CBSE Class 10 Science Control and coordination Sure Shot Questions Set 02

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CONTROL AND COORDNATION

ASSIGNMENT QUESTIONS SET - 2
CHAPTER - 7
CONTROL AND COORDINATION

1. Drastic changes of body features associated with puberty are mainly because of secretion of
a. Estrogen from testes and testosterone from ovary
b. Estrogen from adrenal gland and testosterone from pituitary gland
c. Testosterone from testes and estrogen from ovary
d. Testosterone from thyroid gland and estrogen from pituitary gland

Answer: c. Testosterone from testes and estrogen from ovary

Teacher's Note:
a) Testes in males produce testosterone, which causes male secondary sexual characters.
b) Ovaries in females produce oestrogen, which causes female features such as breast development.

2. Learning is related to
a. Hypothalamus
b. Thalamus
c. Cerebrum
d. Cerebellum

Answer: c. Cerebrum

Teacher's Note:
a) Learning, memory and intelligence are functions of the cerebrum, the largest part of the fore brain.
b) The cerebellum controls balance, not learning.

3. Which of the following statements about transmission of nerve impulse is incorrect?
a. Nerve impulse travels from dendritic end towards axonal end
b. At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron
c. The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron
d. A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells

Answer: b. At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron

1. In a neuron the impulse travels from the dendrite to the axon end, and at the axon end chemicals are released.
2. Statement (b) reverses this direction, so it is the incorrect statement.
3. Hence, the correct option is (b).

Teacher's Note:
a) Chemicals (neurotransmitters) are released at the axonal end, not at the dendritic end.
b) Check the direction of impulse flow: dendrite, cell body, axon, axon end.

4. Which of the following organs is not controlled by autonomous nervous system ?
a. Heart
b. Uterus
c. Glands
d. Eyes

Answer: d. Eyes

1. The autonomic nervous system controls the heart, uterus and glands, which work without conscious control.
2. The movement of the eyeballs is under voluntary (somatic) control, so the eyes are not controlled by the autonomic system as a whole.
3. Hence, the correct option is (d).

Teacher's Note:
a) The autonomic system does control the pupil and lens muscles of the eye, which is why students sometimes choose another option.
b) Heart rate, gut movement and gland secretion are classic examples of autonomic control.

5. The substance that triggers the fall of mature leaves and fruits from plants is due to
a. Auxin
b. Gibberellins
c. Abscissic acid
d. Cytokinin

Answer: c. Abscissic acid

Teacher's Note:
a) Abscisic acid (ABA) promotes abscission, the shedding of leaves and fruits.
b) The printed spelling "Abscissic" is a typing error for "Abscisic acid".

6. The typical neuronal resting membrane potential measures between
a. 40 mv to -80 mv
b. 30 mv to -80 mv
c. 40 mv to -90 mv
d. 40 mv to -70 mv

Answer: d. 40 mv to -70 mv

1. The resting membrane potential of a typical neuron is about -70 mV.
2. Option (d) is the only range that is centred on this value and matches the textbook figure.
3. Hence, the correct option is (d).

Teacher's Note:
a) The negative sign shows that the inside of the membrane is negative relative to the outside.
b) Options (a) to (c) use ranges that are too wide or too far from the typical value.

7. The growth of tendril in pea plants is due to
a. Effect of light
b. Effect of gravity
c. Rapid cell divisions in tendiillar cells that are away from the support
d. Rapid cell divisions in tendrillar cells in contact with the support

Answer: c. Rapid cell divisions in tendiillar cells that are away from the support

1. When the tendril touches a support, the cells on the side in contact with the support grow more slowly.
2. The cells on the side away from the support grow and divide faster, so the tendril coils around the support.
3. Hence, the correct option is (c).

Teacher's Note:
a) This response to touch is called thigmotropism.
b) The printed word "tendiillar" is a typing error for "tendrillar" in the option.

8. In reflex action, the reflex arc is formed by
a. Muscles - receptor - brain
b. Muscles - effector - brain
c. Receptor - spinal cord - muscles
d. Spinal cord - receptor - muscles

Answer: c. Receptor - spinal cord - muscles

1. In a reflex arc the impulse starts at the receptor and travels through the sensory neuron to the spinal cord.
2. The spinal cord sends the impulse through the motor neuron to the effector muscle.
3. Hence, the correct option is (c).

Teacher's Note:
a) The brain is not part of the basic reflex arc, which is why options (a) and (b) are wrong.
b) Muscles are effectors, which act at the end of the arc.

9. Which of the following statements are true about brain?
i. The main thinking part of brain is hind brain
ii. Centers of hearing, smell, memory, sight etc. are located in fore brain
iii. Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hind brain
iv. Cerebellum does not control posture and balance of the body
a. (i) and (ii)
b. (i), (ii) and (iii)
c. (ii) and (iii)
d. (iii) and (iv)

Answer: c. (ii) and (iii)

1. Statement (i) is false, because thinking is done by the cerebrum of the fore brain.
2. Statement (ii) is true, because the centres of hearing, smell, memory and sight are in the fore brain.
3. Statement (iii) is true, because the medulla controls salivation, vomiting and blood pressure.
4. Statement (iv) is false, because the cerebellum controls posture and balance.
5. Hence, the correct option is (c).

Teacher's Note:
a) The fore brain is the main thinking centre.
b) The medulla lies in the hind brain and controls many involuntary actions.

10. Which of the following statements is correct about receptors?
a. Gustatory receptors detect taste while olfactory receptors detect smell
b. Both gustatory and olfactory receptors detect smell
c. Auditory receptors detect smell and olfactory receptors detect taste
d. Olfactory receptors detect taste and gustatory receptors smell

Answer: a. Gustatory receptors detect taste while olfactory receptors detect smell

1. Gustatory receptors on the tongue detect taste.
2. Olfactory receptors in the nose detect smell.
3. Hence, the correct option is (a).

Teacher's Note:
a) Auditory receptors in the ear detect sound, not smell.
b) Taste and smell work together, which is why food tastes flat when you have a cold.

11. Which two organs are connected by pons with the help of transverse band of nerves?
a. Nerves of brain and spinal cord
b. Both the cerebral hemispheres
c. Cerebellum and central nervous system
d. Sympathetic and parasympathetic

Answer: c. Cerebellum and central nervous system

1. The pons is a part of the hind brain that lies between the medulla and the midbrain.
2. Its transverse band of nerve fibres links the cerebellum with the rest of the central nervous system.
3. Hence, the correct option is (c).

Teacher's Note:
a) The pons acts as a bridge that carries messages between the cerebellum and the brain stem.
b) The two cerebral hemispheres are connected by the corpus callosum, not by the pons.

12. Electrical impulse travels in neuron from:
a. Dendrite→axon→axon end→cell body
b. Cell body→Dendrite→axon→axon end
c. Dendrite→cell body→axon→axon end
d. Axon end→axon→cell body→Dendrite

Answer: c. Dendrite→cell body→axon→axon end

1. The impulse is received by the dendrites.
2. It passes through the cell body, then along the axon to the axon end.
3. Hence, the correct option is (c).

