Reproduction, Growth, Development and the Continuity of Life
What this domain tests
This section covers gamete formation, the human reproductive cycle, development and plant reproduction. You must be able to sequence the hormonal events and explain fertilisation and germination.
Human reproduction
- Meiosis in the testes and ovaries produces haploid gametes. Fertilisation normally occurs in the fallopian tube, not the uterus.
- Menstrual cycle: FSH stimulates follicle development; the follicle secretes oestrogen, which thickens the endometrium; an LH surge triggers ovulation around day 14; the corpus luteum secretes progesterone, maintaining the endometrium.
- Implantation follows fertilisation; the placenta exchanges nutrients, oxygen and waste and secretes hormones.
- If fertilisation does not occur, the corpus luteum degenerates, progesterone falls and menstruation follows.
Growth and development
- Growth is an increase in size or cell number; development involves differentiation of cells into specialised tissues.
- Plants grow from meristems throughout life; animals grow mainly to a fixed adult size.
Plant reproduction
- Flower structure: sepals, petals, stamens (anther, filament), carpel (stigma, style, ovary).
- Pollination transfers pollen; fertilisation follows pollen tube growth. Seed dispersal and dormancy aid survival; germination needs water, oxygen and a suitable temperature.
Worked example
If the LH surge is blocked, ovulation does not occur. Reasoning: LH triggers rupture of the mature follicle; without it no egg is released, progesterone from the corpus luteum never rises, and the endometrium cannot be maintained.
Traps
Saying fertilisation occurs in the uterus; swapping the roles of oestrogen and progesterone; claiming menstruation is triggered by rising oestrogen; forgetting that germination needs oxygen as well as water; confusing pollination with fertilisation.