Reproduction
Core concepts
Distinguish asexual reproduction (binary fission, budding, fragmentation, vegetative propagation) from sexual reproduction (gamete fusion, genetic variation). Know gametogenesis: spermatogenesis and oogenesis, including meiosis and the unequal cytoplasmic division in oogenesis. Know the structure of the male and female reproductive systems and the roles of hormones (FSH, LH, testosterone, estrogen, progesterone). Understand the menstrual cycle phases and fertilization, cleavage, implantation. In plants, know flower structure (stamen, pistil), pollination, double fertilization in angiosperms, and seed and fruit formation.
Traps
Meiosis halves chromosome number; mitosis maintains it. Oogenesis produces one functional ovum and polar bodies; spermatogenesis produces four sperm. Double fertilization is unique to angiosperms (one sperm fertilizes the egg, one fuses with polar nuclei). Pollination is not fertilization. Asexual reproduction produces genetically identical offspring. Do not confuse the corpus luteum's role with the follicle's.
Worked example / rule of thumb
Rule of thumb: "meiosis makes variation; mitosis makes copies." Worked example: a diploid cell with 2n = 46 produces gametes with n = 23 chromosomes. In angiosperms, the pollen tube delivers two sperm; one fertilizes the egg (zygote, 2n) and one fuses with two polar nuclei (endosperm, 3n). If a question asks about genetic variation, point to crossing over and independent assortment in meiosis.