CBSE Class 10 Biology Control and Coordination MCQs Set 06

Answer: (d) Phytohormone

Explanation:
1. Plants have no nervous system, so their responses are controlled and coordinated by chemical messengers called phytohormones.
2. Sunlight and gravity are only stimuli.

Teacher's Note:
1. A stimulus is what the plant detects; the hormone brings about the response.
2. Plants coordinate through chemicals.

Answer: (d) adrenaline

Explanation:
1. Adrenaline increases heart rate and breathing rate, and sends more blood and oxygen to muscles.

Teacher's Note:
1. Adrenaline is the emergency hormone.
2. Insulin controls blood sugar.

Answer: (c) gaseous hormone

Explanation:
1. Ethylene is a plant hormone that is a gas at ordinary temperature. It helps in fruit ripening.

Teacher's Note:
1. Ethylene is the only gaseous plant hormone.
2. It is not an enzyme.

Answer: (a) Estrogen

Explanation:
1. Oestrogen from the ovaries brings about the changes of puberty in girls.

Teacher's Note:
1. Testosterone does this in boys.
2. Both are sex hormones.

Answer: (c) medulla in hind brain

Explanation:
1. The medulla oblongata in the hind brain controls involuntary actions such as heartbeat, salivation and vomiting.

Teacher's Note:
1. The medulla is a part of the hind brain.
2. Involuntary means without our will.

Answer: (d) Nervous and endocrine systems

Explanation:
1. Control and coordination in humans is done by the nervous system (electrical impulses) and the endocrine system (hormones).

Teacher's Note:
1. The two control systems work together.
2. Nervous control is fast; hormonal control is slow but long lasting.

Answer: (b) Pineal gland

Explanation:
1. The pineal gland in the brain secretes melatonin, which regulates sleep and wakefulness.

Teacher's Note:
1. Melatonin is the sleep hormone.
2. The pineal gland is a small gland inside the brain.

Answer: (d) Abscisic acid

Explanation:
1. Abscisic acid inhibits growth and induces dormancy of seeds and buds.

Teacher's Note:
1. Abscisic acid is the stress hormone.
2. Gibberellins break dormancy.

Answer: (c) synapse

Explanation:
1. The tiny gap between the axonal end of one neuron and the dendrite of the next is called a synapse.

Teacher's Note:
1. Chemicals cross the synapse.
2. A synapse is not part of a neuron.

Answer: (b) Neuron

Explanation:
1. Neuron or nerve cell is the structural and functional unit of the nervous system, while a nephron is the unit of the kidney.

Teacher's Note:
1. A neuron has dendrites, cyton and axon.
2. The nephron belongs to the excretory system.

Answer: (d) Control and coordination in human body depends only upon endocrine system.

Explanation:
1. Control and coordination in humans depends on both the nervous system and the endocrine system.
2. So the statement with the word 'only' is not true.

Teacher's Note:
1. Words like 'only' often make a statement false.
2. The other three statements are correct.

Answer: (a) slower than

Explanation:
1. Growth movements such as phototropism are slow, while movements due to turgor changes (like in day-night leaf movement) are faster.

Teacher's Note:
1. Growth movements need new cells, so they are slow.
2. Turgor movements are quick.

Answer: (b) cerebrum

Explanation:
1. The cerebrum is the largest part of the brain and has two cerebral hemispheres.

Teacher's Note:
1. Cerebrum is the thinking part.
2. Cranium is the bony box that protects the brain.

Answer: (b) Dendrite of sensory neuron

Explanation:
1. The olfactory receptors in the nose are the dendritic tips of sensory neurons, which first receive the scent.

Teacher's Note:
1. Information is always received by dendrites.
2. The sensory neuron carries it to the brain.

Answer: (a) folding-up of the leaves of Mimosa pudica.

Explanation:
1. Nastic movements are non-directional responses to a stimulus. Folding of Mimosa leaves on touch is nastic.
2. The other three are directional tropic movements.

Teacher's Note:
1. Nastic = not directed by the stimulus; tropic = directed.
2. Tendril coiling is thigmotropism.

Answer: (d) All the above

Explanation:
1. A tropic movement is a directional growth movement of a plant part, usually seen as curvature, in response to a stimulus coming from one direction.

Teacher's Note:
1. Tropic movement = directional and growth related.
2. Examples: phototropism, geotropism.

Answer: (a) Pons – Consciousness

Explanation:
1. The pons helps in regulating breathing; it is not the centre of consciousness.
2. The other three pairs are correct.

Teacher's Note:
1. The pons has a centre for regulating the breathing rhythm.
2. Cerebrum is the seat of memory and intelligence.

Answer: (c) Thyroxine

Explanation:
1. Thyroxine from the thyroid gland regulates carbohydrate, protein and fat metabolism.

Teacher's Note:
1. The gland is the thyroid; the hormone is thyroxine.
2. Do not confuse the gland with its hormone.

Answer: (b) Voluntary

Explanation:
1. Writing is done with our will, so the muscles used are voluntary muscles.

Teacher's Note:
1. Voluntary muscles are controlled by the brain.
2. Cardiac muscle works without our will.

Answer: (a) Auxins

Explanation:
1. Auxins make the cells of the stem elongate, which increases the height of the plant.
2. Cytokinins promote cell division and abscisic acid inhibits growth.

