Evolution Why is it taught? Do you agree… ► Isthere variation within a species? ► Can new variations arise? ► Are there species on earth now that were not here long ago? ► Are there species there were here long ago that are not here now? ► Can a variation decrease survival chances? Do you agree? ► Can a variation increase survival chances? ► Are surviving individuals possibly more successful at reproducing healthy offspring? ► Can allele frequencies change in a population? Evolution ► Ifyou have agreed with the past eight statements, you agree that evolution occurs. ► Now let’s take a look… Why on Earth would anyone think of this kind of theory? ► Curiosity ► We share Earth with so many millions of other kinds of life. ► Human tendency (built into our wiring) to categorize or classify ► Consistent similarities in living things that are clearly different as well ► Darwin was intrigued with the diversity of life which clearly conflicted with popular theory about life on Earth. How does a hypothesis become a theory? Remember a hypothesis must be testable for support as well as being refuted. If the hypothesis continues to be supported with more scientists testing with modern and numerous observations and experiments, the hypothesis is seen as a theory of science. Isn't Evolution Just a Theory? II. A. Who was Charles Darwin? Strong desire to understand and explain what he could observe in nature. Naturally curious – true scientist Naturalist – main interests were studying nature and collecting a diversity of organisms. Recommended for position of naturalist on ship called the H.M.S. Beagle. By his professor at Cambridge. Reluctant rebel Darwin’s Observations Most important observations were on the Galapagos Islands off the coast of Ecuador. Saw similarities and differences among the organisms on mainland and the islands (600 mi. offshore). Became curious about origin of different plants and animals and variations of species he recorded of similar organisms. Finches and tortoises most often talked about in books, but he observed other animals and plants as well. Darwin’s observations Impressed with how organisms survived and produced offspring Realized importance of ancient organisms in solving puzzle of diversity – collected fossils. Noticed how well suited the species seemed to be for their environments. Darwin’s Analysis and Conclusions While on journey home he started making careful study of the specimens he collected, and thinking about the patterns he was seeing. When he got back to Britain, he took 20 years to carefully develop his theory of evolution. Published On the Origin of Species in 1859. III. Historical Look at the Theory of Evolution Influence on Darwin Maybe as Earth changes, so do forms of life. It would have to take a long time for life to change in the way he was inferring. Evolution became a revolutionary idea that was inspired by these & other controversial thinkers. Many people found his ideas too shocking to accept, and so did he. Lamarck (1809) Theory of acquired traits (transmutation) Need – If an organism needs a trait it will get the trait through extension of body. Use and Disuse – If an organism uses a trait it will remain; otherwise it disappears Inheriting acquired traits – Traits that the parents develop during their life will be passed to the children Not reasonable in today’s world Lamarck’s Evolution Theory Section 15-2 Acquired Traits Thomas Malthus (1798) Before the writings of Lamarck The Principles of Population essay stated populations outgrew their food supplies. This caused organisms to compete and struggle for one species to survive against another. Predicted humans would also outgrow their food supply and space on Earth. Note: Darwin read this essay. Alfred Russel Wallace Darwin was reluctant to publish his ideas due to the controversial nature of what he was thinking. Alfred Russel Wallace was a fellow naturalist who sent Darwin an essay on his own findings and theories about competition for resources (rings of Malthus) which were very similar to Darwin’s. This was the final push he needed to publish his own findings. What was Darwin thinking? He was always interested in using observations and prior knowledge (based on reading works of others) to formulate his inferences. He was not by nature a rebel and trouble maker. He was surprised and disturbed by his own observations He was not going to publish his work, but did want others to know of his findings. Beliefs of the time Not many people accepted the ideas of transmutation (evolution) stated by people like Lamarck. People believed in an Earth and life that were only thousands of years old. Everyone accepted the Earth and all life were as they were when created in one original creation event; no changes since then. When fossils kept popping up, some adjusted their beliefs to catastrophic events followed by periods of creation. Darwin’s argument People were really already using the idea of differences in individuals with selective breeding. Noted that breeders routinely used variation to improve crops and livestock, choosing individuals with desired traits to breed. Darwin’s term for this – artificial selection Evolution: Darwin – Theory of Natural Selection – All organisms produce more offspring than can survive – So, members of the species compete for food, space and survival (limited resources). – Within any population there is variation among the members – Organisms with the best variations for the environment in which they live will survive – Nature selects which organisms will survive – How Does Evolution Really Work Evolution / the controversial parts (descent with modifications) Species change over time. Species today have descended with modifications from species in the past. There is a single tree of life. Concept Map Section 15-3 Evidence of Evolution includes Geographic Similarities Homologous The fossil record distribution of in early body structures living species development which is composed of which indicates which implies which implies Physical Common remains of ancestral Similar genes Similar genes organisms species Evidence for Evolution Evolution = Change in species over time – Fossils – found in sedimentary rock / fossil record – Geographic Distribution – different animals on different continents, but similar animals in similar environments – Homologous parts – similar in basic internal structure but different form and function – Analogous parts – different body structure similar in function; usually in same environment Figure 15–14 Geographic Distribution of Living Species Section 15-3 Beaver Beaver NORTH Muskrat AMERICA Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara SOUTH Capybara AMERICA Coypu Figure 15– Section 15-3 15 Homologous Body Structures Turtle Alligator Bird Mammals Typical primitive fish Evidence (cont’d.) – Vestigial organs – body structure reduced in function (next slide) – Embryology – similar structures in embryos develop in same order – Genetic comparison – similar DNA and biochemistry Mechanisms for Evolution Populations evolve not single organism Populations change – Genetic equilibrium – frequency of alleles does change from generation to generation – Genetic drift – alteration of allelic frequencies by chance Geographic isolation – populations are isolated from other areas – island, mountains Reproductive isolation – formerly interbreeding organisms cannot produce fertile offspring Evolution of whale from land dwelling mammal.
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