Bio 201 F09 True lect 6 (L6)v2r

Bio 201 F09 True lect 6 (L6)v2r - todays factoid Shrinking...

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today’s factoid ‘Shrinking Sheep’ story in ‘Biology in the News’ on BB Sheep on Soay Island off the West Coast of Scotland have been getting smaller over several generations Normally in cold island habitats the average size would be expected to increase due to competition for scarce grass resources But due to milder winters (climage change) there is more grass and presumably less competition, so genetically smaller sheep can survive and leave offspring to the next generation
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clarification • on the “shelf life” of sperm • mature sperm – very short shelf life • sperm stem cells – much, much longer (but the more cell divisions; i.e. later in life, the greater risk of mutations being passed on
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Modes of Speciation Allopatric speciation geographical isolation Reproductive isolation as a “by product” Sympatric speciation – No geographic isolation – Two types of examples Polyploidy in plants • “instant speciation” Ecological • Divergent natural selection in same geographic region
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polyploidy
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Bio 201 F09 True lect 6 (L6)v2r - todays factoid Shrinking...

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