Class 10 Science · Chapter 6

Control and Coordination

286 Class 10 Science questions on Control and Coordination from the NCERT textbook, NCERT Exemplar and CBSE board papers 2018–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 10 of 15

1. Q181 CBSE 2024
   Name one directional ​growth ​movement each ​in response ​to chemicals and ​water ​in plants. Write an example for ​each of them.
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   Chemotropism, for example the pollen tube growing towards the ovule; hydrotropism, for example roots growing towards water.

   In response to chemicals: chemotropism. Example: the pollen tube grows from the stigma through the style towards the ovule. In response to water: hydrotropism. Example: the roots of a plant grow towards water in the soil. In both, the plant part grows towards the stimulus.

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2. Q182 CBSE 2024
   Where ​are auxins ​synthesized ? How ​do they promote ​phototropism ​?
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   Auxins are synthesised at the shoot tip; they collect on the shady side, making its cells grow longer, so the shoot bends towards light.

   Auxins are synthesised at the shoot tip. When light falls on a shoot from one side, auxin diffuses towards the shady side of the shoot. This higher concentration of auxin stimulates the cells on the side away from the light to grow longer than the cells on the lit side, so the shoot bends towards the light. This is how auxin brings about phototropism.

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3. Q183 CBSE 2024
   How ​is ​the movement of leaves of a sensitive plant different ​from the downward ​movement ​of ​the roots ​?
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   Leaves of the sensitive plant respond to touch, quickly and without growth; roots respond to gravity by slow growth movement (positive geotropism).

   Leaves of the sensitive plant versus downward movement of roots: 1. Stimulus: The leaves respond to touch; the roots respond to gravity. 2. Growth: No growth is involved in the leaf movement, since the cells change shape by changing the amount of water in them; the root movement is a growth movement (positive geotropism). 3. Speed: The leaf movement is very quick; the root movement is slow. 4. Direction: The leaf movement is not directed by the stimulus; the root grows in the direction of the pull of gravity.

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4. Q184 CBSE 2024
   In ​the diagram given ​below, ​name ​the labelled ​parts X and ​Y. Mention ​one function for each.

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   X is the sensory neuron, carrying impulses from the receptor to the spinal cord; Y is the motor neuron, carrying them to the muscle.

   X is the sensory neuron (sensory nerve): it carries the nerve impulse from the receptor in the skin of the hand, which senses the heat, to the spinal cord. Y is the motor neuron (motor nerve): it carries the impulse from the spinal cord, after the relay neuron has passed it on, to the effector, the muscle in the arm, which contracts and pulls the hand away.

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5. Q185 CBSE 2024
   There ​is ​a hormone which regulates carbohydrate, protein and fat ​metabolism in our body. Name the hormone and the gland which secretes ​it. ​Why is it important for us to have iodised ​salt in our diet?
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   Thyroxin is secreted by the thyroid gland, which needs iodine from iodised salt to make it; lack of iodine causes goitre.

   Hormone: Thyroxin. Gland: Thyroid gland. Iodised salt is important because iodine is necessary for the thyroid gland to make thyroxin. If iodine is deficient in our diet, we may suffer from goitre, one of whose symptoms is a swollen neck.

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6. Q186 CBSE 2024
   Name ​the ​parts of the nervous ​system ​which are involved in the following activities :

   1. (i)Maintaining ​body posture
   2. (ii)Salivation
   3. (iii)Hunger
   4. (iv)​Answering ​a ​question
   Show answer

   Posture is controlled by the cerebellum, salivation by the medulla, hunger by the fore-brain's hunger centre, and answering a question by the cerebrum.

   (i) Maintaining body posture: the cerebellum (hind-brain). (ii) Salivation: the medulla (hind-brain). (iii) Hunger: the hunger centre in the fore-brain (hypothalamus). (iv) Answering a question: the cerebrum, the thinking part of the fore-brain.

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7. Q187 CBSE 2024
   What are ​plant hormones ​? Name one plant ​hormone each responsible for

   1. (i)​phototropism and
   2. (ii)​promotion of ​cell division.
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   Plant hormones are chemical compounds that coordinate growth and responses; auxin is responsible for phototropism and cytokinin for cell division.

   Plant hormones (phytohormones) are chemical compounds produced in plants which help to coordinate growth, development and responses to the environment; they are made in one part of the plant and diffuse to the part where they act. (i) Phototropism: auxin. (ii) Promotion of cell division: cytokinin.

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8. Q188 CBSE 2024
   In ​which region ​of the ​brain is

   1. (i)medulla and
   2. (ii)cerebrum located ​? State one ​function ​of ​each.
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   The medulla lies in the hind-brain and controls involuntary actions; the cerebrum lies in the fore-brain and controls voluntary actions.

   (i) The medulla is located in the hind-brain; it controls involuntary actions such as blood pressure, salivation and vomiting. (ii) The cerebrum is located in the fore-brain; it is the main thinking part of the brain and controls voluntary actions.

