3 What is “female” and “male”? • female has larger gametes (eggs larger, and less numerous, than sperm• female usually invests more resources in reproduction as compared to male• thus, female often is more ‘particular’ in selecting a mate
4 Eggs are more “expensive” than sperm. Sperm are very small (“inexpensive”)Eggs are large and nutrient rich (“expensive”).So, females INVEST more in gametes, and have more investment in each offspring compared to males;Asymmetry in sexual reproduction established…What effects does this have on mating behavior?
5 In general, success at mating: For a male, is limited by the number of femaleshe can convince to mate with him.For a female, is limited by the number of eggs/pregnanciesshe can produce.Leads to:Mate Competition (male-male, for access to females)Mate Choice (female choice, for best quality males)
6 Sexual selection is a subset of natural selection that has to do with mating success. If there is variation in a trait that affects ability to mate successfully, and that trait is heritable, then individuals with that trait will become more common over time.
8 Mate Selection and Competition Females MalesGreater investment in offspring • Less investment in offspringGenerate fewer offspring • Can generate more offspringChoosier in mate selection • Less discriminatingWait for best male • Maximize sexual opportunitiesMales = success objects • Females = sex objectsAttract males with: • Attract females with:Fertility, youth, fitness, beauty Wealth, power, status
10 NO testosterone FEMALE MALE XX XY ovary testis testosterone vas deferens, sex accessory glands1oviducts, uterus12clitoris, labia2penis, scrotumfeminine brain differentiationmasculine brain differentiation33