CBSE Class 10 Biology Control and Coordination MCQs Set 05

Answer: (c) Phototropism

Explanation:
1. The shoot bends towards the source of light, which is the burning lamp, so this is phototropism.

Teacher's Note:
1. The stimulus here is light.
2. Light from any source works.

Answer: (b) Neurotransmitters and hormones

Explanation:
1. The nervous system coordinates through neurotransmitters released at synapses.
2. The endocrine system coordinates through hormones secreted into blood.

Teacher's Note:
1. The source option said circulatory system; it is corrected to endocrine system.
2. Nerves use chemicals at synapses; glands use hormones.

Answer: (c) stimulus is gained.

Explanation:
1. A nerve impulse is produced when a stimulus is received by a receptor.

Teacher's Note:
1. The stimulus comes first and the response follows.
2. The impulse links the two.

Answer: (d) axonal end of one neuron to dendritic end of another neuron.

Explanation:
1. A synapse is the gap between two neurons.
2. The chemical released at the axonal end of one neuron crosses the gap and starts a new impulse at the dendritic end of the next neuron.

Teacher's Note:
1. Transmission across a synapse is always in one direction.
2. Do not confuse the direction inside a neuron with that across a synapse.

Answer: (a) rapid relaying of nerve signals.

Explanation:
1. Neurotransmitters quickly carry nerve signals across synapses from one neuron to the next.

Teacher's Note:
1. Hormones give slow control; neurotransmitters give quick relaying.
2. They act between cells, not within one.

Answer: (c) Medulla oblongata

Explanation:
1. The medulla oblongata of the hind brain controls involuntary activities such as breathing rate and heartbeat.

Teacher's Note:
1. Cerebellum is for balance.
2. Medulla is for vital involuntary functions.

Answer: (c) Abscisic Acid

Explanation:
1. Abscisic acid closes the stomata, which reduces transpiration, so it acts as an anti-transpirant hormone.

Teacher's Note:
1. Abscisic acid is also the stress hormone.
2. Closed stomata reduce water loss.

Answer: (c) Pituitary

Explanation:
1. The pituitary controls the working of many other endocrine glands, so it is called the master gland.

Teacher's Note:
1. The pituitary lies at the base of the brain.
2. The hypothalamus controls the pituitary.

Answer: (d) Chewing

Explanation:
1. Vomiting, salivation and heartbeat occur without our will.
2. Chewing can be started and stopped at will, so it is voluntary.

Teacher's Note:
1. Involuntary actions are controlled by the medulla.
2. Ask whether you can control the action by choice.

Answer: (a) smelling

Explanation:
1. Olfactory receptors in the nose detect smell.

Teacher's Note:
1. Olfactory = smell; gustatory = taste.
2. Receptors are the sensory cells that detect stimuli.

Answer: (c) Piamater, Arachnoid and Duramater

Explanation:
1. The brain is covered by three meninges.
2. From inside outwards they are piamater, arachnoid and duramater.

Teacher's Note:
1. Piamater is in contact with the brain.
2. The meninges and cerebrospinal fluid protect the brain.

Answer: (b) growth regulators synthesised by plants and influencing physiological processes.

Explanation:
1. Phytohormones are chemical growth regulators made by plants that control their growth, development and responses.

Teacher's Note:
1. Phyto means plant.
2. Plant hormones are produced in small amounts.

Answer: (c) neuro-endocrine system

Explanation:
1. The nervous system and the endocrine system together coordinate the body, forming the neuro-endocrine system.

Teacher's Note:
1. Nerves and hormones work as a team.
2. The blood vascular system only transports.

Answer: (c) voluntary

Explanation:
1. Reflex actions are inborn, automatic, quick and protect the body.
2. They are involuntary, so they are not voluntary.

Teacher's Note:
1. Reflexes do not need conscious thinking.
2. They protect us from harm.

Answer: (d) Both (a) and (b)

Explanation:
1. Plant hormones are produced in very small amounts and are organic compounds, so (a) and (b) are not characteristics.
2. They can promote or inhibit growth, so (c) is a characteristic.

Teacher's Note:
1. Hormones act in tiny quantities.
2. Abscisic acid inhibits growth; auxin promotes it.

Answer: (d) Contact

Explanation:
1. Thigmotropism is the directional growth response of a plant part to contact or touch.

Teacher's Note:
1. Thigmo means touch.
2. Tendrils show thigmotropism.

Answer: (a) Tendrils

Explanation:
1. Tendrils of climbing plants such as pea show the response to contact most clearly.

Teacher's Note:
1. Tendrils coil around the support.
2. This helps plants to climb.

Answer: (b) Chemotropism

Explanation:
1. The stigma releases chemicals which guide the pollen tube only of the same species.
2. Growth in response to a chemical is chemotropism.

Teacher's Note:
1. Chemotropism guides the pollen tube towards the ovule.
2. Different species release different chemicals.

Answer: (a) diabetes

Explanation:
1. Diabetes patients do not make enough insulin, so insulin injections are given to control their blood sugar.

Teacher's Note:
1. Diabetes = lack of insulin.
2. Insulin is a protein, so it is injected and not taken as a tablet.

Answer: (a) a gland

Explanation:
1. An effector is the organ that responds to the stimulus, such as a muscle or a gland.
2. A light receptor is a receptor, and the brain and spinal cord are control centres.

Teacher's Note:
1. Effector = muscle or gland.
2. Receptor = detects the stimulus.

Answer: (a) dendritic tip

Explanation:
1. Dendritic tips receive information from receptors or other neurons.

