7The function of sexual recombination Increased variability—new combinations of alleles.Sexual populations better able to adapt to changing environment.(Group selection)
8Somatic cells and germ line cells Germ line cells give rise to the gametes.Gametogenesis (spermatogenesis & oogenesis)Oogenesis results in 3 polar bodies for each ovum.Somatic cells give rise to all the tissues of the body.
9Mechanisms of sex determination Y chromosomesIn humans, presence of Y induces male development.Ratio of X chromosomes to autosomesIn Drosophila flies, ratio of X chromosomes to autosomes determines whether male or female.TemperatureIn reptiles, temperature of nest often determines sex ratio of hatchlings.
10Levels of maternal physiological investment OviparyDevelopment takes place after female deposits egg.OvoviviparyDevelopment takes place within mother’s body, but without nutritional investment from mother.ViviparyDevelopment takes place within mother’s body, with nutritional investment from mother.Example: placental mammals