Iodine is necessary for the synthesis of which hormone?
(a) Adrenaline
(b) Thyroxin
(c) Auxin
(d) Insulin
(b) Thyroxin
Which of the following is not associated with the growth of a plant?
(a) Auxin
(b) Gibberellins
(c) Cytokinins
(d) Abscisic acid
(d) Abscisic acid Abscisic acid inhibits plant growth; as a result, it is not related to plant growth.
The main function of abscisic acid in plants is to
(a) increase the length of cells
(b) promote cell division
(c) inhibit growth
(d) promote the growth of stem
(c) inhibit growth Explanation: The length of cells is increase by auxins. Cell division is promoted by cytokinins. Gibberellins promote stem growth.
The movement of shoot towards light is
(a) geotropism
(b) hydrotropism
(c) chemotropism
(d) phototropism
(d) phototropism Explanation The growth of plant roots towards or away from moisture is called hydrotropism. Plant growth in response to gravitational force is called geotropism. The growth of plants in response to a chemical stimulus is called chemotropism.
Posture and balance of the body is controlled by
(a) cerebrum
(b) cerebellum
(c) medulla
(d) pons
Ans is (b) cerebellum Explanation Processing of sensory information is done by the cerebrum. The medulla controls involuntary functions. Pons controls involuntary actions and sensations including touch and pain. It also regulates respiration.
Which of the following statements are true about the brain?
(i) The main thinking part of the brain is the hindbrain
(ii) Centres of hearing, smell, memory, sight etc are located in forebrain.
(iii) Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hindbrain
(iv) Cerebellum does not control the posture and balance of the body
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)
Ans is (c) (ii) and (iii) Explanation: The thinking part of the brain is the forebrain, hence statement I is incorrect. Because the cerebellum controls posture and balance, statement (iv) is wrong.
Which of the following statements are true?
(i) Sudden action in response to something in the environment is called reflex action
(ii) Sensory neurons carry signals from the spinal cord to muscles
(iii) Motor neurons carry signals from receptors to the spinal cord
(iv) The path through which signals are transmitted from a receptor to a muscle or a gland is called the reflex arc.(a) (i) and (ii)
(b) (i) and (iii)
(c) (i) and (iv)
(d) (i) , (ii) and (iii)
Answer ——(c) (i) and (iv) Explanation: Statements ii) and iv) are false since sensory neurons are responsible for transmitting signals from muscles to the spinal cord.
Which is the correct sequence of the components of a reflex arc?
(a) Receptors→ Muscles→ Sensory neuron→ Motor neuron→ Spinal cord
(b) Receptors→ Motor neuron → Spinal cord → Sensory neuron → Muscle
(c) Receptors → Spinal cord → Sensory neuron → Motor neuron → Muscle
(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle
Answer : (d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle Explanation: Receptors send impulses to sensory neurons. These impulses are sent to the spinal cord, and the motor neuron then relays them to the muscles.
In a neuron, conversion of electrical signal to a chemical signal occurs at/in
(a) cell body
(b) axonal end
(c) dendritic end
(d) axon
Answer is (b) axonal end Neurotransmitters are released at the axonal end in response to an electric impulse. To transmit the signal, these substances enter the dendrite of an additional neuron.