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EVOLUTION UNIT 7A Part 1 of 2 DARWIN, NATURAL SELECTION, HARDY-WEINBERG Ch. 1 (p. 8-13) and Ch. 13 (all) • • • • • • • • • All life is connected. The basis for this kinship is evolution Evolution has transformed life on Earth from its earliest beginnings to its extensive diversity today Evolutionary view came into focus in 1859 with Darwin’s book Photo on left is Charles Darwin (1809-1882)(British biologist) with son William in 1842. One of Britain’s most renowned biologists Published The Origin of Species 17 years later. Was the the most influential scientist in the development of modern biology. Buried next to Isaac Newton in London’s Westminster Abbey. • 2 main points in book: • 1) species living today descended from ancestral species = “descent with modification” = evolution • Ex: the diversity of bears is based on different modifications of a common ancestor from which all bears descended. • 2) the mechanism for evolution is “natural selection” (see next slides) • • • Darwin loved nature. Disliked medical school. Became a minister. Became a naturalist for a voyage around the world when he was 22 years old. Darwin’s “Voyage of the HMS Beagle” is shown above. Observed and collected thousands of specimens. Observed adaptations of organisms. Most of animals of Galapagos Islands live nowhere else in world, but they resemble species living on the South American mainland. It was as though the animals strayed from mainland, then diversified as they adapted to environments on the different islands. • Darwin saw large diversity of animals on Galapagos Islands, off coast of South America • If an ocean separated islands, it isolated 2 populations of a single species. The populations could diverge more and more in appearance as each adapted to local environmental conditions. • After many generations, 2 populations could become dissimilar enough to be separate species - 14 species in the case of the birds called Galapagos finches. (This is now called divergent evolution) • They have beak shapes and colorations that are adapted to their environments • The beaks are adapted to certain food sources on the different islands; the colors protect them from predators • See next page for the finches!