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Unformatted text preview: Animal Reproduction Chapter 46 Two Main Categories Asexual Reproduction Ex: Budding in Hydra Sexual Reproduction Ex: Copulation in Dogs Asexual Reproduction Common with Invertebrates Individuals are formed from genes coming from only one parent No fusion of eggs and sperm Advantages No need to find and convince a mate Offspring can be produced quickly Disadvantages Offspring are identical Asexual Reproduction Fission One parent separates into two or more approximately equal-sized individuals Ex: Single-celled organisms (protozoa) Budding New individuals split off from existing ones Ex: Hydra Gemmules Release of specialized cells that can grow into new individuals Ex: Sponges Fragmentation Breaking of the body into several pieces, some or all of which develop into complete adults Ex: Plants Parthenogenesis Development of an unfertilized egg into a completely new individual Offspring are clones of their mother Ex: Many invertebrates, some reptiles and fishes Sexual Reproduction Offspring are produced after the fusion of two haploid gametes Ovum (egg) from the female parent Usually large and non-motile Spermatozoan (sperm) from the male parent Usually small and highly motile Main advantage is that it increases genetic variation among offspring Disadvantage is that it can be much slower and more costly to find and convince a mate to cooperate Reproductive Strategies Very extensively among animals Animals may reproduce solely by asexual or sexual means Or, may use both strategies depending on environmental conditions Daphnia sp. (a freshwater crustacean) uses both sexual and asexual strategies that follow a complex life cycle Parthenogenesis is used after times of stressful conditions Sexual reproduction is used when environmental conditions are more favorable Hermaphroditism A form of sexual reproduction A hermaphrodite can function reproductively as a female or a male Many hermaphrodites can self-fertilize Most do not if it can be avoided Self-fertilization does not encourage genetic variation as much as out-crossing (mating with another individual) Often, each individual donates sperm and also recieves sperm during mating This is called...
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This note was uploaded on 03/27/2012 for the course BIO 1442 taught by Professor Britton during the Spring '11 term at University of Florida.
- Spring '11