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Evolution: Why Are There So Many Living Things? Where Did the Idea of Evolution Come From? • Middle Ages: – “Ladder of Life” • Complex organisms found at highest rungs • Less complex at lower rungs • 1800’s – Georges Cuvier brought study of fossils to the level of science. Where Did the Idea of Evolution Come From? • Charles Lyell – Proposed theory of uniformitarianism. • Jean-Baptiste Lamarck – Published theory of the inheritance of acquired characteristics. Charles Darwin • Loved nature • Studied medicine – Struggled with the inhumane operating procedures • Switched to religion • Offered position as naturalist on British survey ship, The Beagle. Voyage around the World • Studied animals and fauna. • Noticed South American fossils differed from contemporaries. • Collected data for 27 years to support his mechanism for evolution. Fathers of Evolution • Alfred Wallace studied in Brazil and East Indies. • Developed mechanism of evolution independently of Darwin. • Sent a copy of it to Darwin. – Contained same conclusions as Darwin • Both presented their data at Linnaean Society of London in July 1858. How Did Darwin Account for Species? • In Origin of Species, he developed two main concepts – Evidence that evolutions has occurred. – Mechanism for evolution :natural selection. Major points of Darwin’s theories of evolution and natural selection • First observation: – Populations have the potential to increase exponentially. • Based on thoughts by Thomas Malthus Major points of Darwin’s theories of evolution and natural selection • Second observation: – Populations are fairly constant in size. Major points of Darwin’s theories of evolution and natural selection • Third observation: – Natural resources are limited. • Limited amount of space, nutrients, shelter • Results in competition for resources to survive. Major points of Darwin’s theories of evolution and natural selection • Deduction one: – Only some organisms survive. There is a struggle for existence among individuals in a population. • Organisms posses characteristics that enhance survival – Called adaptations. Three Types of Adaptations • Morphological-anatomical: modifications in form and structure that enhance survival. • Biochemical-physiological: modifications in the production and use of chemicals by organisms. • Behavioral Adaptations: Modifications in animal interactions with others and environment. Major points of Darwin’s theories of evolution and natural selection • Fourth observation: – There is variation within individuals of a population and variations are inherited. Major points of Darwin’s theories of evolution and natural selection • Deduction two: – Individuals with favorable variations are more likely to survive and reproduce. • Natural Selection: – “preservation of favorable variations and the rejection of injurious variations” Major points of Darwin’s theories of evolution and natural selection • Deduction three: – Accumulation of inheritable variation over many generations is evolution. • If changes within a species become great enough, a new species can result. What is a species? • Species are considered extinct if they do not interbreed in nature. – Implies offspring must also be able to reproduce. Evidence supporting Theory of Evolution • Selective breeding practices used by farmers result in: – “improved” domesticated plants and animals. • Darwin wondered if nature could do the same. Evidence supporting theory of evolution • Fossil record – Comparing fossils from ancestors with today’s species demonstrates species have evolved. Evidence supporting theory of evolution • Homologous structures – Structures dissimilar in form and function. • but share underlying structural similarities – Similarity due to a common ancestor?