Reproduction, Growth and Development
Sexual and asexual reproduction
Sexual reproduction involves gametes and fertilisation, producing variation; asexual reproduction produces genetically identical offspring from one parent. Know the human reproductive systems, gametes (sperm, egg), fertilisation, implantation and development of the fetus, including the placenta, umbilical cord and amniotic fluid. A frequent trap is mixing the roles of placenta (exchange of nutrients, oxygen and waste) with the umbilical cord (the connecting tube).
Plant reproduction
Flowers contain male parts (anther, filament) and female parts (stigma, style, ovary). Pollination transfers pollen; fertilisation follows. Seeds disperse by wind, water, animals or explosion. Learn the conditions for germination: water, oxygen and suitable temperature; light is not always needed, which is a common trap.
Growth and development
Growth is an increase in size and mass; development is an increase in complexity. Learn the stages of human development and the role of hormones such as oestrogen and testosterone. The menstrual cycle involves ovulation, thickening of the uterus lining and menstruation if no fertilisation occurs.
Worked example
A seed kept in a warm, dry place fails to germinate because water is missing; one kept in water but without oxygen also fails. Rule of thumb: all three conditions, water, oxygen and warmth, must be present together.
Practical trap
When comparing germination, change only one variable and keep others constant to make the test fair.