Reproduction and Development
What this domain tests
Questions cover asexual and vegetative methods with Kerala examples, flower structure, pollination and double fertilisation, human gametogenesis, the menstrual cycle, fertilisation, placenta and gestation.
Core rules
- Asexual: binary fission (Amoeba), budding (yeast, Hydra), fragmentation, spore formation (Rhizopus), and vegetative propagation - tapioca from stem cuttings, banana from suckers, ginger and turmeric from rhizomes, sweet potato from root tubers.
- Flower: calyx, corolla, androecium (anther and filament), gynoecium (stigma, style, ovary). Ovule holds the embryo sac.
- Pollination is self or cross, by wind, water, insects, birds or bats; fertilisation follows when the pollen tube enters the ovule through the micropyle.
- Double fertilisation in angiosperms: one male gamete fuses with the egg (2n zygote), the second with two polar nuclei (3n endosperm). Ovary → fruit; ovule → seed.
- Human: spermatogenesis in seminiferous tubules; a sperm carries 23 chromosomes; ovulation around day 14 of a 28-day cycle; fertilisation in the fallopian tube; implantation in the uterus; placenta exchanges nutrients, gases and wastes.
- Gestation about 280 days; oxytocin drives uterine contraction at birth.
Worked example
Coconut has 2n = 32. What ploidy and chromosome number does its endosperm show? Reasoning: endosperm forms from the fusion of one male gamete (n = 16) with two polar nuclei (each n = 16), so it is triploid: 3 × 16 = 48 chromosomes. The zygote, from gamete fusion, is diploid with 32.
Traps that cost marks
Saying double fertilisation occurs in all plants (angiosperms only); claiming the fruit develops from the ovule; putting fertilisation in the uterus; writing that the pollen tube enters through the style into the ovary cavity without naming the micropyle.