Reproduction and Development
This domain examines how organisms reproduce, how gametes are formed, and how offspring develop. Questions compare sexual and asexual reproduction, interpret flower structure, and explain hormonal control of the menstrual cycle.
Reproduction types
Asexual reproduction uses mitosis and produces genetically identical clones. Sexual reproduction uses meiosis to form haploid gametes; fertilisation restores the diploid number and creates genetic variation.
Plants and humans
Flower parts: anther produces pollen; stigma receives pollen; ovary contains ovules. Pollination is pollen transfer; fertilisation is fusion of gametes. In humans, sperm and egg fuse in the oviduct. The embryo implants in the uterus and the placenta exchanges substances between fetal and maternal blood without mixing them. FSH, LH, oestrogen and progesterone control the menstrual cycle.
Worked example
A gardener self-pollinates a plant. Explain the offspring. Reasoning: self-pollination fuses gametes from the same plant, so the offspring are likely to be genetically similar and less varied. Cross-pollination brings different alleles together, increasing variation and possibly improving disease resistance.
Traps
- Pollination is not fertilisation.
- The placenta does not let maternal and fetal blood mix.
- Growth of the fetus is by mitosis, not meiosis.