Q1. [3] deep thorough-understanding
A fertilised egg implants in the uterine lining, which has become thick and richly supplied with blood. If the same uterine lining breaks down and is shed a few weeks later, what does this tell you about whether fertilisation occurred that month? Explain the mechanism behind what you observe.
Generated by claude-sonnet-4-6 · 2026-06-26 01:06 · grounding rag
Model Answer
The breakdown and shedding of the uterine lining tells us that fertilisation did not occur that month.
Mechanism: Every month, the uterus prepares itself by thickening its lining and richly supplying it with blood to nourish a potential embryo. If the egg is not fertilised, it lives for only about one day. Since no embryo implants, the thick spongy lining is no longer needed. It therefore breaks down and is shed through the vagina as blood and mucous — a process called menstruation, lasting about two to eight days.
Source: Chapter 7, Section 7.3.3(c) — What happens when the Egg is not Fertilised?
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Explanation
- The key link examiners expect: no fertilisation → no implanting embryo → lining not needed → menstruation.
- Always name the process (menstruation) for full marks.
- Avoid saying "fertilisation occurred" — the shedding is direct evidence it did not occur.
- The passage explicitly states the lining builds up for the embryo; its breakdown is the logical consequence of the embryo's absence. Connecting cause to consequence earns the reasoning mark.