The phenomenon of bending of plant shoot towards a unilateral light source is due to:
A. Uniform distribution of auxin
B. Photolysis of chlorophyll
C. Differential distribution of auxin, with higher concentration on shaded side
D. Inhibition of growth by light
Answer: Option C
Solution (By JKSSB Mock Tests)
Phototropism (positive in shoots) is caused by the migration of auxin to the shaded side of the shoot, promoting cell elongation more on that side, causing the shoot to bend towards light. This asymmetric auxin distribution was demonstrated by Went's experiments. Auxin is sensitive to light and moves laterally. This is a growth response to directional light.
Explanation:
The epiglottis is a cartilaginous flap that covers the glottis (the opening into the larynx and trachea) during swallowing, directing food and liquid into the esophagus. The tongue moves food, the glottis is the opening itself, and the uvula is a soft tissue hanging at the back of the palate that assists in speech and prevents nasal regurgitation.
Assertion (A): Fishes are ammonotelic.
Reason (R): Ammonia is highly toxic and requires a large amount of water for excretion, which is available in aquatic environments.
A.A true, R false.
B.A false, R true.
C.Both A and R are true, and R is the correct explanation.
D.Both A and R are true, but R is not the correct explanation.
Explanation:
Ammonotelic organisms excrete ammonia directly into water, which dilutes it. This is feasible for fishes. The reason correctly explains why they are ammonotelic.
Explanation:
Active transport uses energy (usually ATP) to pump molecules or ions across a membrane against their electrochemical gradient, e.g., Na⁺/K⁺ pump. Diffusion, osmosis, and facilitated diffusion are passive processes that move substances down their gradient without energy expenditure.
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