Teacher's Note:
a) The direction is always from dendrite to axon end inside one neuron.
b) Option (d) reverses the path, which is never the case in a neuron.

13. The plant hormone which is essential for cell division is
(a) Ethylene
(b) Auxin
(c) Gibberellin
(d) Cytokinin

Answer: (d) Cytokinin

Teacher's Note:
a) Cytokinins are produced mainly in roots and move up the plant.
b) Cytokinins also delay ageing of leaves.

14. The activities of the internal organs are controlled by the
(a) Central Nervous System
(b) Peripheral Nervous System
(c) Autonomic Nervous System
(d) None of these

Answer: (c) Autonomic Nervous System

Teacher's Note:
a) The autonomic nervous system works without conscious control and regulates heart, gut and glands.
b) The central nervous system is the brain and spinal cord, which is broader than the question asks.

15. The seat of intelligence and voluntary action in the brain is
(a) Diencephalon
(b) Cerebrum
(c) Cerebellum
(d) Medulla Oblongata

Answer: (b) Cerebrum

Teacher's Note:
a) The cerebrum is the largest part of the brain and controls thinking and voluntary movements.
b) The cerebellum controls balance, and the medulla controls involuntary actions.

16. The gap between two neurons is known as ___.
(a) synapse
(b) synopsis
(c) impulse
(d) synaptic node

Answer: (a) synapse

Teacher's Note:
a) The synapse is the junction where chemical messengers carry the impulse across.
b) "Synopsis" means a summary and has no link with nerves.

17. Which of the following is a plant hormone?
(a) Thyroxin
(b) Cytokinin
(c) Insulin
(d) Oestrogen

Answer: (b) Cytokinin

Teacher's Note:
a) Thyroxin, insulin and oestrogen are animal hormones.
b) Cytokinin is one of the five main groups of plant hormones.

18. Tropic movements are
(a) in response to light
(b) in response to gravity
(c) uni-directional
(d) non-directional

Answer: (c) uni-directional

1. Tropic movements are growth movements in which the direction of the response depends on the direction of the stimulus.
2. Hence, the correct option is (c).

Teacher's Note:
a) Light and gravity are only examples of stimuli that cause tropic movements.
b) Nastic movements are non-directional, which is the opposite of tropic movements.

19. Artifical ripening of fruit is carried out by
(a) Auxins
(b) Ethylene
(c) Abscisic acid (ABA)
(d) Gibberellins

Answer: (b) Ethylene

Teacher's Note:
a) Ethylene is a gas that speeds up ripening, which is why it is used commercially with calcium carbide in some places.
b) The printed word "Artifical" is a typing error for "Artificial".

20. Part of brain that controls respiration, heartbeat and peristalsis is ____.
(a) Cerebrum
(b) Cerebellum
(c) Pons
(d) Medulla

Answer: (d) Medulla

Teacher's Note:
a) The medulla oblongata is in the hind brain and controls many vital involuntary actions.
b) Pons helps in regulating breathing, but the medulla is the main control centre.

21. The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.

Answer: (d) all of the above.

Teacher's Note:
a) Thinking is controlled by the cerebrum, heartbeat by the medulla and balance by the cerebellum.
b) All three are parts of the brain, so option (d) is correct.

22. Which of the following hormone is released by thyroid?
(a) Insulin
(b) Thyroxin
(c) Trypsin
(d) Pepsin

Answer: (b) Thyroxin

Teacher's Note:
a) Insulin is from the pancreas, while trypsin and pepsin are digestive enzymes.
b) Thyroxine controls the rate of metabolism of the body.

23. Which body organ is surrounded by meninges?
(a) Heart and Lungs
(b) Brain & Heart
(c) Brain and Spinal Cord
(d) Spinal Cord and Lungs

Answer: (c) Brain and Spinal Cord

Teacher's Note:
a) Meninges are protective membranes that cover the brain and the spinal cord.
b) The heart and lungs are protected by the rib cage, not by meninges.

24. Part of brain that controls muscular co-ordination is ____.
(a) Cerebrum
(b) Cerebellum
(c) Pons
(d) Medulla

Answer: (b) Cerebellum

Teacher's Note:
a) Cerebellum combines the signals from muscles and eyes to give smooth movement.
b) Cerebellum also helps in learning skilled movements such as writing and cycling.

25. Growth of the stem is controlled by
(a) gibberellin
(b) auxin
(c) abscisic acid
(d) cytokinin

Answer: (a) gibberellin

Teacher's Note:
a) Gibberellins cause stem elongation by increasing cell division and cell elongation.
b) Auxin also influences stem growth, but gibberellin is the main hormone for stem elongation in this option set.

26. Wilting of leaves is caused by which hormone?
(a) gibberellin
(b) auxin
(c) abscisic acid
(d) cytokinin

Answer: (c) abscisic acid

Teacher's Note:
a) Abscisic acid closes the stomata when water is scarce, which reduces water loss.
b) Wilting follows when plants lose too much water, and ABA is the hormone that responds to this stress.

27. Which of the following hormones contains iodine?
(a) adrenaline
(b) testosterone
(c) thyroxine
(d) insulin

Answer: (c) thyroxine

Teacher's Note:
a) Thyroxine is made from the amino acid tyrosine and iodine.
b) Lack of iodine causes a swollen thyroid gland, called goitre.

28. Which part of brain controls the posture and balance of the body?
(a) Cerebrum
(b) Cerebellum
(c) Pons
(d) Medulla

Answer: (b) Cerebellum

Teacher's Note:
a) The cerebellum uses information from the ears and muscles to keep the body balanced.
b) Walking, cycling and dancing need the cerebellum to work well.

29. Fill in the blanks.

(a) _____ is the is the structural and functional unit of the nervous system.

Answer: Neuron

Teacher's Note:
a) A neuron has a cell body, dendrites and an axon.
b) The printed text "is the is" repeats a word; the answer is the neuron.

29. (b) An automatic response to a stimulus which is not controlled by the brain is called ______.

Answer: Reflex action

Teacher's Note:
a) Reflex actions are controlled by the spinal cord.
b) Blinking and withdrawing the hand from a hot object are reflex actions.

29. (c) Chemical messengers which control and coordinate in plants and animals are called _____.

Answer: Hormones

Teacher's Note:
a) Hormones are carried by blood to their target organs.
b) Plants use phytohormones, which are also chemical messengers.

29. (d) The movement of a plant part in the direction of light is called ____.

Answer: Phototropism

Teacher's Note:
a) Shoots show positive phototropism, growing towards light.
b) Roots show negative phototropism, growing away from light.

29. (e) ________ is the movement of plant part in response to the availability of water.

Answer: Hydrotropism

Teacher's Note:
a) Roots show positive hydrotropism, growing towards water.
b) Hydrotropism is a tropic movement, so its direction depends on where water is found.

