Class 10 – Science Extra Questions – Ch. 6 – Control And Coordination

Ans: D

Explanation: The brain is the central control unit of the body. It is responsible for higher-level cognitive functions such as thinking, learning, and memory. It also controls essential involuntary functions like regulating heart rate and breathing. Furthermore, the cerebellum, a part of the brain, plays a crucial role in coordinating voluntary movements and maintaining balance. Therefore, the brain performs all the functions listed.
Correct Option: D

Ans: D

Explanation: Iodine deficiency can lead to an enlarged thyroid gland, a condition known as goitre. Adding iodine to salt, a process called iodization, is a public health measure to ensure people consume enough iodine and prevent goitre and other iodine deficiency disorders. Diabetes is related to blood sugar regulation, gonorrhoea is a sexually transmitted infection, and dysentery is an intestinal infection. None of these are directly prevented by adding iodine to salt.
Correct Option: D

Ans: C

Explanation: Sensory receptors are specialized to detect different types of stimuli. Photoreceptors are responsible for detecting light. Thermoreceptors detect temperature. Mechanoreceptors are sensitive to mechanical stimuli such as pressure, touch, and vibration. Chemoreceptors detect chemical stimuli, such as those related to taste and smell. Option A is incorrect because photoreceptors detect light, not sound vibrations. Option B is incorrect because thermoreceptors detect temperature, not light intensity. Option D is incorrect because chemoreceptors detect chemical stimuli, not temperature changes. Option C correctly pairs mechanoreceptors with their function of detecting pressure and touch.
Correct Option: C

Ans: C

Explanation: The seedling bends towards the light source, which is the burning candle. This directional growth in response to light is called phototropism. Chemotropism is a response to chemical stimuli, hydrotropism to water, and geotropism to gravity.
Correct Option: C

Ans: D

Explanation: Auxin is a plant hormone that plays a crucial role in phototropism, the process by which plants grow towards a light source. Light causes auxin to migrate to the shaded side of the stem, promoting cell elongation on that side and causing the stem to bend towards the light. Gibberellins are primarily involved in stem elongation and germination, cytokinins promote cell division, and eltroxin is not a recognized plant hormone.
Correct Option: D

Ans: A

Explanation: Gustatory receptors are specialized sensory cells located in the taste buds of the tongue and are responsible for the sense of taste. Olfactory receptors are located in the nasal cavity and are responsible for the sense of smell. Therefore, option A correctly describes the distinct functions of these two types of receptors. Options B, C, and D incorrectly attribute smell detection to gustatory receptors or taste detection to olfactory receptors, and option D also incorrectly links auditory receptors to smell.
Correct Option: A

Ans: A

Explanation: Cytokinins are a class of plant hormones that promote cell division and differentiation. They are primarily known for their role in promoting shoot formation and inhibiting root elongation. While cytokinins can influence lateral bud growth by interacting with auxins, their direct and primary stimulation is towards shoot development. Cork cambium formation is more strongly influenced by other hormones and environmental factors. Therefore, shoot formation is the most direct and significant process stimulated by cytokinin among the given options.
Correct Option: A

Ans: C

Explanation: Thyroxine, a hormone produced by the thyroid gland, plays a crucial role in regulating metabolism. The synthesis of thyroxine is dependent on the availability of iodine. Adrenaline is produced by the adrenal glands and is involved in the “fight-or-flight” response. Auxin is a plant hormone that regulates growth. Insulin is a hormone produced by the pancreas that regulates blood sugar levels. Therefore, only thyroxine requires iodine for its production.
Correct Option: C

Ans: C

Explanation: A reflex arc is the neural pathway that controls a reflex. It typically involves a sensory receptor, a sensory neuron, an integration center (often in the central nervous system like the spinal cord), a motor neuron, and an effector. Sensory neurons transmit signals from receptors towards the central nervous system. Motor neurons transmit signals away from the central nervous system to effectors (muscles or glands) which carry out the response. The integration center processes the information received from the sensory neuron and generates a signal sent via the motor neuron. Effectors are the structures that respond to the stimulus, not detect it. Option A is incorrect because sensory neurons transmit signals *to* the central nervous system, not from it. Option B is incorrect because motor neurons relay signals *to* effectors, not receptors. Option D is incorrect because effectors are the structures that respond, not detect stimuli. Option C accurately describes the role of the integration center.
Correct Option: C

Ans: A

Explanation: Photoperiodism is the physiological response of organisms to the length of day or night. The phenomenon was first scientifically described and named by American plant physiologists W. W. Garner and Harry A. Allard in 1920. While Borthwick was also a significant figure in photoperiodism research, Garner and Allard are credited with the initial discovery. Einstein is known for his work in physics, and Mendel for his foundational work in genetics.
Correct Option: A