Teacher's Note:
1. Auxin means 'to grow' in Greek.
2. Gibberellins also help stem elongation, but auxin is the key hormone given in the source.

Answer: (d) Jumping from a height

Explanation:
1. Heartbeat, blinking and salivation are involuntary or reflex actions.
2. Jumping from a height is a voluntary action needing balance, which the cerebellum controls.

Teacher's Note:
1. Cerebellum: voluntary actions, posture and balance.
2. Medulla: involuntary actions.

Answer: (b) It regulates growth and development of the body

Explanation:
1. Insulin is made by the pancreas and lowers blood sugar level, and its deficiency causes diabetes.
2. Growth and development are regulated by growth hormone, so (b) is incorrect.

Teacher's Note:
1. Insulin works on blood sugar only.
2. Growth hormone comes from the pituitary gland.

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.

Explanation:
1. Chemicals are released at the axonal end, not at the dendritic end.
2. So statement (b) is incorrect.

Teacher's Note:
1. The axonal end releases chemicals; the dendritic end starts a new impulse.
2. Read the position of axonal and dendritic ends carefully.

Answer: (d) Insulin

Explanation:
1. Insulin helps cells absorb glucose and store it as glycogen, lowering blood sugar.

Teacher's Note:
1. Glucagon raises blood sugar.
2. Adrenaline also raises it in emergencies.

Answer: (b) amount of water

Explanation:
1. Plants do not have muscle proteins.
2. Plant cells change shape by taking in or losing water, which makes them swell or shrink and produces movement.

Teacher's Note:
1. Muscle cells use special proteins; plant cells use water.
2. Turgor changes explain the touch-me-not movement.

Answer: (b) Less amount of auxin in the region of contact

Explanation:
1. Auxin collects on the side of the tendril away from the support.
2. So the side in contact with the support has less auxin and grows less, and the tendril coils around the support.

Teacher's Note:
1. The side away from the support grows faster.
2. Auxin is the hormone involved.

Answer: (d) Abscisic acid

Explanation:
1. Auxins, gibberellins and cytokinins promote growth, whereas abscisic acid inhibits growth.

Teacher's Note:
1. Three hormones promote growth, one inhibits it.
2. Abscisic acid is the odd one out.

Answer: (b) cerebellum

Explanation:
1. The cerebellum of the hind brain controls posture and balance of the body.

Teacher's Note:
1. The cerebellum also makes voluntary movements precise.
2. A drunk person walks clumsily because the cerebellum is affected.

Answer: (b) Plant hormones are synthesized at places away from where they act and simply diffuse to the area of action.

Explanation:
1. Plant hormones are made in one part and diffuse to another part where they act.
2. Auxin goes to the shaded side, abscisic acid (not cytokinin) causes wilting, and electrical impulses travel rapidly.

Teacher's Note:
1. Auxin moves away from light.
2. Hormones act on target parts away from where they are made.

Answer: (d) Growth hormone

Explanation:
1. Insulin comes from the pancreas, oestrogen from the ovary and adrenaline from the adrenal gland.
2. Growth hormone is secreted by the pituitary.

Teacher's Note:
1. Pituitary: growth hormone and several trophic hormones.
2. Learn gland-hormone pairs.

Answer: (d) Regulates blood sugar level.

Explanation:
1. The thyroid gland is in the neck and makes thyroxine, which controls metabolic rate.
2. Blood sugar is regulated by the pancreas, so (d) is incorrect.

Teacher's Note:
1. Insulin from the pancreas regulates sugar level.
2. Thyroid needs iodine.

Answer: (d) Light and gravity

Explanation:
1. The stem grows towards light (positive phototropism) and against gravity (negative geotropism).
2. So the branches grow upright in response to light and gravity.

Teacher's Note:
1. Shoots show negative geotropism and positive phototropism.
2. Both stimuli act together here.

Answer: (b) Afferent

Explanation:
1. Nerves carrying impulses towards the CNS are sensory or afferent nerves.
2. Efferent (motor) nerves carry impulses away from the CNS.

Teacher's Note:
1. Afferent = arriving; efferent = exiting.
2. Afferent nerves are sensory.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Cytokinins promote cell division, and fruits and seeds are regions of rapid cell division.
2. Both statements are true and R explains why cytokinins are concentrated there.

Teacher's Note:
1. Cytokinins gather where cells divide rapidly.
2. Zeatin is a common cytokinin.

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. The release of hormones is regulated by feedback, so A is true.
2. Over and under secretion harm the body, so R is true, but it does not explain how the release is regulated.

Teacher's Note:
1. Feedback keeps hormones at the right level.
2. R states the importance, not the mechanism.

Answer: (b) Both A and R are true, but R is not the correct explanation of A.

Explanation:
1. Both statements are true.
2. However, the fact that the neuron is the unit of the nervous system does not explain what a synapse is.

Teacher's Note:
1. A synapse is the gap between two neurons.
2. Check whether R explains A.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Growth hormone promotes growth of the body and long bones.
2. So its deficiency in a child leads to dwarfism, and R explains A.

Teacher's Note:
1. Growth hormone is secreted by the pituitary.
2. Excess in childhood causes gigantism.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation:
1. Plants have no nervous system, but they coordinate their activities through plant hormones.
2. So both are true and R explains A.

Teacher's Note:
1. Plants coordinate through chemicals.
2. Animals use both nerves and hormones.