Short answerModerate2 marks
Mention two adaptations in roots for absorption of water from the soil.
Topic: Root adaptations for absorption
Previous-year question practice database
Answer
Exam answer
- ROOT HAIRS — numerous unicellular outgrowths of the epidermis that vastly increase the SURFACE AREA available for absorption.
- THIN, PERMEABLE WALLS — the root hair wall is thin and its cell sap is more CONCENTRATED than the soil water, so water enters readily by osmosis. The roots also branch extensively and grow towards water (hydrotropism).
Explanation
Two adaptations, one mark each. For each, name the feature AND say what it achieves — the question says "for absorption", so the purpose is part of the answer.
The two strongest are SURFACE AREA and the OSMOTIC GRADIENT. They are different in kind: one is a matter of shape, the other of chemistry.
The general principle worth stating once, because it recurs throughout biology: wherever absorption or exchange happens, the structure is adapted to maximise SURFACE AREA and minimise THICKNESS. Root hairs, villi in the intestine, alveoli in the lungs and the gills of a fish are all the same idea.
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