Reproduction, Heredity and Evolution
Reproduction explains how organisms produce offspring, including asexual and sexual modes, flower structure, pollination, fertilisation and human reproductive systems.
Core ideas
- Asexual reproduction produces genetically similar offspring from one parent: binary fission, budding, fragmentation, regeneration, spore formation and vegetative propagation.
- Sexual reproduction involves gametes and fertilisation, producing variation.
- A flower has sepals, petals, stamens (male) and carpels (female). The anther makes pollen; the ovary contains ovules.
- Pollination is transfer of pollen to the stigma; fertilisation is fusion of male and female gametes. These are not the same event.
- In humans, the sperm duct carries sperm; the oviduct carries the egg. The embryo implants in the uterus and develops into a foetus.
- Puberty brings reproductive maturity under hormones; the menstrual cycle prepares the uterus each month.
Worked example
After pollination, a pollen grain lands on the stigma and grows a pollen tube down the style into the ovule. The male gamete fuses with the egg inside the ovule. The ovule becomes the seed and the ovary becomes the fruit. Reasoning: pollination is only the transfer step; fertilisation is the fusion step that makes the zygote.
Traps that cost marks
Do not use pollination and fertilisation as synonyms. The ovary becomes fruit, not seed. In humans, the egg is released from the ovary and fertilisation normally occurs in the oviduct, not the uterus. Vegetative propagation is asexual despite involving plant parts.