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Evidence for Evolution Evidence of Evolution Essential Questions • What is the anatomical evidence of evolution? • How are fossils used as evidence of evolution? • What evolutionary evidence do we have from the field comparative embryology? • How does biogeography provide evidence for evolution? • How does genetics and biochemistry provide evidence for evolution? Evidence for Evolution • Scientists have found evidence for evolution in multiple disciplines – Anatomy, paleontology, comparative embryology, biochemistry, genetics, etc. Evidence for Evolution: Anatomy • Homologous structures: structural features with a common evolutionary origin Evidence for Evolution: Homology • Homology: similarity resulting from common ancestry • Homologous structures illustrate the structural similarities between seemingly unrelated species Homologous structure example: quadruped limbs -All creatures with four limbs have the same bone structure -This is true of mammals, birds, and reptiles The similarities in quadruped bone structure point to their descent from a common ancestor. It would have been impossible for these homologous structures to have arisen randomly in seemingly unrelated species. They must have shared a common ancestor. • How do we know that species with homologous structures are evolutionarily related? • Because we can compare homologous structures with analogous structures • Analogous structures: the body parts of organisms that do not have a common evolutionary origin but are similar in function • Analogous structures are examples of convergent evolution – Convergent evolution: the independent evolution of similar features in seemingly unrelated species • Analogous structures are examples of convergent evolution – Convergent evolution: the independent evolution of similar features in seemingly unrelated species (Analagous) Evolutionarily Related Evolutionarily UNrelated Further Anatomical Evidence for Evolution Vestigial structures: structures in a present day organism that no longer serves as its original purpose Vestigial structures illustrate that as species evolve over time, unused structures shrink and disappear Vestigial Structure Body part that has lost its original function through evolution Remainders of hind limb bones in whales suggest that at some point, this species no longer had a need for them. Evidence for Evolution: Fossils • Fossils provide a record of early life and evolutionary history Evidence for Evolution: Fossils • Most fossil plants and animals are found at specific time periods in the geological column. • No single fossil has ever been found out of order in this record of life on earth. Evidence for Evolution: Fossils • Fossil evidence can be used to put together a chronological history of a species’ evolution over time. Smithsonian Whale Evolution Evidence of Evolution: Embryology • Embryo: the earliest stage of development in plants and animals • Comparative embryology proves that the embryos of many species are extremely similar • Developing organisms look very similar to one another and often pass through developmental stages that resemble the organisms from which they evolved. Evidence of Evolution: Biogeography • Biogeography: the branch of biology that deals with the geographical distribution of plants and animals • Pangaea: the single large continent that existed 250 million years ago Evidence of Evolution: Biogeography • Isolated islands such as Madagascar are missing common species found on the mainland • The unique species they contain (like lemurs) evolved from a common ancestor into a new species due to geographical isolation – Endemic species: a species whose existence is restricted to a certain area Evidence for evolution: Adaptations • Structural adaptations have arisen over time – Mimicry: a structural adaptation that allows one species to resemble another species Adaptations like this show that over time, species can begin to resemble other species that are successful Evidence for evolution: Adaptations • Structural adaptations have arisen over time – Mimicry: a structural adaptation that allows one species to resemble another species – Camouflage: an adaptation that allows species to blend in with their environment Evidence for Evolution: Biochemistry • Genetics now provides evidence that all life on earth is linked, as all life on earth uses the same genetic molecules (DNA & RNA) • The more closely related the organisms, the more DNA they share Evidence for Evolution: Observation • Evolution of drug-resistant bacteria • Artificial selection: modification of species due to human selected breeding Evidence for Evolution: Observation • Evolution of drug-resistant bacteria • Artificial selection: modification of species due to human selected breeding Evidence of Evolution Evidence of Evolution Essential Questions • What is the anatomical evidence of evolution? • How are fossils used as evidence of evolution? • What evolutionary evidence do we have from the field comparative embryology? • How does biogeography provide evidence for evolution? • How does genetics and biochemistry provide evidence for evolution?