These eight original questions follow the lessons in plant adaptations. They ramp in difficulty and each answer shows the reasoning.
Write your answer first, then open the answer box.
The questions
Question 1. State how a thick waxy cuticle helps a xerophyte.
Answer
It reduces evaporation of water from the leaf surface, so less water is lost by transpiration.
Question 2. Explain why sunken stomata reduce water loss.
Answer
The pits trap humid air around the stomata. This reduces the difference in water vapour concentration between the leaf and the air, so less water vapour diffuses out.
Question 3. Why is water loss not a major problem for a water lily?
Answer
The plant is surrounded by water and its leaves float in humid conditions, so water is plentiful. A thick cuticle is not needed.
Question 4. State two functions of the large air spaces in a hydrophyte.
Answer
They make the plant buoyant so leaves float in the light. They also carry oxygen to submerged parts.
Question 5. Explain how aerial roots help a mangrove tree.
Answer
Mangrove mud is waterlogged and has little oxygen. Aerial roots stick up above the mud and have pores, so air reaches the roots for respiration.
Question 6. Give one way a halophyte can cope with the salt it takes in.
Answer
It can excrete salt through glands on its leaves. It can also store salt in old leaves that then fall off, so the salt leaves the plant.
Question 7. A plant has a cuticle of 3 µm, stomata on the upper surface only and 50% air space in the leaf. Name the plant type and explain one piece of evidence.
Answer
It is a hydrophyte with floating leaves. Evidence: 50% air space gives buoyancy and oxygen movement, and stomata on the upper surface exchange gases with air above the water.
Question 8. Plant M has a cuticle of 10 µm, 45 stomata per mm² in pits and a fleshy stem. Write a claim, evidence and reason.
Answer
Claim: M is a xerophyte. Evidence: a thick cuticle (10 µm), few stomata (45 per mm²) in pits, and a fleshy stem. Reason: the cuticle reduces evaporation, the pits trap humid air, and the fleshy stem stores water.
If you got these wrong
Questions 1 and 2 belong to relating xerophyte features to water conservation. Questions 3 and 4 belong to explaining hydrophyte adaptations.
Questions 5 and 6 need explaining halophyte adaptations, and questions 7 and 8 need comparing structures using environmental evidence. Log slips in the mistake log tool.
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