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Biogeography - in different organisms are inherited from a...

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Biogeography: Separation and Divergence Biogeography is the study of the distribution of plants and animals throughout the world. Distribution of organisms is explained by related forms evolving in one locale and spreading to other accessible areas. Darwin observed South America had no rabbits; he concluded rabbits originated elsewhere. Biogeography explains why many finch species are on the Galápagos Islands but not mainland. Physical factors, such as the location of continents, determine where a population can spread. Cacti are restricted to North American deserts and euphorbia grow in African deserts. Marsupials arose when South America, Antarctica, and Australia were all joined; Australia separated before placental mammals arose, so only marsupials diversified in Australia. Comparative Anatomy: Similarities Due to Common Ancestry Organisms have anatomical similarities when they are closely related because of common descent, as substantiated by comparative anatomy. Homologous structures
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Unformatted text preview: in different organisms are inherited from a common ancestor. Vertebrate forelimbs contain the same sets of bones organized in similar ways, despite their dissimilar functions. Vestigial structures are remains of a structure that was functional in some ancestor but is no longer functional in the organism in question. Most birds have well-developed wings, although some birds have reduced wings and do not fly. Humans have a tail bone (the coccyx) but no tail. The presence of vestigial structures is explained by the common descent hypothesis. Embryological development reveals a unity of plan. During development, all vertebrates have a notochord and paired pharyngeal pouches. In fishes and amphibian larvae, the pouches become gills. In humans, first pair of pouches becomes a cavity of middle ear and auditory tube; second pair becomes tonsils, while third and fourth pairs become thymus and parathyroid glands. This makes sense only if fish are ancestral to other vertebrate groups....
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Biogeography - in different organisms are inherited from a...

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