Reproduction: Plant and Human Reproductive Systems, Gametogenesis and Reproductive Health
Domain 7: Reproduction - what is tested
Questions cover flower structure and development, microsporogenesis and megasporogenesis, pollination and double fertilisation, the human male and female reproductive systems, spermatogenesis and oogenesis, the menstrual cycle, contraception and assisted reproduction.
Core rules
- Anther: microspore mother cells undergo meiosis to form microspores; each pollen grain is the male gametophyte and produces two male gametes.
- Ovule: megaspore mother cell forms four megaspores; usually one survives and forms the embryo sac with eight nuclei and seven cells. Double fertilisation gives a diploid zygote and triploid endosperm.
- Human male: testes produce sperm; sperm mature in the epididymis; semen contains sperm and seminal fluid.
- Human female: ovaries release ova; fertilisation normally occurs in the fallopian tube; implantation in the endometrium.
- Menstrual cycle: ovulation near day 14 of a 28-day cycle; LH surge triggers ovulation; corpus luteum secretes progesterone.
- Reproductive health: contraception, prevention of STIs, and ART such as IVF and IUI.
Worked example
A pollen grain lands on a compatible stigma. Explain the events up to fertilisation. The pollen tube grows through the style, guided by the synergids, and enters the ovule through the micropyle. It releases two male gametes into the embryo sac. One fuses with the egg to form the zygote; the other fuses with two polar nuclei to form triploid endosperm. Reasoning: this is double fertilisation, unique to angiosperms, and explains why the endosperm is triploid.
Traps
Calling the pollen grain the male gamete; saying endosperm is diploid; confusing ovulation with menstruation; placing fertilisation in the uterus; saying the corpus luteum secretes LH; treating contraception as abortion.