Science (086) — AI-generated practice question

Touch-me-not (Mimosa): Cells change shape by changing the amount of water in them — water moves out of cells at the base of the leaf, causing them to shrink and the leaf to droop. No growth is involved.

Shoot bending towards light: Cells change shape by actually growing longer — the hormone auxin diffuses to the shady side, stimulating those cells to elongate more than the cells on the lit side, causing the shoot to bend towards light.

Why the difference in speed: The touch-me-not response involves only water movement in and out of cells, which happens almost instantaneously. The shoot's bending requires cell growth driven by auxin diffusion and elongation — a slower biological process — so it takes hours.

Source: Chapter 6, Sections 6.2, 6.2.1, 6.2.2

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• The key contrast examiners look for: water movement (turgor change) vs. cell elongation (growth) — make sure both mechanisms are named clearly.
• Link the speed difference directly to the mechanism: water movement is rapid; hormone diffusion + cell growth is slow. This cause-effect reasoning earns the 3rd mark.
• Avoid vague phrases like "the cells react differently" — be specific about how cells change shape in each case.