nutrition is performed by alimentary canal and the associated glands.
  • Alimentary canal consists of mouth (or buccal cavity), oesophagus (or food pipe), stomach, small intestine, large intestine, rectum and anus.
  • Four Glands associated with the process of nutrition are salivary glands, gastric glands, liver and pancreas.

PSEB Solutions Class 10 Biology Chapter 1 Nutrition In Multi-Cellular Organisms

Flow Chart Showing Dental Caries Or Tooth Decay

  • Dental caries or tooth decay occurs when bacteria acting on sugars produce acids due to which food particles stick to the teeth to form dental plaque.
  • When plaque covers the teeth, saliva (which is alkaline in nature) cannot reach the tooth surface to neutralise the acid.
  • This may cause gradual softening of enamel and dentine.
  • If untreated, microorganisms may invade the pulp, causing inflammation and infection.
  • Dental caries can be prevented by regularly brushing the teeth after eating. This removes the plaque before the bacteria produce acids.

Life processes class 10 full chapter explanation

PSEB Solutions Class 10 Biology Chapter 1 Dental Caries Or Tooth Decay

Starch Iodide Test To Check The Presence Of Starch In Saliva- In this test, when a solution of iodine is added to saliva (containing starch), a blue black colour is obtained as shown in figure:

PSEB Solutions Class 10 Biology Chapter 1 Starch Iodide Test To Check The Presence Of Starch In Saliva

Respiration

It is the process in which oxidation of complex organic substances takes place by taking in oxygen and giving out carbon dioxide to obtain energy in the form of ATP molecules. Respiration is a catabolic process because it involves breakdown of glucose molecules.

Life processes definition and examples

Types Of Respiration

Note: The first step of respiration is same in all the cases, i.e., it involves the break-down of glucose (a 6- carbon molecule) into pyruvate (a 3-carbon molecule). This process takes place in the cytoplasm.

PSEB Solutions Class 10 Biology Chapter 1 Types Of Respiration

Summary Of Three Types Of Glucose Breakdown Pathways

PSEB Solutions Class 10 Biology Chapter 1 Three Types Of Glucose Breakdown Pathways

Flow Chart Of Human Respiratory System

PSEB Solutions Class 10 Biology Chapter 1 Human Respiratory System

Breathing Mechanism In Humans- It is a three-step process.

  • Step 1: Inhalation of oxygen through nostrils.
  • Step 2: Exchange of gases (oxygen and carbon dioxide) takes place in alveoli with the help of respiratory pigment, called hemoglobin.
  • Step 3: Exhalation of carbon dioxide through nostrils.

Life processes definition and examples

PSEB Solutions Class 10 Biology Chapter 1 Breathing Mechanism In Humans

Diagram Showing Exchange Of Gases In Humans

PSEB Class 10 Biology Important Questions Chapter 1

PSEB Solutions Class 10 Biology Chapter 1 Exchange Of Gases In Humans

Transportation

  • In animals,plants,transportation is carried out through the circulatory system which includes the heart, blood, and blood vessels.
  • In plants, it occurs through specialized tissues called xylem(transports water and minerals) and phloem (transports food).

Life processes definition and examples

Blood

Blood is a connective tissue. It performs the functions of transport of food, oxygen and waste materials in the body. Blood has three main components, viz., plasma, blood cells (red and white blood cells), and platelets.

Functions Of Components Of Blood

  1. Plasma- Transport of nutrients, waste products, antibodies, clotting proteins and hormones.
  2. Blood Cells- RBCs (transport of O2 and CO2), WBCs (provide immunity)
  3. Platelets- help in blood clotting.

Difference Between Red Blood Cells (Rbcs) And White Blood Cells (Wbcs)

PSEB Solutions Class 10 Biology Chapter 1 Difference Between Red Blood Cells And White Blood Cells

Points To Remember About Human Heart And Its Functioning

  1. Human heart has four chambers – Two upper chambers (called atria) and two lower chambers (called ventricles).
  2. Atria relax to receive blood from the body whereas ventricles contract to pump blood to different parts/ organs of the body.
  3. Since ventricles have to pump blood into various organs, walls of ventricles are thicker than those of atria.
  4. Valves in the heart ensure that blood does not flow backwards when the atria or ventricles contract.
  5. Blood pressure is the force exerted by blood on the walls of a blood vessel. It is greater in arteries than in veins. Blood pressure of blood inside the artery during ventricular contraction is called systolic pressure and pressure in artery during ventricular relaxation is called diastolic pressure.
  6. Normal systolic pressure is about 120 mm of He and diastolic pressure is 80 mm of He. It is measured with an instrument called sphygmomanometer.

Life processes class 10 diagram

Flow Chart Of Blood Circulation In Human Beings

PSEB Solutions Class 10 Biology Chapter 1 Blood Circulation In Human Beings

Double Circulation In Humans And Its Advantages

In human beings, blood passes through the heart twice during one cardiac cycle. The deoxygenated blood comes to the heart and goes to the lungs for oxygenation. Simultaneously, the oxygenated blood comes to the heart from lungs and goes to different organs.

PSEB Solutions Class 10 Biology Chapter 1 Double Circulation In Humans

Difference Between Pulmonary Circulation And Systemic Circulation

Life processes class 10 diagram

PSEB Solutions Class 10 Biology Chapter 1 Difference Between Pulmonary Circulation And Systemic Circulation

Difference Between Arteries And Veins

PSEB Solutions Class 10 Biology Chapter 1 Difference Between Arteries And Veins

Lymph Or Tissue Fluid

It is a colourless fluid that contains a high concentration of white blood cells and plays an important role in the immune response. It is similar to the plasma of blood but it contains less protein compared to plasma.

Life processes class 10 diagram

Difference Between Blood And Lymph

PSEB Solutions Class 10 Biology Chapter 1 Difference Between Blood And Lymph

Transportation In Plants

Two types of conducting tissues in plants are:

  1. Xylem helps in the transport of water and minerals (obtained from the soil).
  2. Phloem helps in the transport of products of photosynthesis (from leaves to other parts of the plant), respectively.

PSEB Solutions Class 10 Biology Chapter 1 Transportation In Plants

Differences Between Xylem And Phloem

PSEB Solutions Class 10 Biology Chapter 1 Differences Between Xylem And Phloem

Ascent Of Sap – The upward movement of water and minerals from roots to different plant parts is called ascent of sap.

PSEB Solutions Class 10 Biology Chapter 1 Ascent Of Sap

Factors affecting ascent of sap are:

  1. Osmosis- It pushes water from soil to root hair.
  2. Root pressure- It pushes water from root hair to base of stem.
  3. Capillary action- Water rises up to some height of stem due to capillary action.
  4. Adhesion-cohesion of water molecules – Water molecules make a continuous column in the xylem because of these forces.
  5. Transpiration- Loss of water vapour through stomata creates vacuum resulting in suction of water, called transpiration pull. The transpiration pull sucks the water column from the xylem tubes, and thus, water is able to rise to great heights in even the tallest plants.

Life processes class 10 NCERT solutions

Excretion

Excretion is the process of removal of gaseous wastes (produced during photosynthesis or respiration) and nitrogeneous wastes (produced during metabolic activities) from the body of an organism.

PSEB Class 10 Science Chapter 1 Solutions

Mode of excretion depends upon the level of structural organization of the organism.

  • In Unicellular Organisms, they are removed by simple diffusion.
  • In Multicellular Organisms, they are removed by a set of organs which together form the excretory system.

Excretory Organs In Human Beings

Excretory organs in human beings are broadly classified into two categories, viz. main excretory organ (Kidneys) and accessory excretory organs (lungs, liver and skin).

PSEB Solutions Class 10 Biology Chapter 1 Excretory Organs In Human Beings

Points To Remember About Human Excretory System

  1. Nephron is the functional unit of the kidney. It produces urine and cleanses blood by removing waste and excess substances from it. Each kidney has millions of nephrons in it.
  2. Nephron is composed of a renal corpuscle (glomerulus within Bowman’s capsule), a proximal tubule, an intermediate tubule (loop of Henle), a distal convoluted tubule and connecting ducts.
  3. If one kidney is damaged or removed, then the other kidney alone can fulfil excretory needs.
  4. In case of failure of both the kidneys, the function of kidneys needs to be performed artificially with the help of a machine. The process is called hemodialysis.
  5. Function of hemodialysis is similar to kidneys, except that there is no reabsorption involved.
  6. Kidney transplantation is the long term solution in case of failure of both the kidneys.
  7. Kidneys can be donated while the donor is still alive irrespective of his/her age, sex or religion.

Life processes class 10 NCERT solutions

Flow Diagram Of Human Excretory System

PSEB Solutions Class 10 Biology Chapter 1 Human Excretory System

Important Points About Excretion In Plants

Plants use the following ways for excretion:

  1. Gaseous wastes (excess carbon dioxide and oxygen) are excreted through the stomata.
  2. Excess water is excreted by transpiration through stomata.
  3. Many plant waste products are stored in cellular vacuoles in leaves that fall off.
  4. Some waste products are stored as resins and gums, especially in old xylem.
  5. Aquatic plants excrete metabolic wastes through diffusion. Terrestrial plants excrete metabolic wastes into the soil.

Chapter 1 Life Processes Reason- Assertion Questions And Answers

For question provided below, two statements are given—one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (1), (2), (3) and (4) as given below:

  1. Both A and R are true, and R is the correct explanation of the assertion.
  2. Both A and R are true, but R is not the correct explanation of the assertion.
  3. A is true, but R is false.
  4. A is false, but R is true.

Question 1. Assertion: Bile helps in the emulsification of fats.

Reason: Bile makes acidic food coming from the stomach alkaline so that pancreatic enzymes can act on it.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 2. Assertion: Lymph is a light-yellow liquid which flows only in one direction.

Reason: Lymph protects the body by making antibodies.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 3. Assertion: Diffusion does not meet the high energy requirements of multicellular organisms.

Reason: Diffusion is a fast process but only occurs at the surface of the body.

Answer: 3. A is true, but R is false.

Question 4. Assertion: Saliva contains an enzyme called amylase.

Reason: Amylase helps to break down simple sugars like glucose into complex molecules like starch.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 5. Assertion: Phloem tissue transports the food from the leaves to the other parts of the plant.

Reason: The movement of food in phloem takes place by diffusion.

Answer: 3. A is true, but R is false.

Question 6. Assertion: Arteries are thick walled and elastic in nature.

Reason: Arteries have to transport blood away from the heart.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 7. Assertion (A): Plants lack excretory organs.

Reason (R): Plants usually absorb essential nutrients.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 8. Assertion (A): In anaerobic respiration, one of the end product is alcohol.

Reason (R): There is an incomplete breakdown of glucose.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 9. Assertion (A): In plants there is no need of specialised respiratory organs.

Reason (R): Plants do not have great demands of gaseous exchange.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 10. Assertion (A): Bile is essential for digestion of lipids.

Reason (R): Bile juice contains enzymes.

Life processes class 10 questions and answers

Answer: 3. A is true, but R is false.

Question 11. Assertion (A): Carbohydrate digestion mainly takes place in small intestine.

Reason (R): Pancreatic juice contains the enzyme lactase.

Answer: 3. A is true, but R is false.

Question 12. Assertion (A): Aerobic respiration requires less energy as compared to anaerobic respiration.

Reason (R): Mitochondria is the powerhouse of the cell.

Answer: 4. A is false, but R is true.

Question 13. Assertion (A): Human heart is four-chambered.

Reason (R): Vena cava is the only artery that supplies deoxygenated blood to the heart.

Answer: 3. A is true, but R is false.

Question 14. Assertion (A): Energy is required to carry out different life processes.

Reason (R): Energy is obtained in the form of ATP in the mitochondria.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 15. Assertion (A): Rings of cartilage are present in the throat.

Reason (R): These ensure that the air-passage does not collapse.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 16. Assertion (A): Pyruvate is a six-carbon molecule.

Reason (R): It is prepared in the cytoplasm as the first step to cellular respiration.

Answer: 4. A is false, but R is true.

Life processes class 10 questions and answers

Chapter 1 Life Processes Case Or Source Based Question And Answers

Question 1.  The growing size of the human population is a cause of concern for all people. The rate of birth in a given population will determine its size. Reproduction is the process by which organisms increase their population. The process of sexual maturation for reproduction is gradual and takes place while general body is still going on. Some degree of sexual maturation does not necessarily mean that mind or body is ready for sexual acts or for having and bringing up children. Various contraceptive devices are being used by human beings to control the size of population.

1. Which of the following is a common sign of sexual maturation in both boys and girls?

  1. Development of breasts
  2. Growth of pubic hair
  3. Adam’s apple
  4. Broadening of hips

Answer: 2. Growth of pubic hair

2. Which of the following is an IUCD?

  1. Copper-T
  2. Diaphragm
  3. Oral pill
  4. Tubectomy

Answer: 1. Copper-T

3. Which among the following is not a sexually transmitted disease?

  1. Gonorrhoea
  2. AIDS
  3. Syphilis
  4. Cholera

Answer: 4. Cholera

4. A couple wants to space the birth of their second child. Which of the following preventive measure could be taken by the husband?

  1. Oral pills
  2. Diaphragms
  3. Tubectomy
  4. Condoms

Answer: 4. Condoms

Life processes class 10 questions and answers

5. A pregnant woman visits the doctor to determine the sex of the child. Why is she denied of this testing?

  1. It is a complicated test.
  2. It may result in female foeticide.
  3. It is an expensive test.
  4. It is harmful test for the developing foetus

Answer: 2. It may result in female foeticide.