29. (f) ________ is the movement of plant part in response to the pull of earth's gravity

Answer: Geotropism (gravitropism)

Teacher's Note:
a) Roots grow downwards due to positive geotropism.
b) Stems grow upwards due to negative geotropism.

29. (g) The movement of plant part in response to certain chemicals is called ______.

Answer: Chemotropism

Teacher's Note:
a) The growth of a pollen tube towards the ovule is a common example of chemotropism.
b) Chemicals released by the ovule guide the pollen tube.

29. (h) _________ is the reflex centre of the brain.

Answer: Medulla oblongata

Teacher's Note:
a) Many reflexes such as coughing, sneezing and vomiting are controlled by the medulla.
b) The medulla is the lowest part of the brain and joins the spinal cord.

29. (i) __________ is a structure associated with both nervous system and endocrine system.

Answer: Hypothalamus

Teacher's Note:
a) The hypothalamus receives nerve signals and controls the pituitary gland through hormones.
b) It controls hunger, thirst and body temperature.

30. List the functions of testosterone and estrogen.

Answer:
1. Testosterone: controls the development of male secondary sexual characters, production of sperm and growth of muscles and bones.
2. Oestrogen: controls the development of female secondary sexual characters, growth of the uterus and the menstrual cycle, and maintains bone strength.

Teacher's Note:
a) Testosterone is produced by the testes in males.
b) Oestrogen is produced mainly by the ovaries in females.
c) The printed spelling "estrogen" is the American form of "oestrogen".

31. Write name of three hormones secreted by the pituitary gland.

Answer:
1. Growth hormone
2. Thyroid stimulating hormone (TSH)
3. Antidiuretic hormone (ADH)

Teacher's Note:
a) Other pituitary hormones include prolactin, oxytocin, FSH, LH and ACTH.
b) The pituitary is called the master gland because it controls several other glands.

32. Nervous and hormonal system together perform the function of control and coordination in human beings. Justify the statement.

Answer:
1. The nervous system sends fast electrical impulses to specific organs, which gives quick but short-lived responses.
2. The hormonal system sends chemical messengers through blood, which gives slow but long-lasting control of growth, metabolism and reproduction.
3. The hypothalamus links both systems, so together they control the body in a coordinated way.

Teacher's Note:
a) Quick response to danger is a nervous function, while growth and puberty are hormonal functions.
b) The two systems must work together to keep the body in balance.

33. What is hydrotropism?

Answer:
Hydrotropism is the growth movement of a plant part, usually a root, in response to water.

Teacher's Note:
a) Roots grow towards moist soil through hydrotropism.
b) Water is the stimulus, and the direction of growth depends on where water is.

34. What is coordination?

Answer:
Coordination is the process by which different organs and systems of the body work together in a harmonised way to respond to stimuli.

Teacher's Note:
a) Control and coordination are carried out by the nervous and hormonal systems.
b) Walking needs coordination between nerves, muscles and bones.

35. Why is the response of a plant to a stimulus not observed immediately?

Answer:
1. Plant responses depend on growth, which involves cell division and cell elongation.
2. These changes take time, so the response is slow and is not seen immediately.

Teacher's Note:
a) Animals respond fast because muscles contract quickly, but plants rely on growth.
b) Hormones move slowly through the plant, which adds to the delay.

36. What are hormones?

Answer:
Hormones are chemical messengers secreted by endocrine glands directly into the blood, which carries them to target organs to regulate their activity.

Teacher's Note:
a) Hormones are needed in very small amounts.
b) Hormones act only on specific target organs that have matching receptors.

37. What are phytohormones?

Answer:
Phytohormones are chemical substances produced in plants in very small amounts, which regulate growth and development. Examples are auxin, gibberellin, cytokinin, ethylene and abscisic acid.

Teacher's Note:
a) Phytohormones are also called plant growth regulators.
b) Unlike animal hormones, they are not made in special glands.

38. What are meanings? What are their functions? Name the fluid, which is filled in between meanings.

Answer:
1. The question word "meanings" means meninges, which are three protective membranes that cover the brain and the spinal cord.
2. Their function is to protect the brain and the spinal cord from mechanical shock and injury.
3. The fluid filled between the meninges is the cerebrospinal fluid.

Teacher's Note:
a) The printed word "meanings" is a typing error for "meninges".
b) Cerebrospinal fluid also cushions the brain and carries nutrients.

39. How does control and coordination occur in single-celled animals?

Answer:
1. A single-celled animal has no nerves or hormones, so the whole cell detects the stimulus directly.
2. The cell responds by changing its shape or moving its cytoplasm, for example, Amoeba moves away from harmful chemicals.

Teacher's Note:
a) Control in single-celled animals is carried out by the cell membrane and cytoplasm.
b) Multicellular animals need nerves and hormones because their cells are far apart.

40. Name any two phytohormones, which are growth promoters.

Answer:
1. Auxin
2. Gibberellin

Teacher's Note:
a) Cytokinin is also a growth promoter that causes cell division.
b) Auxin and gibberellin both cause cell elongation, though through different routes.

41. Name any growth inhibiting phytohormone.

Answer:
Abscisic acid (ABA)

Teacher's Note:
a) Abscisic acid stops growth and promotes dormancy in seeds and buds.
b) It is also responsible for leaf fall.

42. What makes a stem bend towards sunlight?

Answer:
1. Auxin moves to the shaded side of the stem, away from the light.
2. The cells on the shaded side elongate more, so the stem bends towards the light.

Teacher's Note:
a) This response is called positive phototropism.
b) Auxin is destroyed by light on the lit side, which adds to the effect.

43. What is the difference between a reflex action and walking?

Answer:

Teacher's Note:
a) Reflex action is a quick protective response to a stimulus.
b) Walking needs the cerebrum and cerebellum to coordinate the muscles.

44. Why is a system of control and coordination essential in living organisms?

Answer:
1. Control and coordination help organisms respond to changes in the environment, such as heat, light or danger.
2. They keep the internal conditions of the body steady and allow all organs to work together for survival.

Teacher's Note:
a) Without coordination, the body would fail to respond to threats in time.
b) This steady internal state is called homeostasis.

45. What happens at the synapse between two neurons?

Answer:
1. When the impulse reaches the axon end, chemicals called neurotransmitters are released into the synaptic gap.
2. These chemicals cross the gap and bind to receptors on the dendrite of the next neuron, which generates a new electrical impulse.

Teacher's Note:
a) The impulse crosses the synapse chemically, not electrically.
b) Acetylcholine is one of the common neurotransmitters.

46. Which part of the brain maintains posture and equilibrium of the body?

Answer:
The cerebellum maintains posture and equilibrium of the body.

Teacher's Note:
a) Cerebellum is the second largest part of the brain, located at the back.
b) Injury to the cerebellum makes walking unsteady.

47. How do we detect the smell of an agarbatti (incense stick)?

Answer:
1. The smell molecules dissolve in the mucus of the nose and bind to olfactory receptors in the nasal cavity.
2. The receptors send a nerve impulse through the olfactory nerve to the olfactory lobe of the fore brain, where smell is recognised.

