Reproduction, Growth and Development
What this domain tests
Reproduction, Growth and Development covers asexual and sexual reproduction, flower structure, pollination, seed formation and germination, human reproduction, the menstrual cycle, pregnancy, growth and development.
Core rules
- Asexual reproduction produces genetically identical offspring from one parent; sexual reproduction involves gametes and produces variation.
- Flower parts: sepals protect; petals attract pollinators; stamens, made of anther and filament, are male; carpels, made of stigma, style and ovary, are female.
- Pollination is transfer of pollen to the stigma. Fertilisation is fusion of male and female gametes. These are not the same event.
- After fertilisation, the ovule becomes the seed and the ovary becomes the fruit; the zygote becomes the embryo.
- Seeds germinate when water, oxygen and a suitable temperature are present; light is not required by all seeds.
- In humans, the placenta allows exchange of glucose, oxygen and waste between mother and fetus, but maternal and fetal blood do not mix.
- Growth involves increase in cell number and cell size; development is the differentiation of cells into specialised tissues and organs.
Worked example
A gardener crosses a red-flowered plant with a white-flowered plant and all offspring are pink. This suggests incomplete dominance: neither allele completely masks the other, and the heterozygote has an intermediate phenotype. If the offspring were all red, the red allele would be completely dominant. The reasoning depends on the phenotype ratios, not on the colours alone.
Traps
Do not say pollination is fertilisation. Do not claim the placenta mixes maternal and fetal blood. In the menstrual cycle, ovulation occurs around day 14 in a 28-day cycle; menstruation is breakdown of the uterine lining. Seeds do not need light to germinate, although seedlings need light to grow green.