Question 2.  Blood vessels are the channels or conduits through which blood is distributed to body tissues. The vessels make up two closed systems of tubes that begin and end at the heart. One system, the pulmonary vessels, transports blood from the right ventricle to the lungs and back to the left atrium. The other system, the systemic vessels, carries blood from the left ventricle to the tissues in all parts of the body and then returns the blood to the right atrium.

1. Which system carries blood from the right ventricle to the lungs?

  1. Pulmonary
  2. Systemic
  3. Hepatic
  4. Gastric

Answer: 1. Pulmonary

Life processes class 10 important questions

2. Systemic vessels carry blood from:

  1. Right ventricle to lungs
  2. Left ventricle to body tissues
  3. Body tissues to left ventricle
  4. Lungs to right ventricle

Answer: 2. Left ventricle to body tissues

3. Which blood vessels carry blood away from the heart?

  1. Veins
  2. Capillaries
  3. Arteries
  4. Venules

Answer: 3. Arteries

4. The exchange of materials between the blood and tissue cells is done by:

  1. Capillaries
  2. Veins
  3. Venules
  4. Arteries

Answer: 1. Capillaries

5. Which blood vessels carry blood towards the heart?

  1. Veins
  2. Capillaries
  3. Arteries
  4. Venules

Answer: 1. Veins

Life processes class 10 assertion and reason questions

Question 3. The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways – some use oxygen to breakdown glucose completely into carbon dioxide and water, some use other pathways that do not involve oxygen.

1. Which three carbon molecule is formed during the breakdown of glucose?

  1. Lactic acid
  2. Glyceraldehyde
  3. Acetic acid
  4. Pyruvate

Answer: 4. Pyruvate

2. The process in which pyruvate may be converted into ethanol and carbon dioxide is:

  1. Germination
  2. Fermentation
  3. Cellular respiration
  4. Oxidation

Answer: 2. Fermentation

3. Breakdown of pyruvate using oxygen takes place in the:

  1. Cytoplasm
  2. Stroma
  3. Mitochondria
  4. Cellular matrix

Answer: 3. Mitochondria

4. The breakdown of pyruvate in the absence of oxygen producing lactic acid occurs primarily in the:

  1. Muscle cells
  2. Brain cells
  3. Cardiac cells
  4. Nerve cells

Answer: 1. Muscle cells

5. Observe the graph and interpret which of the following is true w.r.t. rate of respiration?

PSEB Solutions Class 10 Biology Chapter 1 Rate Of Respiration

  1. Increases with an increase in temperature
  2. Increases first and then decreases with an increase in temperature
  3. Decreases with an increase in temperature
  4. Decreases first and then increases with an increase in temperature

Answer: 2. Increases first and then decreases with an increase in temperature

Question 4. The human respiratory system consists of a group of organs and tissues that help us to breathe. Lungs are the primary organs of the respiratory system which help in the exchange of gases. The other main parts of this system include a series of airways for air passages, blood vessels and the muscles that facilitate breathing.

Life processes class 10 quick revision

1. Which are the primary organs of respiration in humans?

  1. Lungs
  2. Bronchi
  3. Trachea
  4. Pharynx

Answer: 1. Lungs

2. Nostrils are divided by a framework of cartilaginous structure termed as:

  1. Flaps
  2. Cartilage
  3. Septum
  4. Rings

Answer: 3. Septum

3. Respiration in humans is primarily:

  1. Aerobic
  2. Anaerobic
  3. Partially anaerobic
  4. Partially aerobic

Answer: 1. Aerobic

4. Exchange of gases takes place in the:

  1. Bronchi
  2. Alveoli
  3. Trachea
  4. Bronchioles

Answer: 2. Alveoli

5. The percentage of nitrogen in exhaled air is:

  1. 78%
  2. 0.3%
  3. 21%
  4. 0.03%

Answer: 1. 78%

Question 5. 

PSEB Solutions Class 10 Biology Chapter 1 Cross Section Of Plant Stem Showing Xylem And Phloem

Plants have tissues to transport water, nutrients and minerals. Xylem transports water and mineral salts from the roots up to other parts of the plant, while phloem transports sucrose and amino acids between the leaves and other parts of the plant.

Life processes class 10 quick revision

1. Which of the following processes will not occur in the absence of xylem?

  1. Transport of water
  2. Conduction of food
  3. Transport of minerals
  4. Both a) and c)

Answer: 4. Both a) and c)

2. Transport of food by the phloem is called

  1. Transpiration
  2. Translocation
  3. Guttation
  4. Adhesion

Answer: 1. Transpiration

3. Which of the following is not a characteristic of xylem?

  1. Living cells
  2. Lack of cytoplasm
  3. Impermeable to water
  4. Presence of lignin

Answer: 2. Lack of cytoplasm

4. In phloem, transport occurs between where the substances are made, i.e. ______ and where they are used or stored, i.e. ______

  1. Sink, source
  2. Source, sink
  3. Origin, destination
  4. Destination, origin

Answer: 2. Source, sink

5. ___________ is the process which involves transport of water and minerals.

  1. Transpiration
  2. Translocation
  3. Guttation
  4. Adhesion

Answer: 1. Transpiration

Question 6. The carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis. It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy.

1. Which of the following acts as an internal energy reserve in plants?

  1. Starch
  2. Glycogen
  3. Chitin
  4. Cellulose

Answer: 1. Starch

2. Which of the following processes are not a part of the process of photosynthesis?

  1. Absorption of light energy by chlorophyll
  2. Conversion of light energy to chemical energy and splitting of water molecules
  3. Oxidation of carbon dioxide to carbohydrates
  4. Reduction of carbon dioxide to carbohydrates

Answer: 3. Oxidation of carbon dioxide to carbohydrates

Life processes class 10 quick revision

3. Which of the following structures is absolutely essential for the process of photosynthesis?

PSEB Solutions Class 10 Biology Chapter 1 The Process Of Photosynthesis

  1. Lower epidermis
  2. Chloroplasts
  3. Phloem
  4. Waxy cuticle

Answer: 2. Chloroplasts

4. What is the role of stomata in process of photosynthesis?

  1. Gaseous exchange
  2. Absorption of light
  3. Transfer of nutrients
  4. Emission of light

Answer: 1. Gaseous exchange

Question 7. Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up of calcium phosphate is the hardest substance in the body. It does not dissolve in water, but is corroded when the pH in the mouth is below 5.5. Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. The best way to prevent this is to clean the mouth after eating food. Using toothpastes, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

PSEB Solutions Class 10 Biology Chapter 1 Tooth Decay

1. The tooth decay be prevented:

  1. By rinsing mouth with excess of water after eating.
  2. By using basic toothpaste.
  3. Both (a) and (b)
  4. Preventing use of acidic substances like lemon, etc.

Answer: 3. Both (a) and (b)

2. Teeth enamel is made of a substance called:

  1. Aluminium
  2. Calcium phosphate
  3. Iron
  4. Diamond

Answer: 2. Calcium phosphate

3. Tooth decay in the mouth starts when:

  1. pH of mouth is below 5.5
  2. pH of mouth is 7.6
  3. pH of mouth is 7.5
  4. pH of mouth is 7.52.

Answer: 1. pH of mouth is below 5.5

4. The acidity in the mouth is due to:

  1. Undigestion of food.
  2. Degradation of sugar and food particles remaining in the mouth by bacteria.
  3. Drinking of Mosambi juice.
  4. Eating of acidic substances like tomatoes, oranges etc.

Answer: 2. Degradation of sugar and food particles remaining in the mouth by bacteria.

 

PSEB Class 10 Biology Solutions For Chapter Chapter 5 Our Environment

PSEB Class 10 Biology Solutions For Chapter Chapter 5: Our Environment

Ecosystem

A system consisting of all living organisms and their physical environment, functioning together as a unit, is called an ecosystem.

Flow Chart Of Components Of Ecosystem

PSEB Solutions Class 10 Biology Chapter 5 Components Of Ecosystem

Flow Chart Of Biotic Components

PSEB Solutions Class 10 Biology Chapter 5 Biotic Components

Importance Of Decomposers

  1. Act as Natural Scavengers by disposing of the wastes and dead bodies of plants and animals. In this way decomposers clean the environment and create space for a living of newer generations of organisms.
  2. Help in Maintaining Fertility of Soil by releasing minerals and other raw materials trapped in organic matter into the soil.
  3. Decomposers produce some acids which are useful in solubilization of some minerals.
  4. Decomposers help in recycling the materials in the biosphere.

Types Of Ecosystems

Two types, viz. Natural Ecosystem and Artificial Ecosystem.

PSEB Solutions Class 10 Biology Chapter 5 Types Of Ecosystems

Food Chain

A food chain describes the flow of energy and nutrients through an ecosystem.

Read And Learn More PSEB Class 10 Biology

Important Points About Food Chain

1. Flow of energy in a food chain is unidirectional as shown in diagram.

PSEB Solutions Class 10 Biology Chapter 5 Important Points About Food Chain

2. Each step or level of the food chain forms a trophic level. Flow of energy in trophic levels of a food chain obeys TEN PERCENT LAW.

According to Ten Percent Law law, there is a gradual decrease in the amount of energy transfer from one trophic level to the next trophic level in a food chain, i.e., only 10% of energy is transferred to next trophic level while 90% of energy is used by that particular trophic level in its life processes. This is shown in diagram below:

PSEB Solutions Class 10 Biology Chapter 5 Food Chain

3. Since very less amount of energy is available for the next level of consumers, food chains generally consist of only three or four steps.

4. There are generally a greater number of individuals at the lower trophic levels than at the higher trophic levels.

Food Web – It is defined as a network of organisms which are dependent on each-other.

PSEB Solutions Class 10 Biology Chapter 5 Food Web

Difference Between Food Chain And Food Web

PSEB Solutions Class 10 Biology Chapter 5 Difference Between Food Chain And Food Web

Biological Magnification

The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification.

An example of biological magnification indicating increase in mercury concentration in aquatic life and humans is provided below:

PSEB Solutions Class 10 Biology Chapter 5 Biological Magnification

Since human beings occupy the top level in any food chain, the maximum concentrations of these chemicals get accumulated in our bodies.

Environmental Problems – Two main causes of environmental problems are:

  1. Changes in Environment
  2. Human Activities

Major Environmental Problems

Depletion of Ozone layer and Pollution (Waste or Garbage Disposal).

Ozone Layer Depletion

  • Ozone layer depletion means the thinning of the ozone layer present in the upper atmosphere.
  • The decline of Ozone layer thickness in Antarctica was first discovered in 1985 and was termed as OZONE HOLE.
  • Ozone Layer Depletion primarily occurred due to excessive use of CFCs (Chloro Flouro Carbon. Freon) used as refrigerants and also in fire extinguishers. It also occurs due to environmental pollution.
  • Although ozone is deadly poison, ozone, present at the higher levels of atmosphere, shields the surface of the earth from ultraviolet (UV) radiation from the Sun. Ozone is essential for all aerobic forms of life. Thus, ozone is essential for survival of forms of life in one wav or the other.
  • At the higher levels of the atmosphere, higher energy UV radiations split apart some oxygen molecules (O2) into free oxygen (O) atoms. These atoms then combine with the other oxygen molecules to form ozone.

Ozone

This Ozone, present at the higher levels of atmosphere, shields the surface of the earth from ultraviolet (UV) radiation from the Sun.

However, due to atmospheric pollution, the thickness of the ozone layer is depleting, resulting in poor shielding from UV rays.

Steps Taken To Control Ozone Layer Depletion

In 1987, an agreement was arrived at the United Nations Environment Program (UNEP) with regards to freezing CFC production at 1986 levels.

  1. It is now mandatory for all the manufacturing companies to make CFC-free refrigerators throughout the world.
  2. Modern refrigerators usually use a refrigerant called HFC-134a (1.1,1.2-Tetrafluoroethane) instead of Freon. It does not deplete the ozone layer.

Garbage Disposal

Materials generated during our daily activities and in industrial processes that are not useful to us are called waste materials. They can be broadly categorized into two categories, viz. Biodegradable waste and Non-Biodegradable waste.

Differences Between Biodegradable And Non-Biodegradable Waste

PSEB Solutions Class 10 Biology Chapter 5 Differences Between Biodegradable And Non-Biodegradable Waste

5R’S To Save The Environment

  1. Refuse means “saying no” to the use of materials which have a harmful effect on the environment. For Example. No to plastics.
  2. Reduce means we should minimise our use of natural resources, sources of energy and food materials.
  3. Recycle means that we should collect materials like paper, plastics, glass and metal items. These waste materials should be recycled to obtain these materials again for use.
  4. Reuse means to encourage to use things again and again instead of throwing them away. For Example. plastic bottles .Re-use is better than recycling as it saves energy.
  5. Repurpose means using the waste product if one material as an input material for the production of some other material, For Example. Sugarcane waste obtained from sugar industry is being used for the manufacture of paper.

Chapter 5 Our Environment Reason- Assertion Questions And Answers

Following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:

  1. Both ‘A’ and ‘R’ are true and ‘R’ is correct explanation of the Assertion.
  2. Both ‘A’ and ‘R’ are true but ‘R’ is not correct explanation of the Assertion.
  3. ‘A’ is true but ‘R’ is false.
  4. ‘A’ is false but ‘R’ is true.

Question 1. Assertion (A): Polythene bags and plastic containers are non-biodegradable substances.

Reason (R): They can be broken down by microorganisms in natural simple harmless substances.

Answer: 3. ‘A’ is true but ‘R’ is false.

Question 2. Assertion (A): The concentration of harmful chemicals is least in human beings.

