Question

(a) (i) Distinguish between hormonal co-ordination in plants and animals.
(ii) Which part of the brain is responsible for –
(1) intelligence
(2) riding a bicycle
(3) vomiting
(4) controlling hunger
(iii) How is brain and spinal-cord protected against mechanical injuries?
OR
(b) (i) What are tropic movements? Give an example of a plant hormone which (1) inhibits growth and (2) promotes cell division.
(ii) Explain directional movement of a tendril in pea plant in response to touch. Name the hormone responsible for this movement.

Answer 1

(a).(i)

(ii). (1) Intelligence: Cerebrum.
(2) Riding a bicycle: Cerebellum.
(3) Vomiting: Medulla oblongata.
(4) Controlling hunger: Hypothalamus.
(iii). The brain and spinal cord are protected by:
• Cranium and Vertebral Column: These bony structures provide physical protection.
• Meninges: These are three protective membranes surrounding the brain and spinal cord.
• Cerebrospinal Fluid (CSF): This fluid cushions the brain and spinal cord, absorbing mechanical shocks.
 

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(b). (i) Tropic movements are directional movements of plants in response to external stimuli. The direction of the response depends on the direction of the stimulus.
• Example: Phototropism (movement in response to light).
• Hormones:
– Inhibits growth: Abscisic acid (ABA).
– Promotes cell division: Cytokinin.
(ii) Explain directional movement of a tendril in pea plant in response to touch. Name the hormone responsible for this movement.
The directional movement of a tendril in pea plants is an example of thigmotropism (response to touch). When the tendril comes in contact with a support:
• Auxin accumulates on the side opposite to the contact.
• The cells on the opposite side elongate faster than the cells on the side in contact.
• This causes the tendril to curl around the support.
Hormone Responsible: Auxin.