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Download Chapter 14 Principles of Evolution
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Evolution Chapter14 Observations Supporting Evolution • Evolution – process of change through time • Geological record – estimate that the earth is ~4.6 billion years old • Fossil – direct or indirect remains of organisms • Law of Superposition – in undisturbed strata, upper layers contain younger, more complex organisms. • Lower strata contain older, simpler life forms. Observations Supporting Evolution • Comparative Cytology – looks at similarities between cells and cell structures – Many organelles are structurally & functionally similar in most organisms • Comparative Biochemistry – similarities between compounds in living organisms • DNA, RNA, many proteins & enzymes – Example cytochrome C Observations Supporting Evolution • Comparative Anatomy – comparison of similarities between species • Homologous structures – anatomical parts w/ similar structure and origin, though they may work differently – Forelimbs of many different vertebrates • Analogous structures – similar function w/ different structures – Wings of birds & butterflies Comparative Anatomy • Analogous structures result from convergent evolution rather than descent from a common ancestor • Convergent evolution occurs when similar environmental pressures and natural selection give rise to similar (analogous) structures in distantly related organisms Observations Supporting Evolution • Comparative Embryology – similarities between early embryonic development – Early vertebrate embryos resemble one another – All vertebrate embryos possess genes that direct development of gill slits and a tail • Vestigial structures – non-functional in current organisms, functional in ancestors – Molar teeth in vampire bats, pelvic bones in whales Early Evolution • George Cuvier (1769-1832) – theory of Catastrophism. Modern species are the ones that survive • James Hutton (1726-1797) and Charles Lyell (1797-1875)– Uniformitarianism. Asserts that Earth is very old • Jean Baptiste Lamarck (1744-1829) – Use and Disuse, Transmission of Acquired Characteristics. • August Weismann – disproved Lamarck’s theory Darwin & Wallace • Both proposed similar theories on evolution at same time • Incorporated the ideas of Lyell • Darwin also incorporated the ideas of Thomas Malthus (Overproduction) • Proposed that species changed over time by natural selection Theory of Natural Selection • 5 major points: 2. Overproduction – more offspring produced than can survive 3. Competition – overproduction leads to competition for resources 4. Survival of the fittest – some members will have variations that make them better fit to survive Theory of Natural Selection 1. Reproduction – those that survive will reproduce passing on those variations 2. Speciation – over time this will lead to a new species • Darwin didn’t explain how variations arose (mutations) • Believed that both heredity & environmental variations were inherited Modern Theory of Evolution • Hugo De Vries – mutations a major source of variation • Modern theory supports Darwin’s concepts of variation & natural selection with genetic basis for variation • Mutations & sexual reproduction basis of genetic variation • Mutations are spontaneous. Raw material for evolution Modern Evidence of Evolution • Artificial selection is selective breeding to produce plants and animals that possess desirable traits – Modern dogs descended from wolves – In only a few thousand years, humans artificially selected for all breeds of modern dogs • Humans have created tremendous variation in several species over relatively short periods of time through artificial selection Natural Selection Today • Examples include: – Coloration in Trinidadian guppies – Pesticide resistance Coloration • Female guppies prefer to mate with brightly colored males; however, brightly colored males are more likely to be eaten by predators – Males found in areas lacking predators were brightly colored – Males found in areas with predators were duller by comparison (predators eliminated brightly colored males before they could reproduce) Pesticide Resistance • Numerous insect pests have evolved resistance to pesticides – Roaches developed resistance to Combat®, an insecticide bait that acted as an agent of natural selection – Resistant roaches possessed a rare mutation that caused them to dislike glucose, the main attractant in Combat® – At least one insect species is resistant to every pesticide in existence Natural Selection of Phenotypes • The variations on which natural selection works are produced by mutations that arise spontaneously 2. Natural selection selects for organisms that are best adapted to a particular environment – If the environment changes, a previously advantageous trait may become disadvantageous