Reason (R): Man is at the apex of the food chain.

Answer: 4. ‘A’ is false but ‘R’ is true.

Question 3. Assertion (A): Ozone is formed in upper atmosphere by 02 in presence of UV radiations.

Reason (R): Ozone depletion will lead to UV rays reaching earth which may cause skin cancer.

Answer: 2. Both ‘A’ and ‘R’ are true but ‘R’ is not correct explanation of the Assertion.

Question 4. Assertion (A): The various components of an ecosystem are interdependent

Reason (R): Food chain and web are formed due to linkage in organisms.

Answer: 1. Both ‘A’ and ‘R’ are true and ‘R’ is correct explanation of the Assertion.

Question 5. Assertion (A): Each step in a food chain is called a trophic level.

Reason (R): Trophic levels are formed by both plants and animals.

Answer: 1. Both ‘A’ and ‘R’ are true and ‘R’ is correct explanation of the Assertion.

Question 6. Assertion (A): Food web consists of only producers.

Reason (R): Specific enzymes are required for breakdown of substances in environment.

Answer: 4. ‘A’ is false but ‘R’ is true.

Question 7. Assertion (A): The function of consumers is to convert organic compound into inorganic compound.

Reason (R): Green plants are called the producers.

Answer: 4. ‘A’ is false but ‘R’ is true.

Chapter 5 Our Environment Case Or Source Based Questions And Answers

Question 1. Plastic bags cause many minor and major ecological and environmental issues. The most general issue with plastic bags is the amount of waste produced. Many plastic bags end up on streets and subsequently pollute major water sources, rivers, and streams. Even when disposed of properly, they take many years to decompose and break down, generating large amounts of garbage over long periods of time. Improperly discarded bags have polluted waterways, clogged sewers and been found in oceans, affecting the ecosystem of marine creatures.

1) Which of the following is non-biodegradable?

  1. Plastic
  2. Tea leaves
  3. Spoilt bread
  4. Paper

Answer: 1. Plastic

2) Which of the following is likely to cause most pollution?

  1. Plastic cups
  2. Paper bags
  3. Dried leaves
  4. Broken glassware

Answer: 1. Plastic cups

3) What is the most general issue with plastic bags?

  1. They are biodegradable
  2. They are heavy
  3. They produce a lot of waste
  4. They are cheaper.

Answer: 3. They produce a lot of waste

4) Which of the following is the effect of plastic pollution?

  1. Clogging of drains
  2. Death of marine life
  3. Loss of aesthetic beauty
  4. All of these

Answer: 4. All of these

5) Which of the following is the most eco-friendly option?

  1. Use of paper bags for shopping
  2. Use of steel plates for dining
  3. Use of kulhads for tea
  4. All of these

Answer: 4. All of these

Question 2. All living things need air to breathe. Contamination of air with particles, gases and chemicals that have the potential to adversely affect the health of humans and animals, vegetation and human assets is called air pollution. Major air pollutants are SO2, nitrogen oxides, CO, CFCs, etc. Refer to the given graph showing air quality of three cities.

PSEB Solutions Class 10 Biology Chapter 5 Air Quality Of Three Cities

  1. What can be inferred from the given graph?
  2. What will be the effect of high concentration of SO2 and NO2 in atmospheric air of city 2?
  3. What are the harmful effects of acid rain?

Answer:

  1. Air of city 2 is most polluted as maximum amount of oxides of sulphur and nitrogen are present in its atmospheric air.
  2. When the rainwater contains large quantities of acids like nitric acid and sulphuric acid formed by dissolution of oxides of nitrogen and sulphur in water it is called acid rain.
  3. Acid rain damages the foliage thereby decreasing the growth and yield of plants. Soil microbes get killed due to low pH of the soil and results in disturbing the terrestrial ecosystem. Buildings and monuments get corroded and damaged.

Question 3. Several interconnected food chains form a food web. A food web is similar to a food chain but the food web is comparatively larger than a food chain. When there are more cross interactions between different food chains, the food web gets more complex. This complexity in a food web leads to a more sustainable ecosystem.

PSEB Solutions Class 10 Biology Chapter 5 Interconnected Food Chains Form A Food Web

1) Which living being occupies the lowest level in the above web?

Plants

Small birds

Frog

Vulture

Answer: 1. Plants

2) What forms the food of a snake?

  1. Frog and small birds
  2. Rat and frog
  3. Small birds and grasshopper
  4. Grasshopper and rat

Answer: 2. Rat and frog

3) Which link would get directly disturbed if the population of grasshopper is wiped out?

  1. Frog
  2. Snake
  3. Vulture
  4. Small birds

Answer: 1. Frog

4) Which organisms in the above food web do not act as herbivores?

  1. Small birds
  2. Grasshoppers
  3. Rat
  4. Snake

Answer: 4. Snake

5) In the given food web, vulture is said to be

  1. Herbivore
  2. Omnivores
  3. Apex carnivore
  4. Producer

Answer: 3. Apex carnivore

Question 4. Raman went to picnic with her friends to a nearby park. All of them took with themselves, eatables packed either in aluminium foils, polythenes, paper bags, plastic bottles, cans or in paper cups. They enjoyed their picnic and when teacher called them to be ready for going back, her friends picked up their bags and left all the waste material scattered here and there. But, Raman called them and asked each one to pick up the left over things and put them in the bins marked ‘biodegradable’ and ‘nonbiodegradable’. She also explained the advantages of doing so. Her friends accepted her advice and cleaned the park. Read the given passage and answer the following questions:

  1. Mention the value reflected by Raman’s initiative.

Answer:

  1. Raman is good observer, takes initiative and a sensible person, who applies and understands the value of nature.

Question 5. Rohit got into a quarrel with some farmers who were spraying DDT in their field. Many people gathered at the spot to see and enjoy the incident. The angry mob demanded that Rohit should not interfere with the farmers’ job. Rohit tried to explain his point and finally succeeded. The farmers gave up spraying DDT.

  1. What did Rohit explain to the farmers?
  2. What is biomagnification? Explain with an example.
  3. What values did Rohit promote?

Answer:

  1. Rohit explained the health hazards of using DDT on our environment and other animals to farmers, i.e. DDT is a non-biodegradable substance and it persists in environment for long time and cause environmental pollution, DDT could enter into a food chain and everyone associated would be affected due to its accumulation in their body.
  2. Biomagnification refers to increase in concentration of the toxicant at successive trophic levels. This happens because this toxic substance gets accumulated in the organism which cannot be metabolised or excreted and is thus, passed onto the next higher trophic level.
  3. Rohit promotes health awareness, eco-friendly nature, sympathy and determination to support the right cause.

 

PSEB Class 10 Biology Solutions For Chapter 4 Control And Coordination

PSEB Class 10 Biology Solutions For Chapter 4: Control And Coordination

Control And Coordination In Animals

In animals, control and coordination is provided by two tissues, viz. Nervous tissues and Muscular tissues.

Read And Learn More PSEB Class 10 Biology

Nervous System- It is made-up of organized network of specialized cells, called nerve cells or neurons which conduct information via electrical impulses from one part of the body to another part of the body.

Neuron- Neuron is the structural and functional unit of nervous system. It consists of three main parts, viz. Dendrites, Cell Body and Axon.

PSEB Class 10 Biology Solutions For Neuron

PSEB Class 10 Biology Solutions For Parts Of Neuron

Types Of Neurons And Their Functions

PSEB Class 10 Biology Solutions For Type Of Neuron And Their Functions

Synapse Or Neuronal Junction – It is the site of transmission of electric nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell.

Pathway Of Nerve Impulse

PSEB Class 10 Biology Solutions For Pathway Of Nerve Impulse

Examples of the two pathways are provided below:

PSEB Class 10 Biology Solutions For Direct Transmission From Relay Neuron To Motor Neuron Through Brain

Diagram Of Synapse And Transmission Of Nerve Impulse At Synapse

PSEB Class 10 Biology Solutions For Synapse And Transmission Of Nerve Impulse At Synapse

Steps involved in the transmission of nerve impulse at synapse are as follows:

  1. Receptors present on dendrites collect information from environment, and set off a chemical reaction that creates an electrical impulse.
  2. This electrical impulse travels to the cell body and then along the axon to its end.
  3. At the end of the axon, the electrical impulse sets off the release of some chemicals.
  4. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. In this way, nervous impulses travel in the body as shown in diagram.
  5. A similar synapse finally allows delivery of such impulses from neurons to muscles cells or glands at the neuromuscular junction.

Release Of Chemicals From Neuron To Muscle Cells At Neuromuscular Junction

PSEB Class 10 Biology Solutions For Release Of Chemicals From Neuron To Muscle Cells At Neuromuscular Junction

Receptors- Receptors are specialized tips of some nerve cells located in our sense organs that detect information from the environment.

Types Of Receptors, Their Location And Functions

PSEB Class 10 Biology Solutions For Types Of Receptors Their Location And Functions

Reflex Action- A quick, sudden and immediate response of the body to a stimulus is called reflex action. Reflex actions are controlled by spinal cord and not by brain, Example

  1. Pulling back of hand on touching a hot object.
  2. Blinking of eyes when bright light is focussed on eyes is also a reflex action. This is controlled by brain. The sequence of events that occur when bright light is focussed on eyes are:

Receptor (receives message) → Sensory neuron → Brain → Motor neuron → Eye → Eye muscle contracts.

Reflex Arc- The pathway through which a nerve impulse travels during a reflex action Is called reflex arc. Nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. Reflex arcs are formed in the spinal cord. Although the information is still sent to the brain, brain doesn’t have a significant response to it.

Stimulus – A stimulus is a thing or an event that evokes a specific functional reaction in an organ or tissue.

Response- The response to a stimulus can be of three main types-

  1. Voluntary Response- Controlled by Fore brain, e.g. running, writing, etc.
  2. Involuntary Response- Controlled by Mid brain and Hind brain, For Example. vomiting, heartbeat, respiration, etc.
  3. Reflex Action- Controlled by Spinal cord. e.g. withdrawal of hand on touching a hot object, blinking of eyes, etc.

Human Nervous System – It consists of two parts, viz. Central Nervous system (CNS) and Peripheral Nervous system (PNS).

PSEB Class 10 Biology Solutions For Human Nervous System

Human Brain

  1. Brain is the main coordinating centre of the body.
  2. It is contained in a bony cage (skull or cranium) which is further filled with cerebrospinal fluid for further shock absorption.
  3. A hard, bumpy structure at the back of the neck (vertebral column or backbone) protects the spinal cord.

PSEB Class 10 Biology Solutions For Human Brain

Flow Chart Of Human Nervous System And Functions Of Parts Of Brain

PSEB Class 10 Biology Solutions For Human Nervous System And Functions Of Parts Of Brain

Flow Chart Of Coordination Between Nervous Tissue And Muscular Tissue

PSEB Class 10 Biology Solutions For Coordination Between Nervous Tissue And Muscular Tissue

When a nerve impulse reaches the muscle, the muscle cells move by changing their shape, i.e., by shortening their length. This shortening of muscle cells occurs due to changes in chemical composition of the proteins present in the muscle cells in response to the stimulus.

Limitations Of Nervous System/ Coordination Through Electrical Impulses

  1. Electrical impulses will reach only those cells that are connected by nervous tissue. Since all cells in the animal body are not connected by nervous tissue, electrical impulses will not be able to reach each and every cell of the body.
  2. Once an electrical impulse is generated in a cell and transmitted, the cell will take some time to reset its mechanisms before it can generate and transmit a new impulse. Therefore, cells cannot continually create and transmit electrical impulses.
  3. Plants do not have any nervous tissue for control and coordination of their movements.

Chemical Communication In Human Beings And Plants

  1. In chemical communication, the cells release a chemical compound (hormone) in response to the stimulus, which diffuses all around the original cell.
  2. The other cells around the cells releasing the hormone have the means to detect, recognise and transmit the hormone using special molecules on their surfaces.
  3. In animals, chemical communication takes place through hormones secreted by various glands of the endocrine system.
  4. Chemical communication is a slower process.
  5. Advantages of chemical communication is that it can potentially reach all cells of the body, regardless of nervous connections, and it can be done steadily and persistently.

Hormones – Hormones are the chemical secretions from the endocrine glands. They are released directly into the blood. Their function is to coordinate growth and activities of the living organisms. The timings and amount of hormone released are regulated by feedback mechanisms, e.g. If the sugar levels in blood rise, it is detected by the cells of the pancreas which respond by producing more insulin. As the blood sugar level falls, insulin secretion is reduced.

Important Human Hormones And Their Functions

PSEB Class 10 Biology Solutions For Important Human Hormones And Their Functions

Adrenaline hormone acts on heart. In emergency situations such as fight or fear adrenaline hormone is secreted which results in faster heart beats, thus, resulting in supply of more oxygen (through blood) to our skeletal muscles. The increase in blood supply to the skeletal muscles is achieved by reducing the blood supply to the digestive system and skin by contraction of muscles around small arteries in these organs. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the emergency situation.

Flow Chart Of Human Endocrine Glands, Hormones And Their Functions

PSEB Class 10 Biology Solutions For Human Endocrine Glands Hormones And Their Functions

Coordination In Plants- Coordination in plants takes place through two types of movements, viz. Nastic Movements and Tropic Movements.

PSEB Class 10 Biology Solutions For Nastic Movements And Tropic Movements

Chemical Communication In Plants- Plant Hormones

Plant Hormones Or Pheromones – These are the chemicals that help in growth, development, coordination and responses to the environmental changes in plants.

