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Mechanisms of Speciation

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Suma Gondi

on 26 May 2011

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Transcript of Mechanisms of Speciation

Mechanisms of Speciation What is speciation? the formation of new species! caused by genetic changes (random mutations) The Two Causes of Speciation abrupt events
adaptation to different ecological niches cladogenesis splitting or diverging of a population into two or more species Two types of speciation: allopatric and sympatric allopatric speciation some members of a species occupy a habitat that is isolated from other members Where do you get random barriers from? land- mountain ranges
water- ocean, glaciers Another example of geographical isolation? when a small population moves to a new location that is geographically isolated from the main population such as a storm moving a population of birds new environment can cause natural selection, altering the genetic composition of the population adaptive radiation single ancestral species evolved into a wide array of descendent species that differ greatly in their habitat, form, or behavior hybrid zones area where two populations can interbreed Feature Investigation: Jeffrey Podos and Reproductive Isolation in Finches sympatric speciation members of species are within the same range diverge into two or more different species polyploidy organisms that have more than two sets of chromosomes plants tend to be more tolerant of changes caused by nondisjunction of chromosomes or interspecies breeding alloploidy organisms contain at least one set of chromosomes from two different species Interesting Facts! 40-70% of plants show polyploidy,while only 1% of animals do
those animals are mostly reptiles and amphibians Adaptation to local enironments Jeffrey Feder, Guy Bush, colleagues: N. American apple maggot fly- fed on native hawthorn trees, temporal isolation
Sara Via and colleagues- beginning of sympatric speciation in pea aphids, different hosts
metal tolerance in colonial bentgrass, change in flowering season, minimizes interbreeding in summation; Sexual Selection mate choice, diversifying mechanism- certain females prefer one pattern, others prefer another
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