Physiological adaptation to very dry conditions in animal demonstrates

Analyze the question: The question asks which term describes a physiological adaptation of animals to very dry conditions.

Explain the concepts:

• Xeromorphism: structural (morphological) adaptations to dryness, such as thick cuticles, sunken stomata and reduced leaves. It is mostly used for plants (xerophytes), and it is a structural feature, not a physiological one.
• Hibernation: a state of inactivity during cold (winter) conditions.
• Aestivation: a state of dormancy or inactivity during hot, dry conditions. The animal slows its metabolism and conserves water until favourable conditions return. Examples: lungfish (which burrows into mud and secretes a mucus cocoon), snails and some amphibians.
• Rejuvenation: renewal or restoration of youthfulness or vigour. It has nothing to do with surviving dry conditions.

Solution:

1. The organism is an animal, so xeromorphism (a plant-structural term) does not fit.
2. The adaptation is physiological (a change in metabolism and activity), not structural.
3. The condition is very dry/hot, which points to aestivation rather than hibernation (cold).

So the answer is aestivation.

Answer: C. Aestivation

Tip: Remember the first letters:

• Aestivation = Aridity or Above-normal heat (summer)
• Hibernation = Harsh cold (winter)

A nice example for exams is the African lungfish (Protopterus), which aestivates in a mud burrow during the dry season.