A fertility nurse is helping a couple identify the days when an egg is most likely to be released. Fig. 1 is a record made by the woman over one menstrual c...
Question 1 Report
A fertility nurse is helping a couple identify the days when an egg is most likely to be released. Fig. 1 is a record made by the woman over one menstrual cycle. Her body temperature was measured immediately after waking each morning. A small rise in temperature can occur after ovulation. The woman’s cycle began on day 1, when menstrual bleeding started.
Fig. 1 shows the temperature record for the cycle.
(a) Describe the change in body temperature shown between day 13 and day 16. [2]
(b) Use Fig. 1 to state the most likely day of ovulation. [1]
(c) Explain why sexual intercourse close to this day gives the greatest chance of fertilisation. [3]
(d) Describe what happens to the lining of the uterus if the egg cell is not fertilised. [2]
(e) Explain why a fertilised egg must divide repeatedly before it can develop into an embryo. [2]
Answer Details
(a) The temperature rises from about \(36.4\,^{\circ}\text{C}\) to about \(36.8\,^{\circ}\text{C}\) between day 13 and day 16. This is a rise of about \(0.4\,^{\circ}\text{C}\). [2]
(b) Ovulation is most likely around day 14 or day 15, close to the temperature rise. [1]
(c) At ovulation, an egg cell is released. Sperm can travel to the oviduct, also called the fallopian tube, where fertilisation can occur. Because sperm survive for only a limited time, intercourse close to ovulation makes it more likely that sperm will be present when the egg is released. [3]
(d) If the egg is not fertilised, the lining of the uterus breaks down and leaves the body as menstrual blood. This is menstruation. [2]
(e) Repeated mitosis produces many cells. The cells can then grow and specialise to form the tissues and organs of the embryo. [2]
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