CBSE Class 10 Science Control and Coordination VBQs Set 04

A & R Questions

Question. Assertion : Auxins are found in the growing tips of the plant.
Reason : The concentration of auxin is highest at the tip of the root.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
Answer: (c) The auxin is found in the growing tips of the plant. That is, in the tip of the coleoptile, in buds and in the growing tips of leaves and roots. The concentration of auxin found at the tip of the root is significantly lower than the concentration found at the tip of the coleoptile.

Question. Assertion : Brain and spinal cord has a common covering.
Reason : Both the brain and spinal cord possess meninges.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
Answer: (a) Both the brain and spinal cord are the main structures of central nervous system which are completely covered by three connective tissue membranes. These are called piamater, arachnoid mater and duramater. Together, they are known as meninges.

Multiple Choice Questions

Question. Name the plant hormone which act as plant growth inhibitor.
(a) Auxin
(b) Gibberellin
(c) Abscisic acid
(d) Cytokinin
Answer: (c) Abscisic acid is a plant hormone which acts as a growth inhibitor. Growth inhibitors retard the growth of plants.

Question. Which of the following is a reflex action?
(a) Coughing
(b) Blinking of eyes
(c) Knee-jerk
(d) All of the options
Answer: (d) All of the options

Question. Which part of the brain regulates the body temperature?
(a) Hypothalamus
(b) Thalami
(c) Pituitary
(d) Medulla oblongata
Answer: (a) Hypothalamus is the part of brain which regulates body temperature. It has control center for hunger, thirst, fatigue, sleep, sweating and emotions. It secretes neurohormones which regulate secretions of pituitary.

Question. OR
Which one of the following does not secrete any hormone?
(a) Thyroid
(b) Ovary
(c) Testes
(d) Spleen
Answer: (d) Spleen is not a gland and hence it does not secrete any hormone. Thyroid, ovary and testes secrete hormones.

Question. Name the gland having both exocrine and endocrine regions.
(a) Thyroid
(b) Pancreas
(c) Adrenal gland
(d) Pituitary
Answer: (b) Pancreas contain exocrine and endocrine regions. So, pancreas is also known as heterocrine gland.

Question. Which of the following endocrine glands is unpaired?
(a) Adrenal
(b) Testes
(c) Pituitary
(d) Ovary
Answer: (c)

VSA Type Questions

Question. Why is the use of iodised salt advisable?
Answer: Iodine from the iodised salt is absorbed in our body which helps in the formation of thyroxine hormone secreted by thyroid gland. Thyroxine regulates the metabolism of carbohydrate, protein and fat in our body and is responsible for the growth and development of body.

Question. Why is pituitary gland called “master gland”?
Answer: Pituitary gland is called “master gland” because it controls and coordinates the secretions of all the other endocrine glands.

Question. Name the hormone responsible for:
(i) Phototropic movement of plant
(ii) Promoting cell division in plants.
Answer: (i) Auxin (ii) Cytokinin

SA I Type Questions

Question. What are hormones? Name the hormone secreted by thyroid gland and state its function.
Answer: Hormones are the chemical substances secreted by endocrine glands. They regulate biological processes in living organisms. Thyroid gland secrete three hormones : thyroxine, triiodothyronine and calcitonin.
Thyroxine and triiodothyronine maintain the basal metabolic rate (BMR) of the body by regulating the rate of oxidation of carbohydrates, fats and proteins and production of energy in our body. They promote growth of body tissues and development of mental faculties. Calcitonin regulates the concentration of calcium and phosphorus in the blood.

Question. Give the source and function of estrogen.
Answer: Estrogen is secreted by the ovaries. It regulates the growth and functioning of secondary sexual characters of female.

Question. Mention two special properties of a neuron.
Answer: Two special properties of a neuron are :
(i) It does not divide.
(ii) It does not repair, when injured.

Question. Give the difference between sensory and motor nerves.
Answer: The main difference between sensory nerve and motor nerve is that the sensory nerve takes the information from receptors and transmits it to brain and motor nerve transmits the information for action to be taken from brain to the effector organs, i.e., muscles.

Question. OR
Why do the leaves of ‘Touch me not’ plant (Mimosa pudica) droop down when touched?
Answer: Leaves of ‘touch me not’ plant droop down in response to touch. It is an example of nastic movement. In such movements, plant cells change shape by changing the amount of water in them (turgor changes) resulting in folding up and drooping of leaves.

Question. Which part of the brain controls involuntary actions? Write the function of any two regions of it.
Answer: Many of the involuntary actions are controlled by hindbrain. It consists of three parts called cerebellum, pons varolli and medulla oblongata.
(i) Cerebellum is responsible for precision of voluntary actions and maintaining the posture and balance of the body.
(ii) Medulla oblongata controls involuntary actions such as blood pressure, salivation, swallowing and vomiting, etc.

SA II Type Questions

Question. Design an experiment to demonstrate that the roots bend in the direction of water stimulus.
Answer: The given experiment demonstrates the response of roots in the direction of water stimulus. Take two glass troughs A and B and fill each one of them two-third with soil. In trough A, plant a tiny seedling and water it daily whereas in trough B, plant a similar seedling and also place a small ‘clay pot’ inside the soil. Do not water the soil (in trough B) but put some water in the clay pot and bury it in the soil and leave it for a few days. Now, dig up the soil carefully from both the troughs without damaging the roots of seedlings.
Result : The roots of seedling in trough A will be straight because it gets water from all sides as soil is watered uniformly. On the other hand, the roots of seedling in trough B will be bent towards the right side because roots get water oozing out from the clay pot which is kept on the right side. This experiment proves that the roots of a plant grow towards water, i.e., positively hydrotropic.

