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Evolution

Explore the theory of evolution and natural selection, as proposed by Charles Darwin, and learn how organisms adapt and change over time. Discover the evidence supporting this theory, including the fossil record, transitional fossils, and homologous body structures. Gain a deeper understanding of how species evolve and how all organisms on Earth are interconnected.

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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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