PSEB Class 10 Biology Solutions For Plant Hormone And Function

Simple Trick To Learn Plant Hormones And Their Functions

Remember the mnemonics “A CAGE” for sequence of plant hormones and “Go Come Ate Sleep Repeat” for the functions of plant hormones. Now using these two mnemonics, we can write the functions of all plant hormones as follows:

PSEB Class 10 Biology Solutions For Plant Hormone And Functions

Flow Chart Of Plant Growth Promoters And Inhibitors

PSEB Class 10 Biology Solutions For Plant Growth Promoters And Inhibitors

Chapter 4 Control And Coordination Case or Source Based Questions And Answers

Question 1.

PSEB Class 10 Biology Solutions For A Growth Movement Of A Plant Parts

A growth movement of a plant part in response to an external stimulus in which the direction of stimulus determines the direction of response is called tropism. Thus, tropism is a directional movement of the part of a plant caused by its growth. The growth of a plant part in response to a stimulus can be towards the stimulus (in the direction of stimulus) or away from the stimulus (against the direction of stimulus) due to which we can have a positive tropism or negative tropism, respectively.

1. If the growth (or movement) of a plant part is towards the stimulus, it is called ______ tropisim.

  1. Positive
  2. Negative

Answer: 1. Positive

2. If the growth (or movement) of a plant part is away from the stimulus, then it is called ______ tropisim.

  1. Positive
  2. Negative

Answer: 2. Negative

3. The bending of the plant stem (or shoot) towards light is actually ______ phototropism.

  1. Positive
  2. Negative

Answer: 1. Positive

4. Tropism is a directional movement of the part of a plant caused by its growth.

  1. True
  2. False

Answer: 2. False

Question 2. To carry out a simple function such as eating food there has to be coordination of the eyes, hands and the mouth. The eyes have to focus on the food, the hands have to pick it up and take it to the mouth where it will be chewed. All these actions have to be coordinated in such a manner that they follow a particular sequence and the action is completed. A similar mechanism is also needed for internal functions of the body.

This function is carried out by the nervous system. It is composed of (a) Specialised cells which can detect, receive and transmit different kinds of stimuli. These are called neurons, (b) Nerve fibres which are certain bundles of extended processes of nerve cells. The individuals also have to adjust to the changing conditions around them and vary their responses. At the same time, the internal conditions of the body should be maintained constant. This is called homeostasis. The internal conditions of the body are maintained at a constant by controlling the physiology of the organisms.

1. What will the correct sequence in which conduction of information through nerves take place?

Answer: Dendrites → Cell body Axon → Nerve endings at the tip of axon → Synapse → Dendrite of next neuron

2. How homeostasis is said to maintain the equilibrium of the body?

Answer: Homeostasis helps in keeping the constant internal environment within a cell or a body and hence maintains the equilibrium of the body

3. What function does the central nervous system perform?

Answer: The central nervous system is comprised of the brain and the spinal cord which process the information received from the receptors on/in the body.

4. What happens when the dendrite tip of a nerve cell receives a signal?

Answer: Upon receiving a signal, the dendrite tip of a nerve cell sets off a chemical reaction which creates an electrical impulse in the them.

Question 3. The neural system of all animals is composed of highly specialised cells called neurons which can detect, receive and transmit different kinds of stimuli. The neural organisation is very simple in lower invertebrates. For example, in Hydra it is composed of a network of neurons. The neural system is better organised in insects, where a brain is present along with a number of ganglia and neural tissues. The vertebrates have a more developed neural system.

The human neural system is divided into two parts

  • The central neural system (CNS)
  • The peripheral neural system (PNS)

The CNS includes the brain and the spinal cord and is the site of information processing and control. The PNS comprises of all the nerves of the body associated with the CNS (brain and spinal cord). The nerve fibres of the PNS are of two types: Afferent fibres and Efferent fibres.

The afferent nerve fibres transmit impulses from tissues/organs to the CNS and the efferent fibres transmit regulatory impulses from the CNS to the concerned peripheral tissues/organs. The PNS is divided into two divisions called somatic neural system and autonomic neural system.

The somatic neural system relays impulses from the CNS to skeletal muscles while the autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body. The autonomic neural system is further classified into sympathetic neural system and parasympathetic neural system. Visceral nervous system is the part of the peripheral nervous system that comprises the whole complex of nerves, fibres, ganglia, and plexuses by which impulses travel from the central nervous system to the viscera and from the viscera to the central nervous system.

1. The afferent nerve fibres transmit impulses from __________

  1. Tissues to the CNS
  2. Organs to the CNS
  3. CNS to tissues
  4. Both a and b

Answer: 4. Both a and b

2. The efferent nerve fibres transmit impulses from __________

  1. Tissues to the CNS
  2. Organs to the CNS
  3. CNS to tissues
  4. Organ to organ

Answer: 3. CNS to tissues

3. How many types of nerve fibres do PNS have? Name them.

Answer: The nerve fibres of the PNS are of two types: Afferent fibres and Efferent fibres

4. Give the divisions of peripheral nervous system and their function?

Answer: The PNS is divided into two major divisions called somatic neural system and autonomic neural system. The somatic neural system relays impulses from CNS to the skeletal muscles while ANS transmits impulses from CNS to the smooth muscles.

5. How impulses travel from the central nervous system to the viscera and from the viscera to the central nervous system?

Answer: Visceral nervous system is the part of the peripheral nervous system that comprises the whole complex of nerves, fibres, ganglia, and plexuses by which impulses travel from the central nervous systemtet/?ewsceraandfromMe viscera to the centrafnervous system.

Question 4.

PSEB Class 10 Biology Solutions For A Nerve Impulse

 

A nerve impulse is transmitted from one neuron to another through junctions called synapses. A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, which may or may not be separated by a gap called synaptic cleft. There are two types of synapses, namely, electrical synapses and chemical synapses. At electrical synapses, the membranes of pre- and post-synaptic neurons are in very close proximity. Electrical current can flow directly from one neuron into the other across these synapses. Transmission of an impulse across electrical synapses is very similar to impulse conduction along a single axon. Impulse transmission across an electrical synapse is always faster than that across a chemical synapse. Electrical synapses are rare in our system.

At a chemical synapse, the membranes of the pre- and post-synaptic neurons are separated by a fluidfilled space called synaptic cleft. Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses. The axon terminals contain vesicles filled with these neurotransmitters. When an impulse (action potential) arrives at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane where they fuse with the plasma membrane and release their neurotransmitters in the synaptic cleft. The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the post-synaptic neuron. The new potential developed may be either excitatory or inhibitory.

1. Impulse transmission across an electrical synapse is always

  1. Slower than
  2. Faster than
  3. Greater than
  4. Leaser than

Answer: 2. Faster than

2. Identify the incorrect statement

Statement 1- Impulse transmission across an electrical synapse is always slower.

Statement 2- A nerve impulse is transmitted from one neuron to another through junctions.

Statement 3- Electrical synapses are common in our system.

Statement 4- Chemical synaptic neurons are separated by synaptic cleft.

  1. Only 1
  2. Both 2 & 3
  3. Only 3
  4. None of the above

Answer: 1. Only 1

3. Give the name of components by which synapses is formed?

Answer: Synapse is formed of the membranes of a pre-synaptic neuron and a post-synaptic neuron, this membrane may or may not be separated by a gap called synaptic cleft,

4. Explain how neurotransmitters are released in synaptic cleft?

Answer: When an impulse comes at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane where they fuse with the plasma membrane and release their neurotransmitters in the synaptic cleft.

5. How action potential is responsible for the formation of new potential?

Answer: When an action potential arises at the axon terminal, it stimulates the movement of the synaptic vesicles towards the membrane and release their neurotransmitters in the synaptic cleft. The released neurotransmitters bind to their specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the post-synaptic neuron. The new potential developed may be either excitatory or inhibitory.

PSEB Class 10 Biology Solutions For Chapter 2 How Do Organisms Reproduce?

PSEB Class 10 Biology Solutions For Chapter 2: How Do Organisms Reproduce?

Reproduction

The process by which living organisms produce new individuals similar to themselves is called reproduction. It can occur in two ways – Asexual and Sexual.

Difference Between Asexual And Sexual Reproduction

PSEB Solutions Class 10 Biology Chapter 2 Difference Between Asexual And Sexual Reproduction

Note:

  • Both kind of reproduction, i.e., asexual and sexual, can take place both in unicellular and multicellular organisms.
  • Irrespective of the type by which an organism reproduces, the first step in reproduction always involves division of nucleus. This is followed by division of cytoplasm.

Life processes class 10 notes

Advantages Of Sexual Reproduction

  1. Variations In Characters- Since sexual mode of reproduction allows more variation, and variations ensure survival of species in changing environments, sexual mode of reproduction is beneficial and desirable.
  2. Ability To Adapt In Changing Environments – More variations means greater ability to adapt in changing environments, which in turn is beneficial for survival.
  3. Evolution of New Traits – Variations in genetic material (characters) arise due to errors in DNA copying mechanism. In this way, each new variation is made in a DNA copy that already has variations accumulated from previous generations. Combining variations from two or more individuals leads to creation of new combinations leading to evolution of species.
  4. Suppression of Harmful Traits – During DNA copying, the harmful traits often remain naturally suppressed due to reshuffling of gene pairs that occur during formation and fusion of gametes.

PSEB Class 10 Biology Solutions Chapter 2

Read And Learn More PSEB Class 10 Biology

Limitations Of Sexual Reproduction

  1. It takes time and energy to find a mate and reproduce.
  2. Reproduction through sexual means is uncertain as some mates may be infertile or fertilization of gametes may not occur despite numerous attempts.
  3. Favourable genetics might not be passed to the offspring.
  4. Fewer offspring are typically produced.

Asexual Reproduction In Unicellular Organisms

PSEB Solutions Class 10 Biology Chapter 2 Asexual Reproduction In Unicellular Organisms

PSEB Solutions Class 10 Biology Chapter 2 Asexual Reproduction In Multicellular Organisms

Advantages Of Vegetative Propagation

  1. Vegetative propagation is used to grow many plants like sugarcane, roses, or grapes for agricultural purposes.
  2. Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.
  3. Vegetative propagation is useful for propagation of plants such as banana, orange, rose and jasmine that have lost the capacity to produce seeds.
  4. All plants produced by vegetative propagation are genetically similar to the parent plant and have all its characteristics.

Life processes class 10 PSEB solutions

Maintenance Of Number Of Chromosomes In Sexual Reproduction

Maintenance of number of chromosomes in sexual reproduction occurs with the help of meiosis. Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information.

PSEB Solutions Class 10 Biology Chapter 2 Maintenance Of Number Of Chromosomes In Sexual Reproduction

  • Sexually reproducing organisms have two kinds of cells, viz. somatic cells (or non-reproductive cells) and reproductive cells.
  • Somatic cells have 22 pairs of chromosomes – one member of each pair comes from father and the other comes from mother, i.e., somatic cells are diploid in nature.
  • Reproductive cells (called gametes) have only half the number of chromosomes and half the amount of DNA as compared to somatic cells, i.e., reproductive cell is haploid in nature.
  • Reduction in number of chromosomes in reproductive cells is achieved by meiosis.
  • Two different reproductive cells (one male and the other female) unite together (n+n) to form a zygote (2n). In humans, each gamete (egg and sperm) contains 23 chromosomes, and the zygote formed by their union has 23+23 = 46 chromosomes, thereby resulting in re-establishment of the number of chromosomes and the DNA content in the new generation.

Life processes class 10 PSEB solutions

Parts Of A Flower And Their Functions

PSEB Solutions Class 10 Biology Chapter 2 Parts Of Flower

PSEB Solutions Class 10 Biology Chapter 2 Parts Of Flower And Their Functions

How Do Organisms Reproduce PSEB Class 10 Notes

Steps Involved In Reproduction In Flowering Plants (Angiosperms)

PSEB Solutions Class 10 Biology Chapter 2 Steps Involved In Reproduction In Flowering Plants (Angiosperms)

  • Reproduction in flowering plants begins with pollination, the transfer of pollen from anther to stigma of the flower.
  • If the transfer takes place to the stigma of flower of the same plant, it is called self-pollination.
  • If the transfer takes place to the stigma of flower of another plant, it is called cross-pollination.
  • Once the pollen grain reaches the stigma, a pollen tube grows from the pollen grain to an ovule.
  • Two sperm nuclei develop. One of them unites with the egg nucleus and produces a zygote. The other unites with two polar nuclei to produce an endosperm that stores food for the development of a plant.
  • Zygote develops into seed and seedling.

Life processes class 10 PSEB solutions

Male And Female Reproductive Organs Of Flowering Plants (Angiosperms)

PSEB Solutions Class 10 Biology Chapter 2 Male And Female Reproductive Organs Of Flowering Plants (Angiosperms)

Five Stages In Germination Of Seed

PSEB Solutions Class 10 Biology Chapter 2 Five Stages In Germination Of Seed

  1. Water fills the seed. This is called Imbibition.
  2. Water activates the enzymes that begin the growth of the plant.
  3. Seed grows a root to access water underground.
  4. Seed grows shoots that grow towards the sun.
  5. Shoots grow leaves, etc.

Life processes class 10 extra questions

Difference Between Self-Pollination And Cross-Pollination

PSEB Solutions Class 10 Biology Chapter 2 Difference Between Self Pollination And Cross Pollination

Difference Between Radicle And Plumule

PSEB Solutions Class 10 Biology Chapter 2 Difference Between Radicle And Plumule

Points To Remember About Sexual Reproduction In Human Beings

  • Human beings become reproductively active from the onset of puberty.
  • Puberty is the period during adolescence when the rate of general body firowth begins to slow down and reproductive tissues begin to mature. A boy or girl becomes sexually mature in puberty.
  • Puberty is a slow process spread over months and years. This is because while the body of the individual organism is growing to its adult size, the resources of the body are mainly directed at achieving this growth. While that is happening, the maturation of the reproductive tissue is not likely to be a major priority.
  • Onset of puberty in males occurs between 11 to 13 years of age, while in females it occurs between 10 to 12 years of age.
  • Puberty is associated with many physical, mental, emotional and psychological changes.