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9. Q189 CBSE 2024
   Name ​a hormone ​that promotes the growth ​of tendrils and explain how they help ​a ​pea ​plant to climb up other plants.
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   Auxin; the tendril part touching a support grows less rapidly, so it coils round the support and the pea plant climbs.

   Hormone: auxin, which promotes growth by helping cells grow longer. Tendrils are sensitive to touch: when a tendril touches a support, the part in contact with the support grows less rapidly than the part away from it. This unequal growth makes the tendril circle round the support and cling to it, so the pea plant climbs up other plants or fences.

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10. Q190 CBSE 2024
    Name the part of human brain which is ​responsible ​for the ​following ​actions:

    1. (i)Thinking
    2. (ii)Blood pressure
    3. (iii)Maintaining posture and balance
    4. (iv)​Salivation
    Show answer

    The cerebrum controls thinking, the medulla controls blood pressure and salivation, and the cerebellum maintains posture and balance.

    (i) Thinking: Fore-brain (cerebrum). (ii) Blood pressure: Medulla, in the hind-brain. (iii) Maintaining posture and balance: Cerebellum, in the hind-brain. (iv) Salivation: Medulla, in the hind-brain.

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11. Q191 CBSE 2024
    Name ​the organ/part of ​a plant ​which shows:

    1. (i)Positive hydrotropism
    2. (ii)​Positive ​phototropism
    3. (iii)​Negative geotropism
    4. (iv)Positive ​chemotropism
    Show answer

    Root shows positive hydrotropism, shoot shows positive phototropism and negative geotropism, and the pollen tube shows positive chemotropism.

    (i) Positive hydrotropism: Root. (ii) Positive phototropism: Shoot (stem). (iii) Negative geotropism: Shoot (stem). (iv) Positive chemotropism: Pollen tube, which grows towards the ovule.

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12. Q192 CBSE 2024
    Taking the ​example of any ​two animal ​hormones ​along with their gland of secretion, explain how these hormones help ​

    1. (i)in growth and development and
    2. (ii)regulate metabolism, in ​the body.
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    Growth hormone from the pituitary regulates growth and development; thyroxin from the thyroid regulates carbohydrate, protein and fat metabolism.

    (i) Growth hormone, secreted by the pituitary gland, regulates the growth and development of the body; a deficiency of it in childhood leads to dwarfism. (ii) Thyroxin, secreted by the thyroid gland, regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth; iodine is essential for making thyroxin, and a lack of iodine in the diet can cause goitre.

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13. Q193 CBSE 2024
    Name ​a plant growth hormone ​synthesized ​at the shoot tip. Explain ​its effect on the ​growth of a ​plant ​in ​response to light.
    Show answer

    Auxin, made at the shoot tip, diffuses to the shaded side and makes those cells grow longer, so the shoot bends towards light.

    The hormone is auxin. When light falls on a shoot from one side, the auxin made at the shoot tip diffuses towards the shaded side of the shoot. This higher concentration of auxin makes the cells on the shaded side grow longer than those on the side facing the light, so the shoot bends towards the light (phototropism).

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14. Q194 CBSE 2024
    Define reflex action. With the help of ​a flow ​chart show ​the path ​of a reflex action ​such as sneezing.
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    A reflex action is a sudden, automatic, involuntary response to a stimulus, as in sneezing when dust irritates the nose.

    Reflex action: A sudden, automatic and involuntary response of the body to a stimulus, made without conscious thinking; for example, sneezing when dust enters the nose. Flow chart: Stimulus (dust or pepper irritating the nose) → Receptors in the lining of the nose → Sensory neuron → Relay neuron in the central nervous system (for sneezing, the hind-brain) → Motor neuron → Effectors (muscles of the chest and the diaphragm) → Response (sneezing: air is forced out through the nose and mouth).

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15. Q195 CBSE 2024
    1. (a)​List two constituents of ​Central Nervous ​System ​(CNS). How are these ​components protected from injuries ?
    2. (b)Write two limitations of ​the ​use of electrical impulses.
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    The CNS is the brain and spinal cord, protected by the skull and backbone; electrical impulses reach only nerve-connected cells and need reset time.

    (a) The two constituents of the CNS are the brain and the spinal cord. The brain is placed inside a bony box, the skull, and inside it the brain is contained in a fluid-filled balloon that provides further shock absorption; the spinal cord is protected by the vertebral column (backbone). (b) (i) Electrical impulses reach only those cells that are connected by nervous tissue, not every cell of the body. (ii) Once a cell has generated and transmitted an impulse, it takes some time to reset its mechanism before it can generate and transmit a new one, so cells cannot create and transmit electrical impulses continually.

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16. Q196 CBSE 2024
    Write ​the ​name and location ​of a hormone ​which helps ​a person to respond when chased ​by a dog. Mention the responses in the body which help him to ​deal with ​the situation.
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    Adrenaline, secreted by the adrenal glands on top of the kidneys, speeds the heart and breathing and diverts blood to the skeletal muscles.

