Chapter 46 notes

Parthenogensis chromosome duplicated and developed

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Unformatted text preview: gametes WITHOUT fertilization! Parthenogensis! Chromosome duplicated and developed into a 2N adult. Example:((In$2001,$a$hammerhead$shark$was$$ born$in$the$aquarium$of$the$Henry$Doorly$Zoo,$ Nebraska$$ •  Mother$had$not$been$in$contact$with$a$male$for$ 3$years$ •  In$2007,$gene8c$tes8ng$revealed$the$shark$was$ produced$via$parthenogenesis$ b/c no male DNA •  Hypothesis:$ was found. Chromosome of egg duplicated to make a 2N adult, OR an egg and polar body fused Sexual(Reproduc5on:((an$evolu8onary$enigma$ b/c its VERY COSTLY! Requires a lot of energy. And its gross Consider$an$animal$popula8on$where$half$the$females$reproduce$sexually$and$half$reproduce$asexually$ Number$of$offspring$per$female$is$2$ Genera8on$1$ Give$birth$to$$ Genera8on$2$ Give$birth$to$$ Give$birth$to$$ Give$birth$to$$ Genera8on$3$ Etc.$$ Etc.$$ Etc.$$ Etc.$$ Give$birth$to$$ Genera8on$4$ 8$females$capable$of$reproducing$asexually$ 1$females$capable$ of$reproducing$sexually$ O Which(strategy(of(reproduc5on(is(more(successful?((( bvi asexual…8 offspring vs. just 1 Why(( Increases in frequency with each generation….in SEXUAL reproduction, frequency stays the same S Which(strategy(of(reproduc5on(is(more(common(in(animals?((( exual reproduction mehhh Why?( The genetic variation in the offspring of SEXUAL reproduction is favorable….it enhances reproductive success, esp with environments change frequently! When they produce gametes & mate Reproduc5ve(cycles:((Oeen$8ed$to$changing$seasons$ $ $ REPRODUCTIVE TIMING IS VERY IMPORTANT……. Example:((Ewes$ Reproduc8ve$cycles$occurs$ during$fall$and$early$winter$ Gesta8on$8me$5$months$ ( When(are(lambs(born?( ( Around spring time (5 months after fall/winter) Why?( Offspring have greatest chance of survival in the spring bc they have food (grass) available to them In fall/winter signals reproductive cycle Voila Environmental$Cues$$$$$$$$$$$$$$$$$$$$$$$$$$$$Hormones$$$$$$$$$$$$$$...
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