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Evolution

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  1. Evolution Flora Biology I

  2. Evolution • Evolution – is a theory that describes the process by which modern organisms have descended from ancient organisms • “change over time” • Theory – well supported testable explanation of phenomena that have occurred in the natural world

  3. Charles Darwin • Contributed the most to our understanding of evolution • Voyage on the H.M.S Beagle in 1809 • Went ashore • Collected specimens • His observations • Plant and animal diversity • Ex: Galapagos Islands • Finches • tortoises

  4. Jean-Baptiste Lamark • First scientist to recognize: • Living things change over time • All species descended from other species • He concluded: • Organisms use or disuse body parts, organs, or traits over their lifetime • They pass these traits to their offspring • Ex: fiddler crabs

  5. Darwin’s Proposals • Artificial Selection – nature provides variations and humans select those variations that they find useful • Ex: largest hogs, cows that produce most milk, dogs. Etc. • Evolution by Natural Selection • Natural Selection – process by which organisms are better suited for their environment survive and reproduce most successfully. • Also called “survival of the fittest”

  6. Cont. Darwin’s Proposals • The ability of an animal to survive and reproduce is called fitness • Organisms with low levels of fitness usually die or leave few offspring • Fitness is the result of adaptations (any inherited characteristic that increases an organisms chance of survival • Porcupine quills • Spots on a deer • Coat changes in animals with season

  7. Descent with Modification • Descent with Modification – each living species has descended with changes from other species over time • Gives the idea that all organisms are related to each other

  8. Evidence for Evolution • Fossil record • Transitional fossils • Geographic Distribution • Different species of finches • Homologous Body Structures – structures that have different mature forms, but develop from the same embryonic tissue • Vestigial Organs • Body parts with no function • Ex: skink legs

  9. Summary of Darwin’s Theory • Individual organisms differ • Some of this variation is heritable • Organisms produce more offspring than can survive and reproduce • Because more organisms can reproduce than survive, they compete for resources • Individuals best suited for their environment survive and reproduce most successfully. • These organisms pass their traits to their offspring • This process of natural selection leads to changes in species over time

  10. Cont. Darwin Summary • Species alive today are descended with modification from ancestral species that lived in the distant past. • This process unites all organisms on Earth

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