Why do so many animals reproduce sexually rather than asexually?
(Figure 7.4) a. Sexual reproduction is more common among animals. b. The costs of sexual reproduction are greater. 1) It is more complicated, requires more time and uses more energy than asexual. 2) The cost of meiosis to the female is passage of only half of her genes to offspring. 3) Production of males reduces resources for females that could produce eggs. c. Sexual organisms produce more novel genotypes to survive in times of environmental change. d. Asexual organisms can have more offspring in a short time to colonize new environments. e. In crowded habitats, selection is intense and diversity prevents extinction. f. On a geological time scale, asexual lineages with less variation are prone to extinction. g. Many invertebrates with both sexual and asexual modes enjoy the advantages of both. 7.3. Reproductive Patterns A. Live-birth Versus Egg-bearing 1. Oviparous animals lay eggs in the environment for development. a. Fertilization may be internal (before eggs are laid) or external