PSEB Class 10 Biology Important Questions Chapter 2

Life processes class 10 MCQ with answers

The physical changes that occur during puberty are called secondary sexual characters.

  • Secondary sexual characters common to both boys and girls – Growing of thick dark hair in arm pits and genital area; appearance of thinner hair on legs, arms and face; skin becomes oily and appearance of pimples on face.
  • Secondary sexual characters that occur only in boys – Appearance of beard and moustache, voice begins to crack, reproductive organs develop and start producing releasing sperms, penis occasionally begins to become enlarged and erect.
  • Secondary sexual characters that occur only in girls – Increase in breast size, darkening of the skin of nipples, and start of menstruation.

Life processes class 10 MCQ with answers

Parts Of The Male Reproductive System And Their Functions

PSEB Solutions Class 10 Biology Chapter 2 Parts Of Male Reproductive System

PSEB Solutions Class 10 Biology Chapter 2 Parts Of Male Reproductive System And Their Functions

Parts Of The Female Reproductive System And Their Functions

PSEB Solutions Class 10 Biology Chapter 2 Parts Of Female Reproductive System

PSEB Solutions Class 10 Biology Chapter 2 Parts Of Female Reproductive System And Their Function

Steps Involved In Reproduction In Human Beings

PSEB Solutions Class 10 Biology Chapter 2 Steps Involved In Reproduction In Human Beings

  1. In Males, testes produce male gametes (sperms).
  2. In Females, ovaries produce female gametes (ova).
  3. During sexual intercourse, sperms enter the vaginal passage and travel upwards to reach the oviduct. Here, they may encounter the egg, and fertilization may occur. Fertilisation occurs in the fallopian tube. Fertilization is the process of fusion of nuclei of the sperm and egg.
  4. After fertilization, zygote is formed. A fertilized egg is called a zygote.
  5. The zygote starts dividing and form a ball of cells and tissues called embryo.
  6. The embryo is implanted in the inner lining of the uterus (called endometrium; Endometrium is richly supplied with blood vessels and provides nutrients for the growing embryo) where the embryo continues to grow and develop organs to become foetus (When all body parts of the embryo can be fully identified, it called foetus).
  7. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. Placenta is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.
    • Functions of Placenta include:
      • Providing nutrition to the growing embryo from the mother’s blood.
      • Removal of waste substances by transferring them into the mother’s blood.
  8. The development of the child inside the mother’s body takes approximately nine months.
  9. The child is born as a result of rhythmic contractions of the muscles in the uterus.

Life processes definition and examples

Difference Between Zygote, Embryo And Fetus

PSEB Solutions Class 10 Biology Chapter 2 Difference Between Zygote Embryo And Fetus

Menstruation

It is the monthly process of shedding of the lining of a woman’s uterus as blood and mucus along with the unfertilized ovum and the ruptured cells and tissues of the endometrium through the vagina of the female. Menstruation occurs if fertilization of egg does not occur. It is a 28-dav cycle which occurs in every reproductively active female (from puberty). The flow of blood continues for 2 to 8 days.

PSEB life processes class 10 questions answer

Difference Between Menarche And Menopause

PSEB Solutions Class 10 Biology Chapter 2 Difference Between Menarche And Menopause

Comparison Between Sexual Reproductive System Of Plants And Animals

PSEB Solutions Class 10 Biology Chapter 2 Comaprison Between Sexual Reproductive System Of Plants And Animals

Reproductive Health

Reproductive health refers to a state of complete physical, mental and social well-being of males and females during their entire reproductive age. The physical well-being refers to healthy reproductive organs and healthy hormone producing glands.

Reproductive health is important because it protects both the mother and the child from infectious diseases. It also ensures delivery of a healthy baby.

Four pillars of reproductive health are:

  1. Responsible Parenthood
  2. Respect for Life
  3. Birth Spacing
  4. Informed Choice – Informed choice means giving options to a person to choose from several diagnostic tests or treatments, knowing the details, benefits, risks and expected outcome of each.

PSEB life processes class 10 questions answer

Sexually Transmitted Diseases (STDs) – Sexually transmitted diseases can be bacterial or viral.

Bacterial STDs – Gonorrhoea and Syphilis.

Viral STDs – Warts and HIV-AIDS.

Birth Control Measures – Birth control measures means methods to prevent pregnancy. Birth control measures are important for facilitating family planning/spacing of births, reducing unintended pregnancies and abortions. They provide both health and social benefits to mothers and their children.

PSEB Class 10 Science Chapter 2 Solutions

Types Of Birth Control Measures

PSEB Solutions Class 10 Biology Chapter 2 Types Of Birth Control Measures

Chapter 2 How Do Organisms Reproduce Reason- Assertion Questions And Answers

For question provided below, two statements are given—one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

  1. Both A and R are true, and R is the correct explanation of the assertion.
  2. Both A and R are true, but R is not the correct explanation of the assertion.
  3. A is true, but R is false.
  4. A is false, but R is true.

Question 1. Assertion: Sexual reproduction generates recombination.

Reason: Sexual reproduction involves crossing over.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 2. Assertion: Reproduction enables the continuity of life for generations.

Reason: Reproduction is a biological process in which an organism gives rise to young ones similar to itself.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 3. Assertion: Sexual reproduction generates recombination.

Reason: Sexual reproduction involves crossing over

PSEB life processes class 10 questions answer.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 4. Assertion: Asexual reproduction requires only female animals.

Reason: Male animals are not capable for asexual reproduction.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 5. Assertion: The zygote developed from sexual reproduction is diploid.

Reason: In sexual reproduction, haploid gametes fuse and form zygote.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 6. Assertion (A): Spores are unicellular bodies.

Reason (R): The parent body simply breaks up into smaller pieces on maturation.

Answer: 3. A is true, but R is false.

Question 7. Assertion (A) : The offspring produced by sexual reproduction is likely to adjust better in environmental fluctuation.

Reason (R): During the fusion of gametes there is mixing of genetic material from two parents.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 8. Assertion (A): Testes lie in penis outside the body.

Reason (R): Sperms require temperature lower than the body temperature for development.

Answer: 4. A is false, but R is true.

Question 9. Assertion (A): Amoeba reproduces by fission.

Reason (R): All unicellular organisms reproduce by asexual reproduction.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Chapter 2 How Do Organisms Reproduce Case Or Source-Based Questions

Question 1. Contraception is an artificial method or other techniques, mainly used to prevent pregnancy as a consequence of sexual intercourse. When a sperm reaches the ova in women, she may become pregnant. Contraception is a method that prevents this phenomenon by stopping the egg production or by keeping the egg distinct from the sperm or by stopping the fertilized egg attaching to the lining of the womb.

  1. What happens if an egg is not fertilized?
  2. How does the embryo get nourishment inside the mother’s body?
  3. Why do we need to adopt contraceptive measures?
  4. How does contraception work?

Answer:

  1. If an egg is not fertilized by a sperm then blood along with cellular debris comes out through the vagina and this process is called menstruation.
  2. The embryo gets nourishment inside the mother’s body with the help of placenta
  3. We need to adopt contraceptive measures:
    1. To prevent unwanted pregnancies,
    2. To prevent sexually transmitted diseases,
    3. Spacing between children
  4. Contraception is a method that prevents unwanted pregnancies by stopping the egg production or by keeping the egg distinct from the sperm or by stopping the fertilized egg attaching to the lining of the womb.

Question 2. Different organisms reproduce in a different manner. The modes by which various organisms reproduce depend on the body design of the organisms.

Life processes class 10 MCQ with answers

1. Splitting up of a single cell into exactly two daughter cells occurs in:

  1. Multiple fission
  2. Binary fission
  3. Regeneration
  4. Segmentation

Answer: 2. Binary fission

2. Multiple fission occurs in:

  1. Paramoecium
  2. Euglena
  3. Leishmania
  4. Plasmodium

Answer: 4. Plasmodium

3. Spirogyra reproduces by:

  1. Fragmentation
  2. Fission
  3. Budding
  4. Regeneration

Answer: 1. Fragmentation

4. Regeneration is carried out by specialised cells called

  1. Bud cells
  2. Regenerative cells
    Stem cells
  3. Proliferative cells

Answer: 3. Stem cells

5. Which mode of reproduction is seen in the given picture?

PSEB Solutions Class 10 Biology Chapter 2 Mode Of Reproduction And Regeneration

  1. Budding
  2. Regeneration
  3. Fission
  4. Segmentation

Answer: 2. Regeneration

Question 3. The most obvious outcome of the reproductive process still remains the generation of individuals of similar design. The rules of heredity determine the process by which traits and characteristics are reliably inherited.

1. Which type of reproduction would give rise to exact copies of parents?

Answer: Asexual Reproduction

2. The visible characteristic in an organism is known as:

  1. Prototype
  2. Stereotype
  3. Phenotype
  4. Genotype

Answer: 3. Phenotype

Life processes class 10 MCQ with answers

3. A plant with two ‘small’ genes breeds with a plant with two ‘tali’ genes to produce:

  1. Small plants and tall plants in the ratio 1:3
  2. All small plants
  3. All tall plants
  4. Tall plants and small plants in the ratio 3:1 17

Answer: 3. All tall plants

4. What are the “Factors” that Mendel talked about in his experiment?

  1. RNA Fragments
  2. Protein chains
  3. Similar forms of single gene
  4. Contrasting forms of single gene

Answer: 4. Contrasting forms of single gene

5. Offspring formed as a result of sexual reproduction exhibit more variations because

  1. Sexual reproduction is a lengthy process
  2. Genetic material comes from a single parent
  3. Genetic material comes from two parents of different species
  4. Genetic material comes from many parents

Answer: 3. Genetic material comes from two parents of different species

 

PSEB Class 10 Biology Solutions For Chapter 3 Heredity And Evolution

PSEB Class 10 Biology Solutions For Chapter 3: Heredity And Evolution

Heredity

Heredity means transmission of characters (traits) from parents to offsprings. These can be physical traits (e.g. eye colour, blood type or a disease), or behavioural traits.

Genetics- Branch of science that deals with heredity and variation.

Read And Learn More PSEB Class 10 Biology

Three Reasons For Variations During Reproduction

  1. Errors in DNA copying.
  2. Random fertilization.
  3. Crossing over during meiosis.

Reason For Variations In Asexual Reproduction

  1. Variations occur only due to defects in DNA copying.
  2. Since only one parent is involved, the genetic materials are transferred from only one parent. As a result, the frequency of variation among offspring is very less.

PSEB Solutions Class 10 Biology Chapter 3 Reason For Variations In Asexual Reproduction

Reasons For Variations In Sexual Reproduction

  1. Variations can occur due to one or more of the following reasons – errors in DNA copying, random fertilization, crossing over during meiosis.
  2. Since gametes from two separate people are fused, variations take place at a higher frequency.

PSEB Solutions Class 10 Biology Chapter 3 Reasons For Variations In Sexual Reproduction

Mendel’s Contribution- Rules Of Inheritance Based On Experiments On Garden Peas

  1. Characters are transferred from the parents to the offsprings through genes. These genes are present in the DNA molecules in the chromosomes.
  2. Both the father and the mother contribute equal amounts of genetic material to the child. This means that each trait can be influenced by both paternal and maternal DNA. Thus, for each trait there will be two versions (one from the father and the other from the mother) in each child.

Simple Trick To Remember Seven Pairs Of Contrasting Characters Selected By Mendel

With the help of the mnemonic “SSCCPPF” one can easily remember the seven pairs of contrasting characters selected by Mendel for conducting experiments on pea plants

PSEB Solutions Class 10 Biology Chapter 3 Seven Pairs Of Contrasting Characters Selected By Mendel

Mendel’s Experiments- Monohybrid Cross

  1. Cross pollination of plants having one pair of characters- a pure tall pea plant (TT) and a pure dwarf pea plant (tt).
  2. F1 generation- All tall plants were obtained.
  3. Self-pollination of plants of FI generation.
  4. F2 generation – Tall and dwarf plants obtained in the ratio 3:1 (Phenotypic ratio) and 1:2:1 :: TT: Tt: tt (Genotypic ratio).
  5. Trait expressed in FI generation is dominant trait, while the trait suppressed in FI generation is recessive trait.

PSEB Solutions Class 10 Biology Chapter 3 Mendel's Experiments Monohybrid Cross

Mendel’s Experiments- Dihybrid Cross

  1. Cross pollination of plants having two pairs of characters, viz. colour and shape of seeds, i.e, Round Yellow seeds (RRYY) and Wrinkled Green seeds (rryy).
  2. F1 generation, all plants having round yellow seeds (RrYy) were obtained.
  3. Self-pollination of plants of F1 generation.
  4. F2 generation (16 plants were obtained) Phenotypic Ratio- 9:3:3:1 [9 had round yellow seeds (RrYy), 3 had round green seeds (Rryy), 3 had wrinkled yellow seeds (rrYy), and 1 had wrinkled green seeds (rryy)]. Genotypic Ratio (Nine genotypes were obtained)– 1:2:2:4:1:2:1:2:1

PSEB Solutions Class 10 Biology Chapter 3 Mendel's Experiments Dihybrid Cross

Simple Trick To Learn Genotypic Ratio In Dihybrid Cross

  1. Remember that there will be 9 genotypes in dihybrid cross.
  2. Now write the first gene combination 3 times each, i.e., RR, Rr and rr need to be written three times each.
  3. Write the other gene combination only once, i.e., YY, Yy and yy, and then repeat this three times.
  4. Write ratio as 1:2:1 from top, and 1:2:1 from bottom.
  5. In the middle three rows double the ratios written in the first three rows. This will give the genotypic ratio in dihybrid cross (1:2:1:2:4:2:1:2:1).