Teacher's Note:
a) Olfactory receptors are nerve cells that detect odour molecules.
b) The brain is needed to recognise the smell, which is why a cold can reduce it.

48. List the functions performed by Cerebrum.

Answer:
1. Thinking, learning, memory and intelligence.
2. Control of voluntary actions and movement.
3. Receiving and interpreting sensations such as sight, hearing, smell, touch and taste.
4. Control of speech and emotions.

Teacher's Note:
a) The cerebrum is the largest and most prominent part of the brain.
b) Each part of the cerebrum has a particular function, which is studied as localisation of function.

49. Which is the largest and most prominent part of the brain.

Answer:
The cerebrum is the largest and most prominent part of the brain.

Teacher's Note:
a) The cerebrum is divided into two cerebral hemispheres.
b) Its outer layer, the cerebral cortex, is folded to fit into the skull.

50. What are the functions of cerebellum?

Answer:
1. Maintains posture and balance of the body.
2. Coordinates voluntary muscle movements so that they are smooth and accurate.

Teacher's Note:
a) Alcohol affects the cerebellum, which is why people lose balance when drunk.
b) The cerebellum does not start movements; it fine-tunes them.

51. How brain is protected inside a human body?

Answer:
1. The brain is enclosed in the bony skull (cranium).
2. It is further covered by three protective membranes called meninges, and cushioned by cerebrospinal fluid.

Teacher's Note:
a) The skull protects the brain from physical shocks.
b) The cerebrospinal fluid acts as a shock absorber.

52. What is the role of the brain in reflex action?

Answer:
1. The reflex action itself is controlled by the spinal cord and does not wait for the brain.
2. The brain is informed of the action after it has happened, so we become aware of it later.

Teacher's Note:
a) Reflexes save time because the decision is taken in the spinal cord.
b) The brain can still modify some reflexes through learning.

53. What do you mean by reflex action? Give examples of reflex actions?

Answer:
1. A reflex action is a sudden, automatic and involuntary response to a stimulus, which occurs without conscious thinking.
2. Examples: withdrawing the hand from a hot object, blinking when a bright light falls on the eye, sneezing, and the knee jerk.

Teacher's Note:
a) Reflex actions are fast and protective.
b) The knee jerk is a reflex tested by doctors to check the nervous system.

54. What are the different types of reflexes?

Answer:
1. Natural (unconditioned) reflexes, which are inborn and present from birth, such as blinking and sneezing.
2. Conditioned (learned) reflexes, which are acquired by practice, such as salivating at the sound of a bell after training.

Teacher's Note:
a) Conditioned reflexes can be learned and forgotten.
b) Pavlov's dog experiment is the classic example of a conditioned reflex.

55. What is reflex arc?

Answer:
The reflex arc is the path taken by a nerve impulse in a reflex action: receptor, sensory neuron, spinal cord, motor neuron, and effector (muscle or gland).

Teacher's Note:
a) The spinal cord is the centre of the reflex arc.
b) Ensure the order is correct: receptor first and effector last.

56. What are plant hormones?

Answer:
Plant hormones are chemical substances, produced in one part of the plant, that move to other parts in very small amounts and regulate growth and development.

Teacher's Note:
a) Plant hormones are also called phytohormones.
b) Auxin, gibberellin, cytokinin, ethylene and abscisic acid are the five main groups.

57. Who coined the term phytohormones?

Answer:
The term phytohormone was used by Frits Went and Kenneth Thimann in their 1937 book titled Phytohormones.

Teacher's Note:
a) Frits Went discovered auxin through his coleoptile experiments.
b) Students are usually asked for the name of the scientist, so Went is the expected answer.

58. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Answer:

Teacher's Note:
a) The sensitive plant folds its leaves in a few seconds when touched.
b) Shoots bend towards light over hours or days.

59. Write differences between nastic and tropic movements

Answer:

Teacher's Note:
a) Nastic movements are common in flowers and leaves.
b) Tropic movements are growth responses, while most nastic movements are turgor changes.

60. What will happen when plant is exposed to unidirectional light?

Answer:
1. The shoot bends towards the light, which is positive phototropism, because auxin collects on the shaded side and makes those cells grow faster.
2. The root bends away from the light, which is negative phototropism.

Teacher's Note:
a) Shoots and roots respond in opposite ways to the same light.
b) This response helps the shoot reach sunlight for photosynthesis.

61. What is chemotropism?

Answer:
Chemotropism is the growth movement of a plant part in response to chemicals, such as the growth of a pollen tube towards the ovule.

Teacher's Note:
a) Chemotropism is a tropic movement, so its direction depends on the chemical's position.
b) Pollen tube growth is the best-known example for exam answers.

62. Give examples of geotropism.

Answer:
1. Roots growing downwards into the soil, which is positive geotropism.
2. Shoots growing upwards away from the soil, which is negative geotropism.

Teacher's Note:
a) Gravity is the stimulus in geotropism.
b) Auxin moves to the lower side of a horizontal stem, which causes the stem to bend upwards.

63. Why do mammals like humans need an endocrinal system?

Answer:
1. The nervous system alone cannot control slow and long-lasting processes such as growth, metabolism and reproduction.
2. The endocrine system releases hormones into the blood, which act on many organs over a long time and keep the body balanced.

Teacher's Note:
a) The printed word "endocrinal" is spelt "endocrine" in standard usage.
b) Hormones are essential for puberty, which the nervous system cannot direct alone.

64. What are the limitations of nervous system in human body? How it is overcome?

Answer:
1. Nerve impulses act quickly, but their effects last only for a short time and are limited to specific organs.
2. The nervous system cannot control slow processes such as growth and development. These are overcome by the hormonal system, which acts slowly but for a long period.

Teacher's Note:
a) Nerves reach only the organs they are connected to.
b) Together, the two systems cover both short and long-term needs.

65. How does chemical coordination take place in animals?

Answer:
1. Endocrine glands secrete hormones directly into the blood.
2. The blood carries hormones to target organs, which have specific receptors and respond to them.

Teacher's Note:
a) Chemical coordination is slower than nervous coordination.
b) Insulin and adrenaline are examples of hormones that carry out this function.

66. Who coined the term hormone?

Answer:
Ernest Starling coined the term hormone in 1905.

Teacher's Note:
a) The word hormone comes from a Greek word meaning "to set in motion".
b) Starling worked with William Bayliss on secretin, the first hormone to be discovered.

67. What will happen if intake of iodine in our diet is low?

Answer:
1. Low iodine means less thyroxine is made by the thyroid gland.
2. The thyroid gland enlarges to try to make more thyroxine, which causes a swelling in the neck called goitre.

Teacher's Note:
a) Low thyroxine can also slow metabolism and cause tiredness.
b) Iodine deficiency is one of the most common causes of goitre.

