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Lecture14_slides_26Sep11

Lecture14_slides_26Sep11 - The Origin of Fossil record...

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1 The Origin of Evolutionary Novelty (or 150 years of “evo-devo”) Fossil record shows history of new groups sporting novel features backbone jaws limbs amniotic egg Origins of the novelties that characterize qualitatively new groups remains a fascinating challenge very active research with many breakthroughs in last 25 years What is novelty? Newly arisen character that differs more than quantitatively (Ernst Mayr 1960) Qualitatively new structure with discontinuous origin making a relatively abrupt deviation from ancestral characters (Muller 1990) What is novelty? Essence of definitions : qualitative not quantitative Archaeopteryx Ostrich Ground finch Novelties are often complex features with a big impact on lifestyle
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2 For example, 1 st vertz had no jaws! Filter feeders & sludge eaters Jaws are a BIG innovation! Sludge eaters biters, probers, pickers, suckers, crushers, chewers, plant eaters; ACTIVE lifestyle What is involved in the jawless to jawed transformation? 1 2 1 2 Complexity: jaws are more than a skeleton! muscles nerves Skeleton slits How does complex structural change happen under natural selection?
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3 Or as one 20 th century biologist put it: How do we get horses and tigers and things? …C. H. Waddington 1967 In part, the answer is in “selection thinking” Remember the 4 postulates: 1) Individuals are variable. 2) Variations are inherited (at least in part). 3) Some individuals reproduce more than others. 4) Success in reproduction is in part due to the variations.
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