These steps are shown below:

PSEB Solutions Class 10 Biology Chapter 3 Learn Genotypic Ratio In Dihybrid Cross

Mendel’s Laws Of Inheritance

  1. Law Of Dominance – If the set of alleles comes from parent (male and female) to offspring then, the dominant allele is expressed and the recessive allele has no noticeable effect.
  2. Law Of Segregation – The two alleles for a character separate during gamete formation (notice separation of alleles in FI and F2 generation of monohybrid and dihybrid cross).
  3. Law Of Independent Assortment or Inheritance – The two pair of alleles are inherited independently of each other.

Some Important Terms

  1. DNA- It is the information source for making proteins in the cell.
  2. Gene- A section of DNA that provides information for one protein is called the gene for that protein. Characteristics or traits of an organism are controlled by genes.
  3. Allele- An allele is one of two or more versions of a gene. e.g. TT, tt, Tt. An individual inherits two alleles for each gene, one from each parent.
  4. Homozygous- It means that the organism has two copies of the same allele for a gene. e.g. TT, tt.
  5. Heterozygous- It means that the organism has two different alleles of a gene. e.g. Tt.
  6. Phenotype- The trait which is visible in an organism is called its phenotype, e.g. Phenotypic ratio in F2 generation of monohybrid cross is 3:1.
  7. Genotype- The actual composition of genes present in an organism is called its genotype, e.g. Genotypic ratio in F2 generation of monohybrid cross is 1:2:1.

Sex Determination- The process of determining the biological sex of an offspring before its birth. Different strategies are used by different species for sex determination such as environmental factors and genetics.

Summary Of Sex Determination Methods In Different Species

PSEB Solutions Class 10 Biology Chapter 3 Sex Determination Methods In Different Species

Sex Determination In Humans – Genetic Factors

  1. In human, sex of the offsprings is largely genetically determinied, and father is resp[onsible for the sex of the offspring.
  2. Humans have 23 pairs of chromosomes – 22 pairs of XX chromosomes (one X in each pair comes from mother and the other X comes from father) + 1 pair of sex chromosome (women have XX, while men have XY).
  3. During gamets formation, separation of chromosomes takes place. therefore, males produce two types of sperms X and Y, while female produces one type of egg X.
  4. If a X type of sperm fertilizes the egg then offspring will be female (XX). If Y type of sperm fertilizes the egg then offspring will be male (XY). Thus, the sex of the offspring will be determined by what they inherit from their father.

PSEB Solutions Class 10 Biology Chapter 3 Sex Determination In Humans Genetic Factors

Chapter 3 Heredity And Evolution Reason-Assertion Questions And Answers

For question provided below, two statements are given—one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

  1. Both A and R are true, and R is the correct explanation of the assertion.
  2. Both A and R are true, but R is not the correct explanation of the assertion.
  3. A is true, but R is false.
  4. A is false, but R is true.

Question 1. Assertion: Mendel chose pea plant for his experiments.

Reason: Pea plant provides diverse visible traits and has a short life span.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 2. Assertion: When TT and tt pea plant were crossed, only tall plants were obtained in FI progeny.

Reason: This was because tall allele was dominant over the short allele.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 3. Assertion: A geneticist crossed a pea plant having violet flowers with a pea plant with white flowers, he got all violet flowers in first generation.

Reason: White colour gene is not passed on to next generation.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 4. Assertion: Acquired trait cannot be passed on from one generation to next generation.

Reason: Acquired trait cannot change the DNA of the germ cells.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 5. Assertion: In some reptiles, the temperature at which fertilised egg is incubated before hatching plays a role in determining sex of offspring.

Reason: In turtle, high incubation temperature above 33°C leads to development of female offspring whereas in lizards high incubation temperature results in male offspring.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 6. Assertion (A): If mother has two dominant alleles for black hair and father has two recessive alleles for blonde hair then their child will inherit one dominant allele from mother and one recessive allele from father and will have black hair.

Reason (R): Progeny inherits one genes for each trait from its parents but the trait shown by progeny depends on inherited alleles.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 7. Assertion (A): Genes present in every cell of an organism control the traits of the organisms.

Reason (R): Gene is specific segment of DNA occupying specific position on a chromosome.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 8. Assertion (A): A child which has inherited X chromosome from father will develop into a girl child.

Reason (R): Girl child inherits X chromosome from father and Y chromosome from mother.

Answer: 3. A is true, but R is false.

Question 9. Assertion (A): In human males all the chromosomes are perfectly paired except X and Y chromosomes.

Reason (R): X and Y are sex chromosomes.

Answer: 1. Both A and R are true, and R is the correct explanation of the assertion.

Question 10. Assertion (A): A heterozygous tall plant when crossed with homozygous dwarf plant will produce tall and dwarf plants in the ratio of 3:1.

Reason (R): A heterozygous tall plant will produce two types of gametes, i.e., one with T and other with t whereas homozygous dwarf plant produce all gametes with t only.

Answer: 4. A is false, but R is true.

Question 11. Assertion (A): Selfing of a plant for several generations helps plant breeders to obtain pure breeding varieties.

Reason (R): Pure breeding plants are heterozygous for many traits.

Answer: 3. A is true, but R is false.

Question 12. Assertion (A): In humans, height is a trait which shows variation.

Reason (R): Some humans are very tall, some have medium height whereas others are short heighted.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Question 13. Assertion (A): Evolution is an extremely slow process.

Reason (R): New characters are accumulated in an organism during its lifetime.

Answer: 3. A is true, but R is false.

Question 14. Assertion (A): Mutation is sudden change in the genetic material.

Reason (R): Variation is useful for the survival of species over time.

Answer: 2. Both A and R are true, but R is not the correct explanation of the assertion.

Chapter 3 Heredity And Evolution Case Or Source Based Questions

Question 1. Mendel proposed two general rules to consolidate his understanding of inheritance in monohybrid crosses. These are called the Principles or Laws of Inheritance: the First Law or Law of Dominance and the Second Law or Law of Segregation. The Law of Dominance is used to explain the expression of only one of the parental characters in a monohybrid cross in the FI and the expression of both in the F2.

It also explains the proportion of 3:1 obtained at the F2. The Law of Segregation is based on the fact that the alleles do not show any blending and that both the characters are recovered as such in the F2 generation though one of these is not seen at the FI stage. Though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors. A homozygous parent produces all gametes that are similar while a heterozygous one produces two kinds of gametes each having one allele with equal proportion.

1. In a dihybrid cross, pure homozygous plants will be

  1. 9
  2. 2
  3. 1
  4. 3

Answer: 2. 2

2. Mendel observed red flowers in FI generation, when he crossed red and white because of

  1. Dominance
  2. Recessive gene
  3. Law of independent assortment
  4. Law of segregation

Answer: 1. Dominance

3. The blood group containing anti A and anti B is

  1. Blood group A
  2. Blood group B
  3. Blood group AB
  4. Blood group O

Answer: 4. Blood group O

4. A typical genotypic monohybrid ratio is

  1. 9:3:3:1
  2. 1:2:1
  3. 3:1
  4. 9:7

Answer: 2. 1:2:1

5. Independent assortment of Mendel was proved by

  1. Monohybrid cross
  2. Dihybrid cross
  3. Incomplete dominance
  4. Back cross

Answer: 2. Dihybrid cross

Question 2. Pure bred pea plant with smooth seeds (dominated characteristic) were crossed with purebred pea plant with wrinkled seeds (recessive characteristic). The FI generation was self-pollinated to give rise to the F2 generation.

What will be the genotypic ratio of the given F2 generation?

If a genotype consists of different types of alleles, what is it called?

What is the alternative form of the gene?

Answer:

  1. In given case, genotypic ratio of F2 progeny will be 1:2:1 where, one is homozygous dominant, two are heterozygous dominant and one is homozygous recessive,
  2. Alleles
  3. Allele

Question 3. Mendel experimented on a pea plant and considered 7 main contrasting traits in the plants. In monohybrid experiment, Mendel took two pea plants of opposite traits (one short and one tall) and crossed them. He found the first generation offspring were tall and called it FI progeny. Then he crossed FI progeny and obtained both tall and short plants in the ratio 3:1.

In a dihybrid cross experiment, Mendel considered two traits, each having two alleles. He crossed wrinkled-green seed and round-yellow seeds and observed that all the first generation progeny (FI progeny) were round-yellow. This meant that dominant traits were the round shape and yellow colour. He then self-pollinated the FI progeny and obtained 4 different traits wrinkled-yellow, round-yellow, wrinkled-green seeds and round-green in the ratio 9:3:3:1.

1. Which of the following was not a trait considered by Mendel for his experiments?

  1. Flower colour
  2. Pod shape
  3. Stem height
  4. Seed type

Answer: 4. Seed type

2. What is the phenotypic ratio of the F2 progeny in a dihybrid cross?

  1. 3:1
  2. 1:2:1
  3. 9:3:3:1
  4. 3:4

Answer: 3. 9:3:3:1

3. What is the genotypic ratio of the F2 progeny in a monohybrid cross?

  1. 3:1
  2. 1:2:1
  3. 9:3:3:1
  4. 3:4

Answer: 3. 9:3:3:1

4. A cross between tall and dwarf plants will produce which type of plants in the F1 generation?

  1. Tall
  2. Dwarf
  3. Semi-dwarf
  4. Short

Answer: 1. Tall

5. Because of his contribution to the field of genetics, Mendel is known as the

  1. Father of genetics
  2. Father of botany
  3. Father of medicine
  4. Father of plant physiology

Answer: 1. Father of genetics

Question 4. In human, the allele for brown eyes (B) is dominant over that for blue eyes (b). A brown-eyed woman marries a blue-eyed man, and they have six children. Four of the children are brown-eyed and two of them are blue-eyed.

  1. What is the genotype of blue-eyed offspring?
  2. What is the woman’s genotype?
  3. What is the gene carried by the mother’s ovum regarding the eye colour?
  4. What is the gene carried by the man’s sperm regarding the eye color?

Answer:

  1. bb
  2. Bb According to the given passage some children show recessive trait, i.e., homozygous. So, the woman must be heterozygous.
  3. B or b Human ova are haploid, hence they only contain one copy of each gene. Since the woman has a Bb genotype her ova would contain either B or b allele.
  4. Human sperm is haploid, hence they only contain one copy of each gene. Since the man has a bb genotype, his sperm would contain allele b only.

Question 5. Mendel conducted dihybrid cross which involved two pairs of contrasting characters. The results obtained were amazingly unique. Mendel is known as the Father of Genetics.

PSEB Solutions Class 10 Biology Chapter 3 Mendel Conducted Dihybrid Cross Which Involved Two Pairs Of Contrasting Characters

1. Which two pairs of contrasting characters are involved in the above parental cross?

  1. Round, yellow and green wrinkled
  2. Round green and yellow wrinkled
  3. Wrinkled yellow and round green
  4. Flat yellow and constricted green

Answer: 1. Round, yellow and green wrinkled

2. What is the genotype of the parent with round and wrinkled seeds?

  1. RRYY
  2. RRyy
  3. RrYy
  4. rrYY

Answer: 2. RRyy

3. In the FI generation, what is the phenotype of the offspring?

  1. Round and yellow
  2. Green and round
  3. Green and wrinkled
  4. Round and wrinkled

Answer: 1. Round and yellow

4. How many heterozygous offspring are produced in the F2 generation, if a total of 16 offspring are produced?

  1. 12
  2. 14
  3. 16
  4. 4

Answer: 2. 14

5. What is the ratio of parental combination to recombinants?

  1. 1:7
  2. 3:4
  3. 1:3
  4. 3:1

Answer: 1. 1:7

Question 6. Peter Norman, a leading UK podiatrist who has been treating the Royal Ballet for 16 years, has seen a lot in his days. He says it’s common for dancers to tape their feet simply and go on pointe with broken toes or stress fractures. He says it’s due to the pressure and insecurity of their jobs. People push their limits to keep their position. The constant pressure on the tip of their toes and the quick bursts of jumping in the air and landing perfectly, the stretching of their tendons and feet fit into impossible shaped shoes has altered the shape of their feet. But for a lot of dancers, this has become a part of them and a part of how they survive these shoes. Most of them won’t allow their doctors to remove the thickened skin at their toe-heads because that is how they survive the shoes. Norman claims he has seen patients whose feet require at least a few weeks to a month’s rest, but they refuse to take more than a night. Among men, it’s different for they wear soft canvas shoes. There’s a lot of jumping and lifting women involved and that results in ankle and tendon injuries.

PSEB Solutions Class 10 Biology Chapter 3 Ankle And Tendon Injuries

  1. Why do you think ballerinas are made to do this to their toes?
  2. Do you think these injuries will make any changes in their DNA Or genes?
  3. Will their offspring be born with such feet?
  4. Is it an acquired or inherited trait?

Answer:

  1. There’s a lot of jumping and lifting women involved and that results in ankle and tendon injuries. However, due to the pressure and insecurity of their jobs, they refuse to take proper treatment and rest and push their limits to keep their position.
  2. No.
  3.  No, because this is not an inherited trait.
  4. Acquired trait.