68. Why is the use of iodised salt advised?

Answer:
Iodised salt supplies iodine, which the thyroid gland needs to make thyroxine, and this prevents goitre and other iodine deficiency disorders.

Teacher's Note:
a) Only a very small amount of iodine is needed each day.
b) Iodised salt should be added after cooking, since heat reduces the iodine content.

69. Name the hormone secreted by an endocrine gland during emergency? Name the gland which secretes this hormone.

Answer:
1. The hormone is adrenaline.
2. It is secreted by the medulla of the adrenal gland.

Teacher's Note:
a) Adrenaline is called the emergency hormone or the fight or flight hormone.
b) Adrenal glands sit on top of the kidneys.

70. How does adrenaline affects heart during emergency?

Answer:
1. Adrenaline increases the heart rate.
2. It increases the force of contraction of the heart, so more blood is pumped to the muscles and brain.

Teacher's Note:
a) The faster heartbeat is felt as a racing or pounding heart during fear.
b) The heart returns to normal once the emergency is over.

71. How does our body respond when adrenaline is secreted into the blood?

Answer:
1. Heart rate and breathing rate increase, and the pupils dilate.
2. Glycogen in the liver is broken down into glucose, which raises blood sugar and gives energy to the muscles.

Teacher's Note:
a) Blood flow is diverted from the gut and skin to the muscles.
b) These changes prepare the body to fight or run away from danger.

72. Which hormone is injected to a diabetic patient and why?

Answer:
Insulin is injected because the pancreas of a diabetic patient does not make enough insulin to lower the blood glucose level.

Teacher's Note:
a) Insulin helps the cells take up glucose from the blood.
b) Diabetes can be controlled by insulin, diet and exercise.

73. Why are some patients of diabetes treated by giving injections of insulin?

Answer:
1. Insulin is a protein, which would be digested in the stomach if taken by mouth.
2. An injection sends insulin directly into the blood, so it reaches the target cells unchanged.

Teacher's Note:
a) Enzymes in the stomach break down proteins into amino acids.
b) Injections are used for insulin only; some other hormones are taken orally.

74. How does our body maintain blood sugar level?

Answer:
1. When blood sugar rises, the beta cells of the pancreas release insulin, which lowers blood glucose by helping cells absorb it and storing it as glycogen.
2. When blood sugar falls, the alpha cells release glucagon, which converts glycogen into glucose and raises blood glucose.

Teacher's Note:
a) Insulin and glucagon work against each other, which is called antagonistic action.
b) This feedback keeps blood sugar in a normal range.

75. Where adrenal glands are located?

Answer:
The adrenal glands are located on the top of each kidney.

Teacher's Note:
a) This is why they are also called suprarenal glands.
b) The outer part is the cortex and the inner part is the medulla.

76. What is hyperglycemia?

Answer:
Hyperglycemia is a condition in which the blood glucose level is higher than normal.

Teacher's Note:
a) Prolonged hyperglycemia is a sign of diabetes.
b) Long-term hyperglycemia damages blood vessels, nerves and the kidneys.

77. Where thyroid gland is located?

Answer:
The thyroid gland is located in the neck, in front of the windpipe (trachea), below the larynx.

Teacher's Note:
a) The thyroid is a butterfly-shaped gland.
b) Its swelling in the neck is the sign of goitre.

78. Which endocrine gland is called master gland? Why?

Answer:
1. The pituitary gland is called the master gland.
2. It secretes hormones that control the functioning of many other endocrine glands, such as the thyroid and adrenal glands.

Teacher's Note:
a) The pituitary is controlled by the hypothalamus of the brain.
b) The pituitary is located at the base of the brain.

79. Why is pancreas a dual gland?

Answer:
1. The pancreas is an endocrine gland, because its islets of Langerhans secrete insulin and glucagon into the blood.
2. It is also an exocrine gland, because it secretes digestive enzymes into the small intestine.

Teacher's Note:
a) Being both endocrine and exocrine gives it the name dual gland.
b) The digestive juice from the pancreas is released through a duct.

80. Who introduced the term Hormones?

Answer:
Ernest Starling introduced the term hormone.

Teacher's Note:
a) Starling's 1905 lecture introduced the word to biology.
b) The same term is asked in question 66, so students should learn it once for both.

81. In Plants:

81. a) Name the two substances which are responsible for the control and coordination in plants.

Answer:
Plant hormones (phytohormones) such as auxin and gibberellin are the two substances named here, and they control growth and coordination in plants.

Teacher's Note:
a) Any two phytohormones can be written, but auxin and gibberellin are the usual pair.
b) Plants have no nerves, so chemical substances do all the coordination.

81. b) What is the function of Gibberellins, Ethene and Auxins?

Answer:
1. Gibberellins: promote stem elongation, seed germination and flowering.
2. Ethene: promotes ripening of fruits and the shedding of leaves and fruits.
3. Auxins: promote cell elongation, phototropism and apical dominance.

Teacher's Note:
a) Auxins are used to make seedless fruits and rooting powders.
b) Ethene is a gas, which is why it spreads quickly through the air around ripening fruits.

81. c) What are Phytohormones? Name any two.

Answer:
1. Phytohormones are chemical substances produced in plants in very small amounts, which regulate growth and development.
2. Two examples are auxin and gibberellin.

Teacher's Note:
a) Cytokinin, ethylene and abscisic acid are other phytohormones.
b) Phytohormones move from the place of production to the place of action.

81. d) What is the difference between photoperiodism and phototropism?

Answer:
1. Photoperiodism is the response of a plant to the relative length of day and night, for example in flowering.
2. Phototropism is the growth movement of a shoot towards or away from light.

Teacher's Note:
a) Short-day and long-day plants are classified by photoperiodism.
b) Phototropism is a growth response, while photoperiodism controls timing of flowering.

81. e) What are nastic movements? Give one example.

Answer:
1. Nastic movements are non-directional movements of plant parts in response to stimuli such as touch, temperature or light intensity.
2. Example: the folding of leaves of the touch-me-not plant (Mimosa pudica) when touched.

Teacher's Note:
a) Nastic movements do not depend on the direction of the stimulus.
b) Closing of petals at night is another example.

81. f) What are the different Hormones found in Plants and their functions?

Answer:

Teacher's Note:
a) Auxin and gibberellin usually work together to produce growth.
b) Abscisic acid balances the growth-promoting hormones.

82. In Animals:

82. a) Draw a diagram of nervous system of an insect. Label the following parts: Brain, Ganglion, and Nerve Chord.

[Figure: diagram to be added. Insect nervous system with the brain above the oesophagus, a ventral nerve cord running along the length of the body, and a ganglion in each body segment on the nerve cord. Labels: Brain, Ganglion, Nerve Cord]

Answer:
The insect nervous system has a brain in the head, a double ventral nerve cord, and paired ganglia in each segment that are joined to the nerve cord.

Teacher's Note:
a) The brain of an insect is a dorsal ganglion above the gut.
b) Ganglia act as local control centres in each body segment.

