These eight questions mix the four skills so you choose the right approach each time. Write each answer before opening the explanation.
The lessons are in from biological recall to causal explanation. Log every lost mark in the mistake log and paper-error review.
Questions
1. A diagram shows a villus with a thin wall and a capillary network. Explain how it is suited to absorption. (3 marks)
Answer
The wall is one cell thick, so digested food diffuses a short distance. The capillaries carry food away, so the concentration gradient is kept steep. The finger-like shape gives a large surface area, so absorption is faster.
2. A cactus has spines instead of leaves. State the adaptation and explain its advantage. (2 marks)
Answer
The leaves are reduced to spines. The surface area for water loss is small, so less water is lost by transpiration in dry conditions.
3. Compare a red blood cell and a white blood cell on the presence of a nucleus, and explain the difference. (2 marks)
Answer
A red blood cell has no nucleus, whereas a white blood cell has one. The red blood cell has more space for haemoglobin, so it carries more oxygen, and the white blood cell needs a nucleus to make the proteins it uses to fight pathogens.
4. Explain how a plant loses water vapour through its leaves. Do not state only why this happens. (3 marks)
Answer
Water evaporates from the moist surface of mesophyll cells into the air spaces. The water vapour diffuses through the open stomata into the drier air outside. This movement down the concentration gradient is transpiration.
5. A student writes: “A polar bear has thick fur to survive.” Rewrite this to earn full marks. (2 marks)
Answer
The polar bear has thick fur that traps a layer of air, so heat loss to the cold surroundings is reduced and the body temperature is kept stable. The feature and the advantage are both stated, tied to the cold.
6. Explain how insulin lowers blood glucose after a meal. (3 marks)
Answer
Insulin is released by the pancreas when blood glucose is high. It makes the liver and muscle cells take up glucose and convert it to glycogen. The blood glucose level therefore falls back to normal.
7. Compare xylem and phloem on the substances they transport, and give a reason for the difference in function. (2 marks)
Answer
Xylem transports water and mineral ions from the roots to the leaves, whereas phloem transports sucrose made in the leaves to other parts of the plant. Xylem is made of dead, hollow vessels that let water flow freely, whereas phloem has living sieve tubes that carry sucrose. State both sides against the same criterion to earn both marks.
8. Decide whether this answer to “How does the heart pump blood?” is purpose or mechanism, then improve it: “To supply oxygen to the body.” (3 marks)
Answer
It is purpose. A mechanism answer says that the heart muscle contracts, which raises the pressure in the chambers, so blood is forced out through the arteries, and valves keep it flowing one way.
If you got these wrong
- Questions 1 and 4: open building a cause-process-effect chain.
- Questions 2 and 5: open separating an adaptation from the advantage it can provide.
- Questions 3 and 7: open explaining a comparison with the same criteria.
- Questions 6 and 8: open avoiding a purpose-only explanation.
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