Question 7. Haemophilia is an X-linked disorder characterized by the inability to properly form blood clots. Until recently, haemophilia was untreatable, and only a few haemophiliacs survived to reproductive age because any small cut or internal haemorrhaging after even a minor bruise were fatal. Now haemophilia is treated with blood transfusions and infusions of a blood derived substance known as antihemophilic factor. However, the treatment is very expensive and occasional problems can arise because of a patient’s allergic reactions or other transfer complications. Haemophilia affects males much more frequently (1 in 10,000) than females (1 in 100,000,000). This occurs because a critical blood clotting gene is carried on the X chromosome. Since males only carry one X chromosome, if that is defective, haemophilia will immediately show up. An early death is likely. Females, on the other hand, carry two X chromosomes. If only one is defective, the other normal X chromosome can compensate. The woman will have normal blood clotting; she will simply be a carrier of the recessive defective gene. This fact will be discovered if some of her children are haemophiliacs. Naturally, women haemophiliacs are rare because it takes two defective X chromosomes in order for the condition to be seen.

PBSE Solutions Class 10 Biology Chapter 3 Haemophilia Is An X-Linked Disorder Characterized By The Inability To Properly Form Blood Clots

 

  1. What are the problems associated with haemophilia?
  2. How does this disease gets transferred?
  3. Do you think these will make any changes in the DNA/ genes?
  4. Can the offspring be born with such a disease? Does the female have more chances to get the disease or the male?
  5. Is it an acquired or inherited trait?

Answer:

  1. Inability to properly form blood clots.
  2. Since the blood clotting gene is carried on the X chromosome, t gets transferred from parents to offsprings through chromosomes.
  3. Yes. Blood clotting gene is carried on the X chromosome. Since males only carry one X chromosome, if that is defective, haemophilia will immediately show up. An early death is likely. Females, on the other hand, carry two X chromosomes. If only one is defective, the other normal X chromosome can compensate. The woman will have normal blood clotting; she will simply be a carrier of the recessive defective gene. This fact will be discovered if some of her children are haemophiliacs.
  4. Yes, the offspring can be born with such a disease. Blood clotting gene is carried on the X chromosome. Males have more chances to get the disease since males only carry one X chromosome, if that is defective, haemophilia will immediately show up. An early death is likely. Females, on the other hand, carry two X chromosomes. If only one is defective, the other normal X chromosome can compensate. The woman will have normal blood clotting; she will simply be a carrier of the recessive defective gene. This fact will be discovered if some of her children are haemophiliacs.
  5. Inherited trait.

 

PSEB Class 10 Physics Solutions For Chapter 4 Magnetic Effects Of Current

PSEB Class 10 Biology Solutions For Chapter 4 Magnetic Effects Of Current

Background

Hans Christian Oersted discovered that electricity and magnetism are interrelated forces. Einstein’s “Theory Of Relativity” later proved that electricity are magnetism are two different aspects of one common phenomenon.

However, in practical terms, electric and magnetic forces behave quite differently – although electric forces are produced by electric charges either at rest or in motion, magnetic forces are produced only by moving charges, and act solely on charges in motion.

Magnet

A substance which can attract a piece of iron, cobalt, or nickel is called a magnet. The property by virtue of which a magnet attracts these substances is called magnetism. A magnet has two poles, viz. North Pole and South Pole as shown:

PSEB Class 10 Biology Solutions For Magnet

Magnetic Field

The region around a magnet where the effect of a magnet can be felt is called magnetic field. Magnetic field is a vector quantity, i.e., magnetic field has both direction and magnitude. It is created by an electric current or magnetic dipole.

Magnetic Field Lines

The lines along which the iron filings align themselves, when a bar magnet is brought near them, are called magnetic field lines.

Magnetic field lines are imaginary lines to visualize magnetic field, For Example. When we bring a bar magnet near iron filings, the iron fillings arrange themselves in a pattern as shown. This pattern of lines indicates the magnetic field lines around the bar magnet.

PSEB Class 10 Biology Solutions For Magnetic Field Lines

Electromagnetism

The branch of physics that studies the interactions between electric and magnetic fields is called electromagnetism.

Sign Conventions About Magnetic Field Lines

  1. Magnetic field lines always begin from the N-pole of a magnet and end on the S-pole of the magnet.
  2. Magnetic field lines form closed curves, i.e, inside the magnet they move from South pole to North pole.
  3. Magnetic field lines never cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.
  4. The strength of magnetic field is indicated bv the degree of closeness of the field lines. So, magnetic field is the strongest, where the field lines are closest together.

Factors On Which Magnetic Field Depends – Two factors determining amount of magnetic field (B) produced by a current carrying conductor are:

Magnetic field produced is directly proportional to current (I), i.e., B ∝ I

Magnetic field produced is inversely proportional to the radius (r) of the circular loop, i.e, B ∝ 1/r

PSEB Class 10 Physics Solutions Chapter 4

Right Hand Thumb Rule Or Maxwell’s Corkscrew Rule – It gives the direction of magnetic field lines in a current carrying conductor.

According to this rule, if we grasp (or hold) the current-carrying wire in our right hand so that our thumb points in the direction of current, then the direction in which our fingers encircle the wire will give the direction of magnetic field lines around the wire. This is shown in figure below:

 

PSEB Class 10 Biology Solutions For Right Hand Thumb Or Maxwell's Corkscrew Rule

From the above figure, one can easily deduce that if the direction of current in a conductor is reversed, the direction of magnetic field lines will also get reversed.

Maxwell’s Corkscrew Rule

If we consider ourselves driving a corkscrew in the direction of the current, then the direction of the rotation of the corkscrew is the direction of the magnetic field.

Magnetic Field Produced Due To Flow Of Current In A Straight Wire, A Circular Loop, And A Solenoid

1. Magnetic field due to a current through a straight wire – The amount of magnetic field produced is proportional to the current in the conductor. The direction of the current can be found using right-hand thumb rule.

2. Magnetic field due to a current through a circular loop – We know that the magnetic field produced by a current-carrying straight wire depends inversely on the distance (r) from it.

Therefore, the concentric circles representing the magnetic field around it would become larger and larger as we move away from the wire as shown in the figure.

Further, on reaching the centre of the circular loop, the arcs of these big circles will become almost straight and therefore, would appear as straight lines as shown in figure:

PSEB Class 10 Biology Solutions For Magnetic Field Due To A Current Through A Straight Wire

By applying the right hand thumb rule on the above current carrying wire, we can observe the following:

  • Every section of the wire contributes to the magnetic field lines in the same direction within the loop.
  • Direction of magnetic field at the centre of circular coil is perpendicular to the plane of the coil, i.e., along the axis of the coil.

3. Magnetic field due to solenoid – A solenoid is a long cylindrical coil of insulated copper wire having large number of circular turns as shown in figure:

PSEB Class 10 Biology Solutions For Magnetic Field Due To Solenoid

A current carrying solenoid is called an electromagnet because when current is passed through a solenoid, magnetic field is created.

Magnetic field produced by a solenoid is similar to the magnetic field produced by a bar magnet. Due to the presence of turns in the solenoid, magnetic field inside the solenoid is in the form of parallel straight lines, and is the same at all points inside the solenoid as shown in figure.

PSEB Class 10 Biology Solutions For Magnetic Field Inside The Solenoid

Strength of magnetic field produced by a current carrying solenoid depends on following factors:

  1. Number Of Turns In The Solenoid – Larger the number of turns in the solenoid, greater will be the magnetism produced.
  2. Strength Of Current In The Solenoid– Larger the current passed through solenoid, stronger will be the magnetic field produced.
  3. Nature of the core material – The use of soft iron rod as core in a solenoid produces the strongest magnetism.

Advantages of electromagnets (current carrying solenoid) over bar magnets

  1. Unlike bar magnets, electromagnets can be switched on and switched off.
  2. Magnetic field inside electromagnets can be increased by increasing the number of turns in the coil.

Force on a current carrying conductor in a magnetic field – So far we know that a current-carrying conductor produces a magnetic field around it, i.e, it behaves like a magnet and exerts a force when a magnet is placed in its magnetic field.

In addition to this, the magnetic field also exerts equal and opposite force on the currentcarrying conductor because when the two magnetic fields (i.e., magnetic field produced by the current-carrying conductor and magnetic field due to the nearby magnet) interact with eachother.

There exist attractive or repulsive forces between the two magnetic fields depending upon the direction of the external magnetic field and the direction of the current in the conductor.

The direction of force acting on the current carrying conductor can be determined using Fleming’s Left-Hand Rule.

According to Fleming’s Left Hand Rule, if the left hand is stretched in a way that the forefinger, the center finger, and the thumb are in mutually perpendicular directions.

Then the direction of the forefinger will give the direction of magnetic field, the direction of center finger will give the direction of electric current and the direction of thumb will give the direction of force acting on the conductor as shown:

PSEB Class 10 Biology Solutions For Fleming's Left-Hand Rule

Factors Affecting Direction Of Force In A Current Carrying Conductor

  1. Direction of Current – If we change the direction of flow of current, the direction of force will change.
  2. Direction of Magnetic Field– If we change the direction of poles of magnet, the direction of force will change.

Magnetic Effects Of Current PSEB Class 10 Notes

Factors Affecting Magnitude Of Force In A Current Carrying Conductor

  1. Amount of current flowing through the conductor – More the amount of current flowing through the conductor, more will be the force.
  2. Direction of Magnetic Field – Force acting on a current carrying conductor is highest when the direction of magnetic field is perpendicular to the direction of electric current.

Applications Of Magnetism In Real Life

  1. MRI (Medical Resonance Imaging).
  2. Magnetic Compass is used during hiking for finding the direction as it always points towards North-South direction.
  3. Electric Motors – An electric motor is a rotating device that converts electrical energy to mechanical energy. Electric motors are used in hair dryers, electric razors, hair and beard trimmers, washing machines, etc.
  4. An electric motor works on the principle of magnetic effects of current. An electric motor consists of a rectangular coil placed in a magnetic field. When current is passed through the coil, the coil rotates as a result of the forces acting on it.

Electromagnetic Induction – It is the process of using magnetic fields to produce voltage or current in a closed circuit.

Points To Remember About Electromagnetic Induction

  1. Electromagnetic Induction was discovered by Michael Faraday.
  2. Electromagnetic induction is a way of producing electrical current in a circuit by using only the force of a magnetic field, and not batteries.
  3. Transformers and Generators work on the principle of electromagnetic induction.

Factors Affecting Electromagnetic Induction

  1. Number of turns of wire in the coil – More the number of turns in the coil, more will be the voltage or current produced.
  2. Increasing the speed of the relative motion between the coil and the magnet will increase the voltage or current produced.
  3. Increasing the strength of the magnetic field – If the same coil of wire is moved at the same speed through a stronger magnetic field, more voltage or current will be produced.

Electric Generator – An electric generator, also called a dynamo, is a machine that converts mechanical energy into electricity for transmission and distribution over power lines.

Working Of An Electric Generator

PSEB Class 10 Biology Solutions For Working Of An Electric Generator

An electric generator works on the principle of electromagnetic induction.

  1. In an electric generator, a conductor coil, called armature (a copper coil tightly wound onto a metal core), connected to a shaft of a mechanical energy source (such as a motor) is rotated rapidly between the poles of a horseshoe-type magnet.
  2. The energy to the mechanical energy source is provided by engines operating on fuels such as diesel, petrol, etc.

Fleming’s Right Hand Rule (For Generators)- It gives the direction of induced current when a conductor attached to a circuit moves in a magnetic field.

According to Fleming’s Right Hand Rule, if the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of the conductor, then the middle finger will show the direction of the induced current.

PSEB Class 10 Biology Solutions For Fleming's Right Hand Rule

Please Note:

  1. Fleming’s left-hand rule is used for electric motors, while Fleming’s right-hand rule is used for electric generators.
  2. In other words, Fleming’s left hand rule should be used if one were to create motion, while Fleming’s right hand rule should be used if one were to create electricity.

Alternating Current (AC) And Direct Current (DC)

Electric current flows in two ways – Alternating Current (AC) and Direct Current (DC). These are shown graphically in figure below:

PSEB Class 10 Biology Solutions For Alternating Current (Ac) And Direct Current (DC)

Difference Between Alternating Current (AC) And Direct Current (DC)

PSEB Class 10 Biology Solutions For Difference Between Alternating Current (AC) And Direct Current (DC)

Advantages Of Alternating Current (AC) Over Direct Current (DC)

  1. DC current is normally available from a source like a battery. We cannot have large enough batteries to supply all our needs.
  2. Electricity needs to be generated continuously to fulfil our needs. In AC, electricity is generated by the rotation of a coil in a magnetic field, whereas a DC generator requires brushes to convert the AC to DC within the machine. Thus, DC requires additional effort and energy.
  3. Once electricity is generated, it needs to be transmitted over long distances. The transmission is more economical in AC
  4. Coming to the last stage i.e. usage, though most of the consumers use electricity for lighting in which case AC or DC does not make a difference (that also depends based on the lighting device) the major demand of electricity is for mechanical power. That conversion (electrical to mechanical) is more easily and economically done by AC motor for similar reasons as an AC generator.

Due to the above reasons, use of AC is advantageous over DC.

Disadvantages of Alternating Current (AC) Over Direct Current (DC) – AC cannot be stored.

Domestic Electric Circuits) – Domestic electric circuits use three kinds of wires-

  1. Live wire (positive) with red insulation cover.
  2. Neutral wire (negative) with black insulation cover.
  3. Earth wire with green insulation cover. Earth wire protects us from electric shock in case of leakage of current, especially in metallic appliances, by providing a low resistance path for flow of current in case of leakage.