82. b) Which is the structural and functional unit of nervous system? Describe with the help of a diagram.

[Figure: diagram to be added. Neuron showing dendrites branching from the cell body, the nucleus in the cell body, a long axon, the myelin sheath around the axon, and axon terminals with synaptic knobs. Labels: Dendrites, Cell body, Nucleus, Axon, Myelin sheath, Axon end]

Answer:
1. The neuron is the structural and functional unit of the nervous system.
2. It has dendrites that receive impulses, a cell body with the nucleus, and an axon that carries the impulse away from the cell body to the axon end.
3. The myelin sheath around the axon speeds up the impulse, and the axon end releases chemicals at the synapse.

Teacher's Note:
a) Nerve fibres are long axons bundled together.
b) Dendrites carry impulses towards the cell body, while axons carry them away.

82. c) "Nervous and the hormonal system together perform the function of the control and coordination in the humans". Justify.

Answer:
1. The nervous system gives quick, short-lived responses through electrical impulses, such as withdrawing the hand from heat.
2. The hormonal system gives slow, long-lasting responses through hormones, such as growth and puberty.
3. The hypothalamus joins the two systems, so the nervous and hormonal systems work together to control the body.

Teacher's Note:
a) Quick and slow responses are both needed for survival.
b) Adrenaline shows both systems at work, since nerves trigger its release during danger.

82. i) Nervous system:

82. i) 1) What are the different types of nervous systems found in human body? Mention the functions of each.

Answer:
1. Central nervous system (brain and spinal cord): receives, processes and sends out information.
2. Peripheral nervous system (cranial and spinal nerves): carries impulses between the central nervous system and the rest of the body.
3. Autonomic nervous system (sympathetic and parasympathetic): controls involuntary organs such as the heart, gut and glands.

Teacher's Note:
a) The central nervous system is the control centre of the body.
b) The autonomic system works without conscious control.

82. i) 2) Write the effects of sympathetic and parasympathetic nervous system on the following: a. Heart b. Blood Vessels c. Bronchi d. Eyes e. Gastric Bladder

Answer:

Teacher's Note:
a) Sympathetic effects prepare the body for action, while parasympathetic effects restore rest.
b) The printed phrase "Gastric Bladder" is taken as the stomach and the urinary bladder.

82. i) 3) Draw the schematic diagram of reflex arc. Define reflex action with suitable example.

[Figure: diagram to be added. Schematic reflex arc showing a receptor (skin of the finger), a sensory neuron going to the spinal cord, a relay neuron in the spinal cord, a motor neuron going to the effector (muscle of the arm). Labels: Receptor, Sensory neuron, Spinal cord, Motor neuron, Effector]

Answer:
1. Reflex action is a sudden, automatic and involuntary response to a stimulus, without conscious thinking.
2. Example: withdrawing the hand quickly when it touches a hot object.

Teacher's Note:
a) The reflex arc is the path of the impulse: receptor, sensory neuron, spinal cord, motor neuron, effector.
b) Label the spinal cord as the central point of the arc.

82. i) 4) If the parasympathetic nervous system causes constriction of pupil what will be the effect of sympathetic nervous system.

Answer:
The sympathetic nervous system will cause dilation of the pupil.

Teacher's Note:
a) The two systems have opposite effects on the same organ.
b) Dilated pupils let more light in, which helps in dim light or during fear.

82. ii) Brain:

82. ii) 1) Draw the labeled structure of human brain.

[Figure: diagram to be added. Labelled sagittal view of the human brain showing Cerebrum, Cerebellum, Medulla oblongata, Pons, Midbrain, Thalamus, Hypothalamus, Pituitary gland, Spinal cord]

Answer:
The labelled diagram must show the cerebrum (fore brain), midbrain, cerebellum, pons and medulla oblongata (hind brain), with the thalamus and hypothalamus in the fore brain and the pituitary gland at the base of the brain.

Teacher's Note:
a) Draw the brain from the side, with the cerebellum at the back.
b) The medulla joins the spinal cord at the base of the brain.

82. ii) 2) What are the four main parts of the fore brain? Give the function of each part.

Answer:
1. Cerebrum: thinking, memory, intelligence and voluntary actions.
2. Thalamus: relay centre that passes sensory information to the cerebrum.
3. Hypothalamus: controls hunger, thirst, body temperature and hormone release from the pituitary.
4. Olfactory lobes: control and analyse the sense of smell.

Teacher's Note:
a) The fore brain is the largest and most complex part of the brain.
b) The hypothalamus links the brain with the endocrine system.

82. ii) 3) What are the three parts of the mid brain and their functions?

Answer:
1. Cerebral peduncles: carry impulses between the cerebrum and the lower parts of the brain and spinal cord.
2. Corpora quadrigemina: control visual and auditory reflexes.
3. Cerebral aqueduct: a canal that passes cerebrospinal fluid through the midbrain.

Teacher's Note:
a) The midbrain lies between the fore brain and the hind brain.
b) Visual reflexes include turning the eyes and head towards a bright object.

82. ii) 4) Which part of the human brain is responsible for: Intelligence and Memory, Adjustment movement and Posture, Smell?

Answer:
1. Intelligence and memory: cerebrum.
2. Adjustment of movement and posture: cerebellum.
3. Smell: olfactory lobes of the fore brain.

Teacher's Note:
a) Intelligence and memory are linked to the cerebral cortex.
b) Smell is analysed in the olfactory lobe, which is part of the fore brain.

82. ii) 5) Give the role of Frontal lobe, temporal lobe and medulla oblongata.

Answer:
1. Frontal lobe: thinking, planning, voluntary movement and speech.
2. Temporal lobe: hearing, smell, memory and understanding speech.
3. Medulla oblongata: controls involuntary actions such as heartbeat, breathing, blood pressure, vomiting and salivation.

Teacher's Note:
a) Damage to the frontal lobe can affect speech and decision making.
b) The medulla is the vital centre of the brain, and damage to it can be fatal.

82. ii) 6) Name the different lobes found in the fore brain and give their functions.

Answer:
1. Frontal lobe: thinking, planning, voluntary movement and speech.
2. Parietal lobe: touch, pain, temperature and taste.
3. Temporal lobe: hearing, smell, memory and understanding speech.
4. Occipital lobe: vision (sight).

Teacher's Note:
a) Each cerebral hemisphere has four lobes.
b) The occipital lobe at the back of the head processes visual information.

82. ii) 7) What is EEG? What is the use of an EEG? Which radiation do they measure?

Answer:
1. EEG stands for electroencephalogram, a record of the electrical activity of the brain taken with electrodes placed on the scalp.
2. It is used to diagnose epilepsy, sleep disorders and some brain injuries.
3. An EEG does not measure radiation; it measures the electrical waves (brain waves) produced by nerve cells.

Teacher's Note:
a) The brain waves recorded are very weak electrical signals.
b) The printed question asks about radiation, but the correct answer is electrical activity.

