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Evolution Natural Selection and Evidence of Evolution Charles Darwin Born February 12th, 1809 A naturalist, he studied all things of nature. Voyage of the H.M.S. Beagle Made observations and collected evidence towards THEORY of EVOLUTION Evolution: Darwin Darwin’s Theory: Natural Variation: Differences among individuals of a species Ex. Aquilegia flowers Artificial Selection: Nature provides variation among different organisms, humans select Ex. Largest hogs, fastest horses *Natural Selection favors traits that benefit organism in environment Environment does “selective breeding” Evolution: Darwin Fitness: ability to survive & reproduce in environment Adaptation: inherited characteristics that increases organisms chance for survival Survival of the Fittest (natural selection): Individuals better suited to environment, with high level of fitness, survive and reproduce successfully Natural Selection: struggle for existence. Evolution: Darwin vs.living Lamarck Species compete for food, space…etc. (mutations & genetic recombination lead to this) Don’t copy *Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness in its environment. Steps of Natural Selection • Variations within a population are raw material for natural selection Ex: giraffes with different necks lengths competing for food Next… • Living things face a constant struggle for existence and produce a lot more offspring than can survive Ex: Giraffes with longer necks reach leaves in tall trees Then… • Only some individuals survive and reproduce; best genetics produce offspring Ex: Giraffes with longer necks were better at getting food therefore had more offspring So… • Natural selection causes genetic change; in every generation the amount of individuals with better traits survive Ex: Over time long necked giraffes replaced short necked giraffes Finally we can say.. • Species adapt to their environment; selection tends to make the population more suited to its environment Ex: Longer necked giraffes are more successful and becomes the trait for a successful population Evolution: Darwin Descent with modification: species different from their ancestors; living species descended with changes from other species over time (GRADUALISM) Common Descent: all species were derived from common ancestors meaning a “single tree of life” Evidence for Evolution: Common Ancestors Evidence for evolution: Common Ancestor 1. Fossil Record: • Darwin believed living things evolved for Millions of yrs. • fossils provide evidence of Earth’s changing life Evidence for Evolution: Common Ancestor 2. Geographic Distribution of living things: Darwin’s finches were so similar, lived in different places, birds descended with modification from common ancestor Living on diff. continents, same ecological condition, similar pressures from natural selection ended up evolving common features Analogous Structures • Similar in function, different embryonic origins • Result of convergent evolution (similar environment) • Ex. Butterfly wing, dragonfly wing, bat wing, bird wing Evidence for Evolution: Common Ancestor 3. Homologous Body Structures: Similarities among bones of different organisms; different form and function; limbs adapted to different environments; common ancestor -Structures that originally functioned one way in ancestral species become modified as they take on new functions; proves evolution “remodeling process” Evidence that all four limbed animals with backbones descended with modifications from common ancestors. Create “trees” showing how recently last shared common ancestor WHALE HUMAN Bones develop from same cell in embryonic development BAT Evidence for Evolution: Common Ancestor 4. Vestigial Organs: No function; reduced in size; No affect on survival so natural selection doesn’t eliminate Vestigial Structures in Humans Evidence in Evolution: Common Ancestors 5. Similarities in early development: embryo of animals with backbones very similar. Embryonic cells develop in same order. Proves descent with modifications from common ancestor. Bird and human Evidence for Evolution: Common Ancestors Genetic Similarities • The closer related the organisms, the less the differences • Test DNA and protein sequences • Ex. Amino acids that differ in Hemoglobin of different organisms Natural Selection and Pesticides Evidence for Evolution: Common Ancestors