W1L1 Introduction to Evolution.pdf

1 disease health 2 harvesting of wildlife 3 food

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1. Disease & Health 2. Harvesting of wildlife 3. Food Production 4. Biodiversity 5. Human origins 6. Conservation 7. Joy of discovery Micro- vs. Macro-evolution Process and Pattern Microevolution: Changes in gene frequencies and trait distributions within and among populations. Typically refers to evolution within a species, and to the processes that cause evolutionary change over relatively short periods of time. Microevolutionary processes include natural selection, gene flow, random genetic changes across generations, and so forth Macroevolution: Generally refers to evolution above the species level, with a focus on large phenotypic changes or relatively long periods of time. Macroevolutionary topics include mass extinction, adaptive radiation, large-scale patterns in the fossil record, and so forth
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Course Trajectory Micro- evolution Macro- evolution Midterm Final 1st Lecture Midterm Synthetic subjects Macroevolution Where did whales come from? Fish-like - flukes generate thrust (no legs) - torpedo shaped body Mammal-like - tiny bones where hips should be - breath air via blowhole (no gills) - young drink milk - muscles run length of body Darwin (1859) hypothesized that whales evolved from a land-dwelling ancestor. Really? How did this happen?
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1979: Philip Gingerich discovers Pakicetus atrox - Found in rocks that formed on land (not in water) - Skull looks more like a dog than a whale 1979: Philip Gingerich discovers Pakicetus atrox - Found in rocks that formed on land (not in water) - Skull looks more like a dog than a whale - However, the bony wall around the middle ear (the auditory bulla ) has a hard lip of bone called an involucrum . Today the involucrum is only present in whales - Could Pakicetus be a whale ancestor? Auditory bulla with involucrum - Aquatic mammal - Rear feet shaped like paddles - Large tail (swam like an otter) - Long head (like an alligator) - Distinctive mammalian teeth (like Pakicetus ) - Bulla with involucrum - 48-50 myr old fossils Hans Thewissen Ambulocetus natans
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Ambulocetus natans Transitional Form: A species that exhibits traits shared by ancestral and derived groups, especially when the groups are sharply differentiated Evolution tinkers with existing structures to make new structures - front limbs flippers - genes for making limbs still exist in the genome (but aren’t functional; they are called pseudogenes) - gills did not evolve (blow hole moves to top of head) see also Fig. 4.32 The Whippo Hypothesis >30 fossil species have been found that illustrate the transition from a terrestrial mammal to an aquatic mammal DNA evidence suggests that
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