L25 Reproduction - Reproduction The purpose of life! Sex or...

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Reproduction The purpose of life!!
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Sex or no sex? Sexual reproduction maintains genetic variation within a population. Tunicates both asexual (budding) and sexual. Some vertebrate species are all female – PARTHENOGENESIS e.g. whip-tailed lizards, salamander, Amazon molly. MALE OR FEMALE? Sex determination in birds & mammals genetic at time of fertilisation – GENOTYPIC SEX DETERMINATION. Sex chromosomes – male mammals are the HETEROGAMETIC SEX, sperm are either X or Y. Female mammal eggs are only X. Birds – females are heterogametic sex – WZ, males ZZ Turtles, many lizards and gators – TEMPERATURE-DEPENDENT SEX DETERMINATION. >30oC female, <25oC males. How – estrogen overrides temp. Other reptiles that retain young in uterus have genotypic sex determination.
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HERMAPHRODITISM – evolves when genetic determination not present. Synchronous hermaphrodites – testis and ovaries function concurrently, or have OVOTESTIS – some teleosts, sea bass. Sequential hermaphrodites – many teleosts – first female then male PROTOGYNOUS; first male then female PROTANDROUS.
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male in each harem suppresses the tendency of the females to change sex by actively dominating them. Death of the male releases this
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This note was uploaded on 08/28/2011 for the course ZOO 3713c taught by Professor Staff during the Spring '08 term at University of Florida.

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L25 Reproduction - Reproduction The purpose of life! Sex or...

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