Biol172_Chapter46_handout

Biol172_Chapter46_handout - Chapter 46 Animal Reproduction...

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1 Chapter 46 Animal Reproduction Both asexual and sexual reproduction occur in the animal kingdom Asexual reproduction is the creation of new individuals whose genes all come from one parent Essentially: clones Exception: parthenogenesis Sexual reproduction allows for the recombination of genetic material New recombinants may be better adapted in the environment Increased “fitness” Sexual Reproduction Sexual reproduction is the creation of offspring by the fusion of male and female gametes to form a zygote The female gamete is the egg The male gamete is the sperm Since the number of chromosomes doubles as a result of zygote formation a special type of cell division exists to reduce the chromosome number meiosis Gametogenesis Mechanisms of Asexual Reproduction Many invertebrates reproduce asexually by fission The separation of a The separation of a parent into two or more individuals of approximately the same size Nematostella vectensis
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2 Mechanisms of Asexual Reproduction Common in invertebrates is budding In which two new individuals arise from outgrowths of existing outgrowths of existing ones Hydra spec. Mechanisms of Asexual Reproduction Another type of asexual reproduction is fragmentation , which Is the breaking of the body into several pieces, some or all of which develop into complete adults Must be accompanied by regeneration • the re-growth of lost body parts Reproductive Cycles and Patterns Most animals exhibit cycles in reproductive activity Often related to changing seasons Reproduction is energetically demanding Successful outcome depends on available resources Successful outcome depends on available resources for the offspring Reproductive cycles Are controlled by hormones and environmental cues Reproductive Cycles and Patterns Animals may reproduce exclusively asexually or sexually Or they may alternate between the two Some animals reproduce by parthenogenesi Some animals reproduce by parthenogenesis A process in which an egg develops without being fertilized • The genetic makeup of the offspring differs from the parent because of meiosis! Parthenogenesis Parthenogenesis may be an adaptation of animals that colonize a habitat very rapidly Mating partner of the opposite sex may not be available Parthenogenesis may be seasonal
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3 Reproductive Cycles and Patterns Sexual reproduction presents a special problem for certain organisms That rarely encounter a mate One solution to this problem is hermaphroditism In which each individual has both male and female reproductive systems • Doubles the chances for a date!
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Biol172_Chapter46_handout - Chapter 46 Animal Reproduction...

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