82. iii) Endocrine Glands:

82. iv) Draw the diagram showing endocrine glands in a male body/female body and label: Pituitary, Thyroid, Adrenal, Testis/ovaries, Thalamus, and Hypothalamus.

[Figure: diagram to be added. Outline of a human body showing endocrine glands. Labels: Hypothalamus and Thalamus (brain), Pituitary (base of brain), Thyroid (neck, in front of the windpipe), Adrenal (top of each kidney), Testis (male) or Ovary (female), Pancreas (abdomen)]

Answer:
The diagram must show the hypothalamus and thalamus in the brain, the pituitary at the base of the brain, the thyroid in the neck, the adrenal glands on top of the kidneys, and the testes in a male body or the ovaries in a female body.

Teacher's Note:
a) Thalamus is a relay centre, not an endocrine gland, but it is shown with the brain structures.
b) The adrenal glands are placed above the kidneys, not inside them.

82. v) Name the hormone associated with a) Reduction of blood glucose in the body b) Overall metabolism of the body.

Answer:
1. a) Insulin reduces the blood glucose level.
2. b) Thyroxine controls the overall metabolism of the body.

Teacher's Note:
a) Insulin is secreted by the beta cells of the pancreas.
b) Thyroxine is produced by the thyroid gland and needs iodine.

82. vi) Write the function of testes, ovaries and epidydmis

Answer:
1. Testes: produce sperms and the male hormone testosterone.
2. Ovaries: produce ova (eggs) and the female hormones oestrogen and progesterone.
3. Epididymis: stores and matures sperms, and passes them to the vas deferens.

Teacher's Note:
a) The printed word "epidydmis" is a typing error for "epididymis".
b) The testes and ovaries are both reproductive organs and endocrine glands.

83. Mayank's father never bothered to check the brand/contents of the salt he had purchased from the market. Mayank noticed that her sister had developed swollen neck. The doctor advised her to eat Iodised Salt.
i). Name the disease from which Mayank s sister suffered.
ii). Why the doctor has advised her to eat Iodised Salt?

83. i) Name the disease from which Mayank s sister suffered.

Answer:
Goitre, a swelling of the thyroid gland caused by iodine deficiency.

Teacher's Note:
a) The swelling is in the front of the neck, where the thyroid lies.
b) Goitre is preventable by eating iodised salt.

83. ii) Why the doctor has advised her to eat Iodised Salt?

Answer:
Iodised salt supplies iodine, which the thyroid needs to make thyroxine. Adequate thyroxine reduces the swelling of the thyroid gland.

Teacher's Note:
a) Iodine is needed only in small amounts, so iodised salt is the simplest source.
b) Mayank's father should check the salt packet to make sure it is iodised.

84. Injections are given to the cattle for the production of milk.
(i). Do you think it is a right practice.
(ii). What harm is this practice causing us?

84. (i) Do you think it is a right practice.

Answer:
No, it is not a right practice, because it harms the health of the animals and of the people who drink the milk.

Teacher's Note:
a) Hormone injections are given to cows to increase milk yield.
b) Such practices are discouraged and are banned in many places.

84. (ii) What harm is this practice causing us?

Answer:
1. Hormone residues in milk may cause early puberty and hormonal imbalance in children.
2. Antibiotic residues may cause resistance to medicines, and the animals may suffer from disease.

Teacher's Note:
a) Hormone residues can affect the endocrine system of the person who drinks the milk.
b) Milk from animals given many injections may not be safe for infants.

85. Often the road accidents victims faced really a tough time due to the shortage of blood in the hospital.
i). Give suggestion to avoid shortage of blood in the blood bank.

Answer:
1. Organise regular voluntary blood donation camps in schools, colleges and offices.
2. Create a donor database and spread awareness that a healthy person can donate blood safely every few months.

Teacher's Note:
a) Blood can be donated only by healthy people above the required age and weight.
b) Blood banks should keep stocks of the most common blood groups.

86. A person is taking the insulin injection everyday.
(i). Name the disease he is suffering from.
(ii). How does healthy life style help this patient to control this disease?

86. (i) Name the disease he is suffering from.

Answer:
Diabetes mellitus.

Teacher's Note:
a) Daily insulin injections are needed in type 1 diabetes, where the pancreas makes little or no insulin.
b) Blood sugar must be checked regularly.

86. (ii) How does healthy life style help this patient to control this disease?

Answer:
1. A balanced diet with less sugar and refined carbohydrates keeps blood glucose from rising sharply.
2. Regular exercise helps the cells use glucose, and avoiding smoking and alcohol protects the heart and blood vessels.

Teacher's Note:
a) Regular meals help match insulin doses with food intake.
b) A healthy weight reduces the risk of complications such as kidney and eye damage.

87. Most of students suffer from exam stress and anxiety during exam days.
i). Suggest three good habits which students should adopt to tackle this problem.

Answer:
1. Plan the study timetable and revise in small parts to avoid last-minute pressure.
2. Do regular physical exercise, yoga or meditation to relax the mind.
3. Sleep for enough hours and eat a balanced diet, and talk to parents or teachers when worried.

Teacher's Note:
a) Breathing exercises calm the nervous system during exam stress.
b) Students who sleep well remember more of what they have studied.

88. Generally some of teenagers readily come under bad influences under peer group pressure.
(i). Why does teenagers readily come under this influence.
(ii). Suggest methods to overcome such problems.

88. (i) Why does teenagers readily come under this influence.

Answer:
1. Teenagers want acceptance and a sense of belonging among friends.
2. Hormonal changes during puberty make them emotional, and their judgement is still developing.

Teacher's Note:
a) Peer pressure is strongest during adolescence.
b) Teenagers who lack self-confidence are more easily influenced.

88. (ii) Suggest methods to overcome such problems.

Answer:
1. Build self-confidence and learn to say no firmly to unhealthy choices.
2. Choose friends carefully, and keep open communication with parents and teachers.
3. Take part in sports, hobbies and clubs that give positive goals.

Teacher's Note:
a) Role models help teenagers make good decisions.
b) Seeking help from a counsellor is a sensible step if pressure becomes too much.

89. Differentiate between (i)tropic and nastic movements. (ii)axon and dendrites (iii)cerebrum and cerebellum.

89. (i) Differentiate between tropic and nastic movements.

Answer:

Teacher's Note:
a) Tropic movements are growth responses.
b) Nastic movements are usually reversible and fast.

89. (ii) Differentiate between axon and dendrites.

Answer:

Teacher's Note:
a) The axon is covered by a myelin sheath in many neurons.
b) Dendrites form the main receiving part of the neuron.

89. (iii) Differentiate between cerebrum and cerebellum.

Answer:

Teacher's Note:
a) The cerebrum is the seat of intelligence.
b) The cerebellum is the centre of balance and fine motor skill.

90. How does the nervous tissue cause action?

Answer:
1. Nervous tissue receives a stimulus at the receptor and converts it into an electrical impulse.
2. The impulse travels along the neurons and crosses the synapses by chemical messengers, and it finally reaches a muscle or gland, which responds to bring about the action.

