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"Nothing in Biology makes sense except in the light of evolution." ~Theodosius Dobzhansky Evolution A scientific theory Subject to verification Explains observed phenomena based on observable scientific facts Continuously being tested as new evidence is found Evolution is change over time First theory of evolution proposed by Jean Baptiste de Lamarck (1744-1829) He hypothesized that similar species descended from a common ancester All living species were descended from similar extinct species evident in the fossil record To support his hypothesis, he used acquired traits Acquired trait-one that is not determined by genes-it arises during an organism's lifetime as a result of its experiences or behaviors He was the first to propose that species change over time Jean Baptiste de Lamarck and acquired traits THEN 50 years later… Charles Darwin and Alfred Wallace independently proposed the hypothesis that species were modified by natural selection Darwin Was 22 years old when he took a job as a naturalist aboard the H.M.S. Beagle The Beagle traveled to South America and the South Pacific on a five year voyage Darwin’s Voyage During that time, Darwin collected specimens and kept records of his observations He look at 13 similar but different species of finches on the Galapagos Islands On the islands, All the finches seemed to share a common ancester All had bill differences In 1858, Darwin Published his book The Origin of Species Darwin’s Theories: Descent with Modification: the newer forms in the fossil record are actually the modified descendants of older species all living things probably descended from one (or a few) common ancestors similar organisms arise in the same geographic locations Cont. Modification by Natural Selection: how evolution occurs natural selection-process by which organisms with favorable variations reproduce at higher rates than those without variations Fitness The ability to reproduce successfully The environment “selects” traits that will increase in a population Adaptation The ability of an organism to change in order to help the organism survive in a given environment Unfavorable traits gradually disappear because the organisms die out Factors that Affect Natural Selection Overproduction- producing more offspring than can possibly survive 2. Competition – food and resources are limited. (only the strongest survive) 3. Variations – slight differences among offspring 1. Organisms change over time through mutations and sexual reproduction