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). Brain Functions:
(1) Intelligence: Cerebrum.
(2) Riding a bicycle: Cerebellum.
(3) Vomiting reflex: Medulla oblongata.
(4) Hunger regulation: Hypothalamus.
(iii). Protective Structures of the Brain and Spinal Cord:
• Cranium and Vertebral Column: Bony enclosures providing physical protection.
• Meninges: Three membranes enclosing the central nervous system.
• Cerebrospinal Fluid (CSF): Fluid that cushions and absorbs shock.

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(b). (i) Plant Tropic Movements and Hormones: Tropic movements are directional plant growth responses to external stimuli, with the direction of growth dictated by the stimulus's direction.
• Example: Phototropism (growth towards or away from light).
• Hormones involved in plant growth:
– Growth inhibitor: Abscisic acid (ABA).
– Cell division promoter: Cytokinin.
(ii) Tendril Movement in Pea Plants: Explain the directional growth of a pea plant tendril in response to touch and identify the responsible hormone.
The directional movement of a tendril in pea plants, known as thigmotropism, occurs when the tendril contacts a support. This response is mediated by auxin:
• Auxin accumulates on the side of the tendril away from the support.
• Cells on the auxin-rich side elongate more rapidly than those on the contact side.
• This differential growth causes the tendril to coil around the support.
Hormone Responsible: Auxin.