Teacher's Note:
1. Dendrites receive, axons send.
2. Information becomes an electrical impulse in the neuron.

Answer: (a) Spinal cord

Explanation:
1. In a reflex arc the sensory neuron passes the signal to the spinal cord, which sends an immediate response through the motor neuron.

Teacher's Note:
1. Reflexes do not wait for the brain.
2. The spinal cord is the centre of most reflexes.

Answer: (d) P-(iii), Q-(iv), R-(i), S-(ii)

Explanation:
1. Olfactory receptors detect smell, thermoreceptors detect temperature, gustatory receptors detect taste and photoreceptors detect vision (light).
2. So P-(iii), Q-(iv), R-(i), S-(ii).

Teacher's Note:
1. Match the receptor name with its sense.
2. Photo = light, thermo = heat, gustatory = taste, olfactory = smell.

Answer: (b) Roots show negative phototropism whereas shoot shows positive phototropism.

Explanation:
1. Shoots bend towards light, which is positive phototropism.
2. Roots bend away from light, which is negative phototropism.

Teacher's Note:
1. Shoot: positive phototropism, negative geotropism.
2. Root: negative phototropism, positive geotropism.

Answer: (a) neurotransmitter

Explanation:
1. Acetylcholine is a chemical released at the axonal end of a neuron to carry the signal across the synapse, so it is a neurotransmitter.

Teacher's Note:
1. Neurotransmitters carry the signal across the synapse.
2. An impulse is electrical; acetylcholine is chemical.

Answer: (d) (I), (II) and (IV)

Explanation:
1. Hormones are secreted by endocrine glands, some glands are controlled by other hormones, and feedback controls many hormones.
2. Hormones are needed in very small quantities, so (III) is false.

Teacher's Note:
1. Hormones are effective in tiny amounts.
2. The pituitary hormones control other glands.

Answer: (d) Both (B) and (C)

Explanation:
1. The drooping of Mimosa leaves is a nastic movement that does not depend on growth.
2. It is caused by loss of water and turgidity in the cells at the base of the leaf.

Teacher's Note:
1. The movement is quick and reversible.
2. Both options (b) and (c) describe it.

Answer: (d) phototropism

Explanation:
1. Bending of the shoot towards light is a response to the light stimulus, so it is phototropism.

Teacher's Note:
1. The prefix photo means light.
2. Shoots are positively phototropic; roots are negatively phototropic.

Answer: (c) Testosterone from testes and estrogen from ovary.

Explanation:
1. Testes secrete testosterone in males and ovaries secrete oestrogen in females.
2. These hormones bring about the changes of puberty.

Teacher's Note:
1. Sex hormones are made by the gonads.
2. Match male with testes and female with ovary.

Answer: (d) A – Growth Hormone, B – Growth Hormone Releasing Factor, C – Insulin, D – Thyroxine

Explanation:
1. Growth hormone stimulates growth in all organs, and the growth hormone releasing factor makes the pituitary release it.
2. Insulin controls blood sugar and thyroxine regulates carbohydrate metabolism.

Teacher's Note:
1. Pair each function with its hormone.
2. The hypothalamus makes the releasing factor.

Answer: (b) chemotropism

Explanation:
1. The ovule releases chemicals that attract the pollen tube.
2. Growth in response to a chemical is chemotropism.

Teacher's Note:
1. Chemotropism means growth in response to chemicals.
2. The pollen tube grows towards the ovule during fertilisation.

Answer: (d) Cerebrum

Explanation:
1. The cerebrum, divided into two hemispheres, is the largest part of the human brain.

Teacher's Note:
1. It is the centre of thinking and memory.
2. The cerebellum is much smaller.

Answer: (c) Electrical impulse

Explanation:
1. At the dendritic tip the information starts a chemical reaction.
2. This reaction creates an electrical impulse that travels to the cell body.

Teacher's Note:
1. Dendrite tip: information to chemical reaction to electrical impulse.
2. The impulse then moves along the axon.

Answer: (c) A is true, but R is false.

Explanation:
1. Blinking is a reflex action, so A is true.
2. A reflex is spontaneous and involuntary, not voluntary, so R is false.

Teacher's Note:
1. Reflex actions are automatic and involuntary.
2. Source key given as (a) is corrected to (c).

Answer: (c) A is true, but R is false.

Explanation:
1. Ethylene is the gaseous hormone that hastens fruit ripening, so A is true.
2. Ethylene promotes, and does not delay, senescence of leaves, so R is false.

Teacher's Note:
1. Cytokinins delay senescence.
2. Ethylene ripens fruits.

Answer: (c) A is true, but R is false.

Explanation:
1. Insulin and glucagon together regulate blood sugar, so A is true.
2. Glucagon increases and insulin decreases blood sugar, so R is false.

Teacher's Note:
1. Insulin lowers blood sugar.
2. Glucagon raises blood sugar.

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

Explanation:
1. Adrenaline speeds up heartbeat and breathing and sends more blood to muscles in danger.
2. It prepares the body for fight or flight, so R explains A.

Teacher's Note:
1. Adrenaline is secreted by the adrenal glands.
2. It is also called the fight-or-flight hormone.

Answer: (c) A is true, but R is false.

Explanation:
1. Neurons carry messages all over the body, so A is true.
2. Acetylcholine is a neurotransmitter, not an inhibitor, so R is false.

Teacher's Note:
1. Acetylcholine is a chemical messenger released at synapses.
2. Be careful with technical terms in the reason.