Question. What is ‘phototropism’? How does it occur in plants? Describe an activity to demonstrate phototropism.
Answer: Phototropism is the directional movement or orientation of the plant part in response to light stimulus. If the plant part moves towards light, it is called positive phototropism. For example, stem or shoot of a growing plant moves towards light and thus shows positive phototropism. Alternatively, if the plant part moves away from light, it is called negative phototropism. E.g., roots of a plant move away from light thus show negative phototropism. Phototropic movement in plant is caused due to the action of auxin hormone.
Phototropism can be demonstrated by the following activity: Take two potted plants and place one plant (A) in the open so that it receives the sunlight. On the other hand, place the other plant (B) in a room near the window in such a way that it receives sunlight from one side only, i.e., through the window. After some days, observe both the plants and you will notice that the first plant (A) has grown up straight towards light. However, the second plant (B) has grown by bending towards the light. Thus, we can conclude from this experiment that the stem of plant responds to light by showing growth movement towards light (positive phototropism).

Question. Compare hormonal and nervous mechanism for control and coordination.
Answer: The comparison between hormonal and nervous coordination mechanism are as follows:

Question. How does our body respond when adrenaline is secreted into the blood?
Answer: In normal situation, adrenaline is secreted in small amount. It is secreted in large amounts when a person is frightened, or mentally disturbed. When it reaches the heart, it beats faster to supply more oxygen to our muscles. The breathing rate also increases due to the contraction of diaphragm and rib muscles. It also raises the blood pressure and allows more glucose to enter into the blood. All these responses together enable our body to deal with the emergency situations.

LA Type Questions

Question. What are reflex actions? Give two examples. Explain a reflex arc.
Answer: Reflex action is defined as an unconscious, automatic and involuntary response of effectors, i.e., muscles and glands, to a stimulus, which is monitored through the spinal cord. For example, (i) blinking of eyes in response to a foreign particle that has entered into the eyes and (ii) sneezing or coughing, if any unwanted particle enters into the nose or throat.
Reflex arc is the pathway taken by the nerve impulses and responses in a reflex action, i.e., from the receptor organs like skin to the spinal cord and from the spinal cord to the effector organs like muscles. The journey of reflex action is called reflex arc. The pathway of reflex arc are :
(i) Receptor organ like skin perceives the stimulus and activates a sensory nerve impulse.
(ii) Sensory (afferent) nerve carries message in the form of sensory impulse to the spinal cord.
(iii) The spinal cord acts as modulator.
(iv) The neurons of spinal cord (relay neurons) analyse sensory impulses and transmit them to motor neuron.
(v) Motor (efferent) nerve conducts these impulses from central nervous system to the effectors.
(vi) Effectors like leg muscles respond by pulling back the organ away from the stimulus.

Question. (a) A gland secretes a particular hormone. Deficiency of this hormone in the body causes a particular disease in which the blood sugar level rises.
(i) Name the gland and the hormone secreted by it.
(ii) Mention the main role played by this hormone.
(iii) Name the disease caused due to deficiency of this hormone.
(b) Differentiate between endocrine glands and exocrine glands.
Answer: (a) (i) The gland is pancreas and the hormone secreted by it is insulin. (ii) It helps in regulating blood sugar (glucose) level. (iii) The deficiency of insulin causes diabetes. In this disease, the patient excretes sugar (glucose) in urine, feels excessive thirst and also does excessive urination.
(b) Differences between endocrine and exocrine glands are as follows:

Question. OR
(a) Differentiate between sensory neurons and motor neurons.
(b) How is brain protected in our body?
(c) Name the part of the brain responsible for precision of voluntary action and maintaining body posture and balance of the body.
Answer: (a) Sensory neurons carry sensory impulse from receptor to central nervous system through their axons. These neurons occur in sense organs and receive stimuli by their dendrites. Motor neurons carry impulse from central nervous system to effector organ. The dendrites of these neurons synapse with axons of sensory neurons in central nervous system.
(b) Human brain is lodged in a bony case, the cranium which protects it from mechanical injuries. It is wrapped in three sheets of connective tissue, known as meninges. The space between the meninges is filled with cerebrospinal fluid which help the brain in absorption of shocks.
(c) Cerebellum is responsible for precision of voluntary action and maintaining the posture and balance of the body.

Question. List the functions of testosterone and estrogen.
Answer: Testosterone serves following functions:
(i) It stimulates the growth and development of male accessory glands, e.g., prostate, seminal vesicles, etc.
(ii) It stimulates the development of secondary sexual characters in males, e.g., moustache, beard, hair on body, deepening of voice, broadening of shoulders, enlarged and stronger bones and muscles.
(iii) It stimulates the formation of sperms (spermatogenesis) in the seminiferous tubules of testes.
Estrogen performs following functions:
(i) It stimulates the formation of ova (oogenesis) in the ovary.
(ii) It stimulates the development of accessory sexual characters such as enlargement of breasts during puberty, broadening of pelvis, growth of pubic and axillary hair, onset of menstrual cycle.