Chapter 14 Principles of Evolution I 14 1 How did Evolutionary thought evolve a Evolution is the change over time in the characteristics of a population not b Unifying theme for all biology c The foundation of evolutionary thought developed over centuries d The ideas of evolution were not accepted until after Darwin published On the Origin of e Early biological thought did not include the concept of evolution i Pre Darwinian all organisms were created simultaneously by God no change individuals Species in 1859 over time ii Plato 427 347 B C each object on Earth was merely a temporary reflection of its divinely inspired ideal form iii Aristotle 384 322 B C arranged all organisms on a linear scale of increasing complexity the ladder of Nature f Fossils showed that life has changed over time i Many of the fossilized species were extinct g A few scientists speculated that life had evolved h Different types of organisms had lived at different times in the past i This countered the view that species were created at one time and did not change i Older fossils are less similar to modern species than younger ones j Evolution has falsifiable predictions k No rabbits in the Cambrian period Why l A few scientists speculated that life had evolved i LeClerc Buffon 1707 1788 proposed that some modern species had evolved through natural processes having originated at creation from a small number of founding species ii Smith 1769 1839 a British surveyer recognized that certain fossils were always found in the same layers of rock 1 Concluded different types of organisms had lived at different times in the past iii Cuvier 1769 1832 proposed the theory of catastrophism 1 Catastrophes destroyed many species modern day species are the m Geology provided evidence that the Earth is exceedingly old survivors of these catastrophes i Hutton 1726 1797 Lyell 1797 1875 considered the forces of wind water earthquakes and volcanoes ii They developed the theory of uniformitarianism geologic change resulted from slow continuous actions similar to those at work today iii Rock formations reflect repeated cycles of geologic change occurring over vast periods of time 1 Floods lay down sediment which turns into sedimentary rock 2 Volcanoes periodically erupt laying down new layers of lava n Geology provided evidence that the Earth is exceedingly old continued i The geological evidence led to several conclusions 1 Earth 6 000 years old as proposed by theologians 2 Ample time for evolution to occur 3 Modern geologists estimate that the Earth is about 4 6 billion years old o Some pre Darwin biologists proposed mechanisms for evolution i Lamarck 1744 1829 proposed that organisms evolved through the inheritance of acquired characteristics 1 He theorized that organisms are modified during their lifetime through use or disuse of different parts 2 These modifications are passed to offspring ii This idea was incorrect acquired characteristics are not heritable p Darwin Wallace proposed a mechanism of evolution i By the mid 1880s evolution was popular but the mechanism was unclear this was the most important question of the era 1 Both traveled extensively studied plants animals 2 1858 Darwin and Wallace independently provided evidence of evolution and propose a mechanism how it occurs 3 Concluded species do change over time 4 Darwin published On the Origin of Species by Means of Natural Selection in 1859 II 14 2 How Does Natural Selection Work a Darwin and Wallace proposed that life s diverse forms arose through the process of descent with modification i Offspring differ slightly from their parents ii Over long time periods small differences accumulate to produce major transformations b Darwin and Wallace s theory rests on four postulates c Postulate 1 Variation in a population d Postulate 2 Some of the differences between members of a population are due to inherited characteristics not understood at the time though e Postulate 3 Differential survival and reproduction in each generation f Postulate 4 Individuals with advantageous traits survive longest and leave the most offspring a process known as natural selection remember an individual cannot evolve but a population can III 14 3 How do we Know That Evolution Has Occurred a Four main lines of evidence support evolution i Fossils provide evidence of evolutionary change over time 1 Fossils of ancient species tend to be simpler in form than modern species 2 Several series of fossils show the evolution of body structures over time a Suggest that new species evolved from and replaced previous species 3 Example modern whales evolved from land dwelling ancestors ii Comparative anatomy gives evidence of descent with modification 1 Comparing bodies of different species can reveal similarities suggesting shared ancestry 2 Homologous structures structures with the same evolutionary origin despite their current appearance or function result of divergent evolution a Example Bird and mammalian forelimbs b Similar anatomy structure but different uses 3 Analogous structures structures similar in appearance but differ in their evolutionary origin result of convergent evolution a Example Insect and bird wings b Different anatomy structure but similar uses 4 Vestigial structures remnants of structures that are inherited from ancestors provide evidence of evolution a Humans appendix tailbone wisdom teeth 5 Molar teeth in vampire bats which live off blood don t chew their food 6 Pelvic bones in whales and in certain snakes also serve no function in 7 modern species Idea as animals evolved into new habitats some of their structures that made them less fit were reduced to the point of insignificance iii Embryological similarity suggests common ancestry 1 All vertebrate embryos resemble one another in their early development 2 All vertebrate embryos possess genes that direct development of gill slits and a tail 3 Humans are born without gills a tail because the genes are active only 4 during early development Idea ancestral vertebrates possessed genes that directed the development of gills and tails and all their descendants still have those genes iv Modern biochemical and genetic analyses reveal relatedness among diverse organisms 1 All organisms share related biochemical processes a All cells use DNA as a genetic blueprint b All use RNA ribosomes and approximately the same genetic code for translation c All use the same 20 amino acids to build proteins d All use ATP to transfer energy e DNA
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