    The hormone is adrenaline, secreted by the adrenal glands, which lie on top of the kidneys; it is released directly into the blood. Responses: (1) The heart beats faster, supplying more oxygen to the muscles. (2) The muscles around the small arteries of the skin and digestive system contract, so blood is diverted to the skeletal muscles. (3) The breathing rate increases as the diaphragm and rib muscles contract faster. Blood pressure also rises. Together these responses prepare the body to run away or to fight.

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17. Q197 CBSE 2024
    Name the

    1. (i)hormone ​released, and the
    2. (ii)​gland which secretes it ​in ​human beings during scary situations. Explain how our body responds ​to ​enable it ​to deal with such situations.
    Show answer

    Adrenaline from the adrenal glands speeds the heart and breathing and diverts blood to the muscles, so the body can fight or run away.

    (i) Adrenaline. (ii) The adrenal glands, which lie on top of the kidneys. Adrenaline is secreted directly into the blood and carried to different parts of the body; its target organs include the heart. The heart beats faster, so more oxygen is supplied to our muscles. The blood supply to the digestive system and the skin is reduced, because the muscles around the small arteries in these organs contract, and this diverts blood to the skeletal muscles. The breathing rate increases because of the contractions of the diaphragm and the rib muscles. Together these responses prepare the body to deal with the situation, whether by fighting or by running away.

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18. Q198 CBSE 2024
    Name the plant ​growth ​hormone which ​is synthesized at the ​shoot ​tip. Explain why the shoot ​of a potted plant bends towards light coming from ​a window.
    Show answer

    Auxin, made at the shoot tip, moves to the shaded side and makes those cells grow longer, so the shoot bends towards the light.

    The hormone is auxin. Light from the window falls on the shoot from one side only. Auxin, synthesised at the shoot tip, diffuses towards the shaded side of the shoot, the side away from the light. This higher concentration of auxin stimulates the cells on the shaded side to grow longer than the cells on the side facing the light. Because the shaded side grows more, the shoot bends towards the light; this response is positive phototropism.

    Step-by-step solution →
19. Q199 CBSE 2024
    (i) Distinguish between hormonal co-ordination in plants ​and animals. (ii) ​Which part ​of ​the brain is responsible for –

    1. (1)​intelligence
    2. (2)​riding a bicycle
    3. (3)vomiting
    4. (4)controlling hunger (iii) How ​is brain and spinal-cord protected against mechanical injuries ?
    Show answer

    Plant hormones lack glands while animal hormones come from endocrine glands; cerebrum, cerebellum, medulla and hypothalamus control the four activities; cranium and backbone protect.

    (i) Plants: hormones are made by cells in particular regions, such as auxin at the shoot tip, with no special glands. Animals: hormones are made by specialised endocrine glands, such as the pituitary, thyroid and adrenal glands. Plants: the hormones diffuse from cell to cell to the area where they act. Animals: the hormones are secreted directly into the blood and carried to target organs. Plants: they mainly control growth and development, so the responses are slow. Animals: they control growth, metabolism, reproduction and quick responses to emergencies, work with the nervous system, and are regulated by feedback mechanisms. (ii) (1) Intelligence: cerebrum (fore-brain); (2) Riding a bicycle: cerebellum (hind-brain); (3) Vomiting: medulla (hind-brain); (4) Controlling hunger: hypothalamus (fore-brain). (iii) The brain lies inside a bony box, the cranium (skull), and within it is enclosed in fluid-filled membranes that absorb shocks. The spinal cord is protected by the vertebral column (backbone), which surrounds it.

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20. Q200 CBSE 2024
    1. (i)Define a reflex arc. Why have reflex arcs evolved in ​animals? Trace ​the sequence of events ​which occur, when you ​suddenly touch a hot object.
    2. (ii)​Name the part of nervous system which helps in communication between the central nervous ​system and other parts of the body. What are the two components of ​this system?
    Show answer

    A reflex arc gives a quick response without waiting for the brain; the peripheral nervous system has cranial and spinal nerves.

    (i) A reflex arc is the pathway of a reflex action: the connection, made in the spinal cord, between the nerves that detect a stimulus (input) and the nerves that move the muscles (output). Reflex arcs have evolved because the thinking process of the brain is not fast enough for a quick response; they work efficiently even in animals that have little or none of the complex neuron network needed for thinking. On touching a hot object: heat receptors in the skin detect the heat → the sensory neuron carries the impulse to the spinal cord → a relay neuron passes it to a motor neuron → the motor neuron carries it to the muscles of the arm (effector) → the muscles contract and the hand is withdrawn. The information also goes on to the brain. (ii) The peripheral nervous system. Its two components are the cranial nerves, arising from the brain, and the spinal nerves, arising from the spinal cord.

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