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Download 7.4 The Evidence for Evolution - Hutchison
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7.4 The Evidence for Evolution Pages 296-302 biogeography • The study of the distribution of organisms Galapagos Islands Darwin on the HMS Beagle • 1831-1836 • Galapagos Islands, 1000 km off the west coast of S. America • No large land mammals or amphibians • Strange reptiles, birds, insects and plants, similar to those found on nearest continent No fear!! • Birds land on your head. • Iguanas allow you to pick them up. • Sea lions sit beside you. loss of instinctive fear? Unique species • Arrived by water or air then changed into new species over time Comparing iguanas • Mainland iguanas have short claws for climbing trees. • Galapagos iguanas have long claws for hanging onto slippery rocks. Homologous Features • A structure with a common evolutionary origin currently used in different ways. Mammals • 7 neck bones Mammals • 28 skull bones Skeletons • Bat skeleton Human skeleton Homologous embryonic development • Human embryos have gill slits. Analogous Features • Body parts that perform the same function but do not share similar origin or structure fly eye rabbit eye Analogous features Dragon fly wing vs. bird wing Vestigial features Dew toes in dogs hip bones in whales Thomas Malthus The Principle of Population All populations were limited in size by their environment—and in particular their food supply.