Teacher's Note:
a) Muscles contract and glands secrete in response to the impulse.
b) Synapses control the direction in which the impulse moves.

91. What are PHYTOHORMONES?give examples

Answer:
1. Phytohormones are chemical substances produced in plants that regulate their growth and development in very small amounts.
2. Examples: auxin, gibberellin, cytokinin, ethylene and abscisic acid.

Teacher's Note:
a) Phytohormones are also called plant growth regulators.
b) Any two examples are enough for the answer.

92. Which organ secretes hormone when the blood sugar rises? Name a digestive enzyme released by this organ.

Answer:
1. The pancreas secretes insulin when blood sugar rises.
2. A digestive enzyme released by the pancreas is trypsin.

Teacher's Note:
a) Insulin is made in the islets of Langerhans in the pancreas.
b) Amylase and lipase are other digestive enzymes made by the pancreas.

93. What will happen when plant is exposed to unidirectional light?

Answer:
1. The shoot bends towards the light, which is positive phototropism, because auxin moves to the shaded side and makes those cells grow more.
2. The root bends away from the light, which is negative phototropism.

Teacher's Note:
a) This question repeats question 60, and the same answer applies.
b) The response to light helps the shoot find sunlight for photosynthesis.

94. A particular hormone requires iodine for its synthesis. Name the endocrine gland which secretes this hormone and state its location in human body.

Answer:
1. The hormone is thyroxine, which is secreted by the thyroid gland.
2. The thyroid gland is located in the neck, in front of the windpipe, below the larynx.

Teacher's Note:
a) Thyroxine controls the rate of metabolism.
b) Iodine deficiency causes goitre.

95. How are our brain and spinal cord protected?

Answer:
1. The brain is protected by the skull and the spinal cord by the vertebral column.
2. Both are covered by the meninges and cushioned by cerebrospinal fluid.

Teacher's Note:
a) The bones of the skull and vertebrae are hard and protective.
b) Cerebrospinal fluid acts as a shock absorber.

96. Identify the glands and mention hormones produced----------
1. Gland which prepares our body to function at maximum efficiency during anger or danger.
2. gland that helps in growth of bones and muscles.
3. gland that helps in growth of secondary sexual characters in males.

Answer:
1. Adrenal gland (medulla), which produces adrenaline.
2. Pituitary gland, which produces growth hormone.
3. Testes, which produce testosterone.

Teacher's Note:
a) Adrenaline is the emergency hormone.
b) Growth hormone is also called somatotropin.
c) Testosterone is produced by the Leydig cells of the testes.

97. Mention some secondary sexual characters seen in both girls and boys during puberty.

Answer:
1. Growth of hair in the armpits and pubic region.
2. Increase in height and body weight, and oily skin with pimples.

Teacher's Note:
a) These changes are brought about by hormones released at puberty.
b) Boys also show voice breaking and facial hair, which are not seen in girls.

98. Give reasons:
a) Why we must take iodised salt?
b) Why the touch-me-not (Mimosa pudica)plant leaves droop when touched?

98. a) Why we must take iodised salt?

Answer:
Iodised salt provides iodine, which the thyroid gland needs to make thyroxine, so that goitre and other iodine deficiency disorders are prevented.

Teacher's Note:
a) Iodine is needed in very small amounts.
b) Iodised salt is the easiest way to get the required iodine.

98. b) Why the touch-me-not (Mimosa pudica) plant leaves droop when touched?

Answer:
When touched, water moves out of the cells at the base of the leaflets (pulvinus), which reduces the turgor pressure and makes the leaves droop.

Teacher's Note:
a) This is a nastic movement that is quick and reversible.
b) The leaves open again when turgor pressure is restored.

99. Name two systems which together perform function of control and coordination in human being.

Answer:
1. Nervous system
2. Endocrine (hormonal) system

Teacher's Note:
a) Nerves give fast responses, and hormones give slow responses.
b) The two systems are linked through the hypothalamus.

100. What is reflex arc?

Answer:
The reflex arc is the path of a nerve impulse in a reflex action: receptor, sensory neuron, spinal cord, motor neuron and effector.

Teacher's Note:
a) The reflex arc is the same as question 55.
b) The spinal cord is the relay centre of the arc.

101. What are the characteristics of animal hormones?

Answer:
1. Hormones are secreted by endocrine glands directly into the blood and act on specific target organs.
2. They are needed in very small amounts, act slowly and their effects last for a long time.

Teacher's Note:
a) Hormones are chemical messengers, not nerve impulses.
b) Hormones regulate growth, metabolism, reproduction and emergency responses.

102. Write the mechanism of adrenaline hormone?

Answer:
1. Adrenaline binds to receptors on the surface of target cells.
2. This activates the enzyme adenylate cyclase, which produces cyclic AMP inside the cell.
3. Cyclic AMP triggers the breakdown of glycogen into glucose, and raises heart rate and blood flow to muscles.

Teacher's Note:
a) Cyclic AMP is a second messenger that carries the signal inside the cell.
b) This mechanism explains how a small amount of adrenaline causes a large effect.

103. Why adrenaline is called emergency hormone?

Answer:
Adrenaline prepares the body for fight or flight in danger. It raises the heart rate, breathing rate and blood sugar, and diverts blood to the muscles.

Teacher's Note:
a) Adrenaline is released quickly in response to stress.
b) Its effects end once the danger has passed.

104. What is synapse?

Answer:
A synapse is the junction between the axon end of one neuron and the dendrite of the next neuron, across which the impulse passes with the help of chemicals.

Teacher's Note:
a) The gap in a synapse is called the synaptic cleft.
b) This question is also covered in question 16 and question 45.

105. What regulates the timing and amount of release of hormones?

Answer:
1. The hypothalamus and the pituitary gland regulate the timing and amount of hormone release.
2. Feedback control, in which the level of a hormone or of the substance it controls in the blood, switches its release on or off.

Teacher's Note:
a) Negative feedback keeps hormone levels within a normal range.
b) Insulin and glucagon release are regulated by the blood glucose level.

106. What is the role of Medulla?

Answer:
The medulla oblongata controls involuntary actions such as heartbeat, breathing, blood pressure, vomiting, coughing, sneezing and salivation.

Teacher's Note:
a) The medulla is the lowest part of the brain and continues into the spinal cord.
b) Damage to the medulla can stop breathing and heartbeat.

107. What is the function of cerebellum?

Answer:
The cerebellum maintains balance and posture of the body and coordinates voluntary muscle movements.

Teacher's Note:
a) The cerebellum is in the hind brain.
b) It helps us walk, run and write with smooth and accurate movements.

108. What is the function of fore brain?

Answer:
The fore brain controls thinking, memory, intelligence, voluntary actions and the sense organs of sight, hearing and smell, and it contains the hypothalamus that regulates hunger, thirst and body temperature.

Teacher's Note:
a) The cerebrum is the largest part of the fore brain.
b) The fore brain also contains the thalamus, which relays sensory information.