The flow of current in the domestic circuit follows the following path (as shown in figure below):

PSEB Class 10 Physics Important Questions Chapter 4

Pole → Main Supply → Fuse → Electricity Meter → Distribution Box → To Separate Circuits

PSEB Class 10 Biology Solutions For Domestic Electric Circuits

Note: The potential difference between Live wire and Neutral wire in India is 220V.

Short Circuit – Short circuit occurs when live wire accidentally comes in contact with neutral wire. Short circuit can occur due to following reasons:

  1. Faulty Wire Insulation – If the insulation of wires is damaged, live wire may come in contact with a neutral wire, causing short circuit.
  2. Damaged Or Loose Wire Connections – This may lead to overheating of the wires resulting in damage to the insulating coating of the wire, and hence short circuit.

Safety Devices To Prevent Short Circuit– Electric Fuse, Earth wire, MCB (Miniature Circuit Breaker).

Overloading– When current drawn is more than current carrying capacity of a conductor, it results in overloading.

Causes Of Overloading

  1. Accidental hike in voltage supply.
  2. Use of more than one device in a single socket.

Chapter 4 Magnetic Effects Of Current Reason- Assertion Questions And Answers

The following questions consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below:

  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false but R is true.

Question 1. Assertion (A): On changing the direction of flow of current through a straight conductor, the direction of a magnetic field around the conductor is reversed.

Reason (R): The direction of magnetic field around a conductor can be given in accordance with left hand thumb rule.

Answer: 3. A is true but R is false.

Question 2. Assertion (A): The magnitude of the magnetic field at a point on the axis of a current carrying solenoid is inversely proportional to the current flowing through the solenoid.

Reason (R): The magnitude of the magnetic field at a point on the axis of a current carrying solenoid is directly proportional to the number of turns per unit length of a solenoid.

Answer: 4. A is false but R is true.

Question 3. Assertion (A): A compass needle is placed near a current-carrying wire. The deflection of the compass needle decreases when the magnitude of an electric current in the wire is increased.

Reason (R): Strength of a magnetic field at a point near the conductor increases on increasing the current.

Answer: 4. A is false but R is true.

Question 4. Assertion (A): The strength of the magnetic field produced at the centre of a current carrying circular coil increases on increasing the radius of the circular coil.

Reason (R): Magnetic field strength is inversely proportional to the radius of the circular coil.

Answer: 4. A is false but R is true.

Question 5. Assertion (A): Alternating Current is used in household supply.

Reason (R): AC electric power can be transmitted over long distances without much loss of energy.

Answer: 1. Both A and R are true and R is the correct explanation of A.

Question 6. Assertion (A): A current carrying wire deflects a magnetic needle placed near it.

Reason (R): A magnetic field exists around a current carrying wire.

Answer: 1. Both A and R are true and R is the correct explanation of A.

PSEB Class 10 Science Chapter 4 Solutions

Chapter 4 Magnetic Effects Of Current Case Or Source-Based Questions And Answers

Question 1.

A solenoid is a long helical coil of wire through which a current is run in order to create a magnetic field. The magnetic field of the solenoid is the superposition of the fields due to the current through each coil. It is nearly uniform inside the solenoid and close to zero outside, and is similar to the field of a bar magnet having a north pole at one end and a south pole at the other, depending upon the direction of current flow. The magnetic field produced in the solenoid is dependent on a few factors such as the current in the coil, the number of turns per unit length, etc. The following graph is obtained by a researcher while doing an experiment to see the variation of the magnetic field with respect to the current in the solenoid. The unit of magnetic field as given in the graph attached is in milli-Tesla (mT) and the current is given in Ampere.

PSEB Class 10 Biology Solutions For The unit Of Magnetic Field As given In The Graph Attached Is Milli-Tesla

1) What type of energy conversion is observed in a linear solenoid?

  1. Mechanical to Magnetic
  2. Electrical to Magnetic
  3. Electrical to Mechanical
  4. Magnetic to Mechanical

Answer: 3. Electrical to Mechanical

2) What will happen if a soft iron bar is placed inside the solenoid?

  1. The bar will be electrocuted, resulting in a short circuit.
  2. The bar will be magnetised as long as there is current in the circuit.
  3. The bar will be magnetised permanently.
  4. The bar will not be affected by any means.

Answer: 2. The bar will be magnetised as long as there is current in the circuit.

3) The magnetic field lines produced inside the solenoid are similar to those of ______

  1. A bar magnet
  2. A straight current-carrying conductor
  3. A circular current-carrying loop
  4. Electromagnet of any shape

Answer: 1. A bar magnet

4) After analysing the graph, a student writes the following statements.

  • The magnetic field produced by the solenoid is inversely proportional to the current.
  • The magnetic field produced by the solenoid is directly proportional to the current.
  • The magnetic field produced by the solenoid is directly proportional to the square of the current.
  • The magnetic field produced by the solenoid is independent of the current.

Choose from the following which of the following would be the correct statement(s).

  1. Only IV
  2. I and III and IV
  3. I and II
  4. Only II

Answer: 4. Only II

5) From the graph, deduce which of the following statements is correct.

  1. For a current of 0.8 A, the magnetic field is 13 mT
  2. For larger currents, the magnetic field increases non-linearly.
  3. For a current of 0.8 A, the magnetic field is 1.3 mT
  4. There is not enough information to find the magnetic field corresponding to 0.8A current.

Answer: 1. For a current of 0.8 A, the magnetic field is 13 mT

Question 2. Ruchi fixes a sheet of white cardboard on a drawing board. She places a bar magnet in the centre of it. She sprinkles iron filings uniformly around the bar magnet. Then she taps the board gently and observes that the iron fillings arrange themselves in a particular pattern.

1) What does the pattern shape look like?

  1. Straight lines
  2. Squares
  3. Closed curves
  4. Parallel lines

Answer: 3. Closed curves

2) Why do iron filings arrange in a pattern?

  1. Due to the poles of a magnet
  2. Due to the force exerted by the magnet within its magnetic field
  3. Due to repulsion between the poles and filings
  4. None of the above

Answer: 2. Due to force exerted by the magnet within its magnetic field

3) What do the lines along which iron filings align represent?

  1. Magnetic field lines
  2. Magnetic force
  3. Magnetic induction
  4. Magnetic susceptibility

Answer: 1. Magnetic field lines

PSEB Class 10 Science Chapter 4 Solutions

4) What does the crowding of iron filings at the end of the magnet indicate?

  1. The magnetic field is weak at the poles and stronger in the middle
  2. The magnetic field is stronger at the poles and weaker at the middle
  3. Magnetic field strength goes on decreasing from the north to the south pole
  4. Magnetic field strength goes on decreasing from the south to the north pole

Answer: 2. The Magnetic field is stronger at the poles and weaker at the middle

5) How is the strength of the magnetic field is indicated?

  1. Magnetic field strength cannot be indicated by magnetic field lines
  2. Far the magnetic field lines, more is the magnetic strength
  3. The closer the magnetic field lines are the magnetic field strength
  4. The closer the magnetic field lines, more is the magnetic strength

Answer: 4. Closer the magnetic field lines, more is the magnetic strength

Question 3. The magnetic field at any point is the combined effect of the magnetic field due to the current in the wire and the magnetic field of the Earth. Iron filings, when placed near the wire carrying current, are arranged in circles due to the magnetic field produced by the current flowing through the wire. However, at a point far away from the wire, the magnetic field due to the Earth is predominant as compared to the magnetic field due to the current, due to which the iron filings are arranged in straight lines. The point where the two fields are equal and opposite is called the neutral point. At the neutral point, the net magnetic field is zero, and the compass needle at this point rests in any direction.

1) How are the magnetic field lines at the point near the straight current-carrying conductor?

  1. A concentric circles pattern whose centre lies on a wire
  2. Uniform and parallel line pattern
  3. Spiral pattern
  4. Zig-zag pattern

Answer: 1. Concentric circles pattern whose centre lies on the wire

2) To what parameter is the magnitude of the magnetic field produced by the straight conductor directly proportional?

  1. Distance from the conductor
  2. Strength of current in wire
  3. External forces acting on the wire
  4. Nature of material

Answer: 2. Strength of current in wire

3) Which rule is used to find the direction of the magnetic field produced by the straight current-carrying conductor?

  1. Maxwell’s left-hand thumb rule
  2. Maxwell’s right-hand thumb rule
  3. Fleming’s left-hand rule
  4. Fleming’s right-hand rule

Answer: 2. Maxwell’s right-hand thumb rule

4) What, according to the rule, will be the direction of the current when lines of the magnetic field are in the anti-clockwise direction?

  1. Downward direction
  2. Left direction
  3. Upward direction
  4. Right direction

Answer: 3. Upward direction

5) SI unit of magnetic field is

  1. Gauss
  2. Coulomb
  3. Weber
  4. Tesla

Answer: 4. Tesla

Question 4. The magnetic field at any point is the combined effect of the magnetic field due to the current in the wire and the magnetic field of the Earth. Iron filings, when placed near the wire carrying current, are arranged in circles due to the magnetic field produced by the current flowing through the wire. However, at a point far away from the wire, the magnetic field due to the Earth is predominant as compared to the magnetic field due to the current due to which the iron filings are arranged in straight lines. The point where the two fields are equal and opposite is called the neutral point. At the neutral point, the net magnetic field is zero and the compass needle at this point rests in any direction.

  1. How are the magnetic field lines at the point near the straight current-carrying conductor?
  2. To what parameter is the magnitude of the magnetic field produced by the straight conductor directly proportional?
  3. Which rule is used to find the direction of the magnetic field produced by the straight current-carrying conductor?

Answer:

  1. The magnetic field lines around the straight conductor carrying current are concentric circles whose centre lies on the wire.
  2. The magnitude of the magnetic field is directly proportional to the current passing through the wire,
  3. Maxwell’s right-hand thumb rule is used to find the direction of the magnetic field produced by a straight current-carrying conductor.

Question 5. Andre Marie Ampere suggested that a magnet must exert an equal and opposite force on a current-carrying conductor, which was experimentally found to be true. But we know that current is due to charges in motion. Thus, it is clear that a charge moving in a magnetic field experiences a force, except when it is moving in a direction parallel to it. If the direction of motion is perpendicular to the direction of magnetic field, the magnitude of force experienced depends on the charge, velocity (v), strength of the magnetic field (B), and sine of the angle between v and B. The Direction of magnetic force is given by Fleming’s left-hand rule.

PSEB Class 10 Biology Solutions For Direction Of Magnetic Force Is Given By Fleming's Left Hand Rule

1. If an electron is travelling horizontally towards east. A magnetic field in vertically downward direction exerts a force on the electron along which direction?

2. If a charged particle is moving along a magnetic field line, what would be the magnetic force on the particle?

3. A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure. In the field, an electron and a proton move as shown. Where do the electron and the proton experience the force?

PSEB Class 10 Biology Solutions For A Uniform Magnetic Field Exists In The plane Of Paper From Left to Right

Answer:

  1. Fleming’s left hand rule is used to determine the direction of force on electron i.e., in south direction.
  2. The angle between velocity and magnetic field is zero. Therefore, magnetic force on the particle is zero.
  3. As the direction of current is taken opposite to the direction of motion of electrons, therefore, current from the motion of electron and proton is in the same direction, i.e., from bottom to top. Now, according to Fleming’s left hand rule, the electron and the proton experience forces both pointing into the plane of paper.

Question 6. A current-carrying wire produces a magnetic field around it. The phenomenon in which an electromotive force and current (if the conductor is in the form of a closed circuit) is induced by changing a magnetic field (or by passing magnetic field lines) through it is called electromagnetic induction. The emf so developed is called induced emf and the current made to flow is called induced current.

PSEB Class 10 Biology Solutions For A Current Carrying Wire Produces Magnetic Field Around It

The cause of induced emf was discovered by Faraday and Flenry. It can be concluded that the induced current flows in a conductor as long as the magnetic lines of force change within the conductor. In case of relative motion i.e., motion of coil w.r.t to magnet or vice versa, the direction of the current flowing in the conductor is determined by the direction of the relative motion of the conductor with respect to the magnetic field. The induced emf or current is directly proportional to the rate of change in magnetic field.

1. A student connects a coil of wire with a sensitive galvanometer as shown in the figure. Where will he observe the deflection in the galvanometer of bar magnet?

PSEB Class 10 Biology Solutions For A Student Connects A Coil Of Wire With A Sensitive Galvanometer

2. A conducting rod AB moves across two magnets as shown in the figure and the needle in the galvanometer deflects momentarily. What is the name of this physical phenomenon?

PSEB Class 10 Biology Solutions For A Conducting Rod AB Moves Across Two Magnets

3. A bar magnet is pushed steadily into a long solenoid connected to a sensitive meter.

PSEB Class 10 Biology Solutions For A Bar Magnet Is Pushed Steadily Into A Long Solenoid Connected To A sensitive Meter

Answer:

  1. The deflection in the galvanometer can be seen if the bar magnet moves towards or away from the coil parallel to the axis of the coil.
  2. If the needle of the galvanometer deflects, it means there is a change in a magnetic field and current is induced.
  3. By Faraday’s law of electromagnetic induction, the e.m.f. induced in a conductor is proportional to the rate of change of magnetic lines of force linking the circuit. Hence, by pushing the magnet faster, the rate of change of magnetic lines will increase. This results in larger induced e.m.f.., and hence, larger deflection of the meter.