These ten questions mix sequence, structures, hormone data, inheritance and written explanation from human reproduction and development. They run from easier recall to harder reasoning. The data are invented for practice.
Write your answer first. Then open the worked answer and compare term, place and reason. The mistake log and retest queue is useful for recording errors.
Questions
Q1 (recall). Name the structure where fertilisation usually takes place.
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The oviduct. The zygote then travels towards the uterus while dividing.
Q2 (recall). State one function of the testis and one function of the sperm duct.
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The testis makes sperm (and testosterone). The sperm duct carries sperm towards the urethra.
Q3 (sequence). Put these in order: A, implantation. B, fertilisation. C, placenta develops. D, zygote divides by mitosis.
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B, D, A, C. Fertilisation makes the zygote, which divides into an embryo, which implants, and then the placenta develops.
Q4 (terms). Distinguish between a gamete and a zygote, including chromosome numbers in humans.
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A gamete is a sex cell, haploid with 23 chromosomes. A zygote is formed when two gametes fuse, and is diploid with 46 chromosomes.
Q5 (function). State one way the amniotic fluid helps the fetus.
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It cushions the fetus and protects it from knocks.
Q6 (explain). A student writes: “The baby’s blood and the mother’s blood mix in the placenta.” Correct this and give a reason.
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The bloods do not mix. Substances such as oxygen and glucose diffuse across a thin barrier between separate circulations. Mixing would expose fragile fetal capillaries to the mother’s higher blood pressure.
Q7 (data). The table is invented for practice.
| Day | Oestrogen (units) | Progesterone (units) |
|---|---|---|
| 1 | 10 | 1 |
| 7 | 30 | 1 |
| 13 | 90 | 2 |
| 21 | 50 | 40 |
| 28 | 10 | 2 |
(a) State the day of the highest oestrogen value. (b) Calculate the percentage increase in oestrogen from day 7 to day 13. (c) Explain the high progesterone on day 21.
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(a) Day 13 (90 units).
(b) Increase = 90 − 30 = 60. 60 ÷ 30 = 2, so 200%. Check: 30 × 3 = 90, a tripling.
(c) Progesterone maintains the lining of the uterus after ovulation, so it is high when the lining is being kept ready for a possible embryo.
Q8 (data, harder). Using the table in Q7, explain in terms of hormones why the uterus lining breaks down after day 21 if no embryo implants.
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After day 21 both hormones fall (progesterone from 40 to 2, oestrogen from 50 to 10 by day 28). With progesterone low, the lining is no longer maintained and breaks down (menstruation). In this model the pattern illustrates hormone roles, not any individual’s cycle.
Q9 (inheritance). Two parents are both Aa for a fictional recessive trait. (a) Give the probability a child is aa. (b) Give the probability that two children are both aa.
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(a) Gametes A and a from each parent give AA, Aa, Aa, aa, so 1/4.
(b) Births are independent, so 1/4 × 1/4 = 1/16.
Q10 (environment). In an invented study, mean birth mass was 3.3 kg in group P and 3.0 kg in group Q. (a) Calculate the difference as a percentage of group P. (b) State what conclusion is and is not justified.
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(a) Difference = 0.3 kg. 0.3 ÷ 3.3 = 0.0909, so about 9.1%.
(b) The data show an association: group Q had lower mean birth mass. They do not prove one factor alone is the cause, because other factors, including inherited ones, may differ between the groups.
If you got these wrong
- Wrong place or order (Q1, Q3): revisit the sequence lesson.
- Wrong structure or function (Q2, Q5, Q6): revisit explaining structures.
- Hormone data or percentage slips (Q7, Q8): revisit hormone-cycle data.
- Inheritance or association versus cause (Q9, Q10): revisit inherited and environmental influences. The inheritance model board lets you test another cross.
- Right idea, vague wording (Q4, Q6): revisit precise terminology.
If the hormone data or the explain questions keep costing you marks, a teacher in online one-to-one Biology tuition can go through your answers with you and find the pattern.