which of the following features is not an adaptation?

Analyze the question: The question asks which feature is NOT an adaptation. The options seem to describe features of aquatic or water-living plants (hydrophytes), so we need to find the one that doesn't fit an aquatic habitat.

Concept: An adaptation is a structural, physiological, or behavioural feature that helps an organism survive in its environment. Aquatic and swampy plants have these adaptations:

• Breathing roots (pneumatophores) to take in air, since waterlogged mud has little oxygen.
• Flowers raised above water so insects and wind can pollinate them.
• Spongy tissue (aerenchyma) with air spaces to help them float.

Hairy leaves that reduce water loss are a feature of xerophytes (desert or dry-habitat plants). They trap a layer of moist air around the leaf and cut down transpiration.

Step-by-step evaluation:

• A. Breathing roots are an adaptation to waterlogged, oxygen-poor soil. ✔ Adaptation
• B. Flowers raised above water are an adaptation for pollination. ✔ Adaptation
• C. Spongy tissue holding gas gives buoyancy, an adaptation to floating in water. ✔ Adaptation
• D. Hairy leaves reduce water loss, which is useful in dry environments. For a plant in water, this makes no sense, because water is plentiful. In the context of this aquatic group, it is the odd one out.

Note on the question: Strictly speaking, hairy leaves ARE an adaptation for plants in dry habitats. The question is only sensible if the options are read as features of a water plant, where D does not apply.

Answer: D

Exam tip: When you see "which is NOT an adaptation" in a list, first find the habitat that most options point to (here, water). Then pick the option that belongs to a different habitat. Remember: hairy or waxy leaves = dry habitat (xerophyte); air spaces, breathing roots = water or swamp habitat.