BIOL 200B 1st Edition Lecture 19 Chapter 50 I. Passing on GenesII. Asexual vs. Sexual ReproductionIII. GametesIV. Internal and External FertilizationAnimal Reproduction2 ways to pass on genes:1. Asexual reproduction (by mitosis)- Budding- Fission- Parthenogenesis- Pros: fast, logistically simple, no energy expended finding mate, no need for males- Cons: genetic diversification, offspring are clones2. Sexual reproduction (meiosis, gamete fusion)- Pros: genetic variation- Cons: separate sexes, energy Many species regularly switch between asexual and sexual reproduction- spring – asexual reproduction by parthenogenesis (diploid female clones)- fall – sexual reproduction - switch to sexual reproduction only if exposed to crowded-poor quality water, low food availability, and short day length- genetically variable offspring have higher fitness in degraded, changing, or uncertain environmentsUltimate causation – addresses why a trait occurs in terms of its effect on fitnessProximate causation – addresses how a trait is producedThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Gamete Structure- sperm (race cars) – stripped down streamlined cells specialized for racing other sperm to eggo acrosome – enzyme filled pocket used for digesting jelly layer- egg – larger eggs filled with yolk (embryo food)o jelly layer – restricts sperm entryacrosome reaction – sperm digests jelly layer cortical granules – Ca2+ filled vesicles during fertilization Meeting of (correct) sperm and egg not simple - haploid sperm and egg fuse to form diploid zygote o sperm and egg must be same specieso must fuse only to each other, not other cellso only one sperm can fertilize an eggSexual reproductive variation in animals;1. External Fertilization (spawning) - Mostly aquatic animals - Large number of gametes- Broadcast to environment- Gamete release must be coordinated - Water temperature, day length, pheromones2. Internal Fertilization - All terrestrial and some aquatic animals- Benefit – fewer gametes required (especially costly eggs)- Requires either a spermatophore or penis and copulation - Snails fire “love darts”3 strategies for development 1. oviparity – egg laying, embryo develops in external environment2. ovoviparity – embryo develops inside mother’s body until ready3. viviparity – embryo develops solely inside motherConsequences - males compete for females- pre- and post-copulatory sexual selection - drives selection for male sexual traits- male/female ducks appear to be in evolutionary arms race ( corkscrew vagina and penis)- males grow/regress penis seasonally - competition among sperm to fertilize egg (post-copulatory selection)- competition between multiple males that have copulated with a female- sperm storage by female allows her to fertilize her eggs at a better timeEggs produced in ovaries- ovulation – egg expelled by ovary- enters oviduct (fallopian tube in mammals)- where fertilization occursEndocrine control of reproduction - puberty – transition to sexual maturity - menstrual cycle – female reproductive cycle in humans, expulsion of uterine lining, mammals have estrous cycle- gestation – developmental period inside