Reproduction, Growth and Development
What this domain tests
Reproduction in plants and humans, seed germination, the menstrual cycle, pregnancy and birth, growth measurement and development, including metamorphosis.
Core rules
- Pollination is the transfer of pollen to a stigma; fertilisation is the fusion of male and female gametes. Pollination does not guarantee fertilisation.
- A seed needs water, oxygen and a suitable temperature to germinate; light is not always required.
- In humans, FSH stimulates follicle development, oestrogen builds the uterine lining and triggers the LH surge, LH causes ovulation, and progesterone maintains the lining.
- The placenta allows exchange of glucose, oxygen, carbon dioxide and urea, but maternal and fetal blood do not mix.
- Growth is best measured as dry mass, because fresh mass fluctuates with water content.
Worked example
A maize seedling is grown in the dark. Its dry mass falls for the first week, then rises once leaves appear. Reasoning: in the dark the seedling cannot photosynthesise, so it respires its stored starch for energy, releasing carbon dioxide and water - mass is lost. Once the first leaves open and light is available, photosynthesis exceeds respiration and dry mass increases.
Traps that cost marks
- Using “pollination” when you mean fertilisation.
- Claiming the placenta is where maternal and fetal blood mix.
- Plotting fresh mass to compare growth rates.
- Forgetting that the LH surge triggers ovulation, not oestrogen.