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The Theory of Evolution

Charles Darwin and the Theory of Evolution. The Theory of Evolution. Darwin and the development of the theory. What is a SPECIES ?. Group of similar organisms Structurally biochemically Can interbreed successfully in nature Offspring are healthy Offspring are fertile (can reproduce).

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The Theory of Evolution

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  1. Charles Darwin and the Theory of Evolution The Theory of Evolution Darwin and the development of the theory

  2. What is a SPECIES? • Group of similar organisms • Structurally • biochemically • Can interbreed successfully in nature • Offspring are healthy • Offspring are fertile (can reproduce)

  3. Mule Liger These organisms are not new species…Why?

  4. Variation • Variation – differences between individual members of a population • Members of a species are very similar, but differences can be observed, or not, make each individual unique. • May be caused by mutations

  5. Mutations • Changes in DNA base sequences • Most are either neutral or harmful • Those that allow the organism to survive better in a particular environment are good and are more likely to be passed on to future generations.

  6. Most variations are not caused by mutations • Sexual reproduction combines genes from different parents • Crossing over during meiosis can produce variations

  7. Adaptation • An inherited trait that increases the population’s chances of survival and reproduction in a particular environment. • Allows organisms to fit best into a particular niche (habitat and role)

  8. Biodiversity • The variety and abundance of species that makes up a biological community. • Pine Barrens forests have little biodiversity – a limited number of species can survive there. • Tropical rain forests have great biodiversity – many species in a concentrated area.

  9. Organisms have changed over time to produce so many different forms of life

  10. Theories accepted before Darwin • 1769 – Bonnet – theorized that fossils were from animals/plants that lived before catastrophes that made them extinct.

  11. Jean Baptiste Lamarck • Use and disuse • Inheritance of acquired characteristics

  12. Darwin and his theory • Charles Darwin lived in early-mid 1800’s. • Went on voyage around the world as the ship’s naturalist – collected specimens of plants and animals during the 5+year-journey.

  13. Darwin’s Voyage

  14. Galapagos Islands Darwin’s route

  15. Darwin Returned Home to Think! • These influenced his development of the theory: • Evidence that the 13 different species of finches found in the Galapagos Islands were the descendents of one species. • HERE ARE JUST A FEW BEAK TYPES:

  16. Artificial selection – farm animals and plants

  17. Population control – population limited by resources and nature controls it by killing off some members during natural disasters, illness (epidemics), blights in plants, etc. • Geologic evidence of slow changes

  18. Darwin’s Theory of Evolution by Natural Selection • There is variation within a population • Some variations are good (helpful) • Not all young produced in a generation can survive • This leads to a struggle for existence. • Survival of the fittest. • Those that survive and reproduce are those with the good variations.

  19. Evidence supporting Evolution • Fossils – remains of plants or animals that lived before – can show structures

  20. Homologous Structures – similar in structure, but have different functions

  21. Vestigial Structures • Inherited • But, reduced in size and often not used. • Examples • Snake legs (they’re so reduced in size that they are not apparent). • Human appendix –no function, except can cause problems. • Human coccyx – tail bone.

  22. Analogous Structures • Similar in function, but very different in structure – indicate organisms are not closely related Insect wings Bat wing Bird wing

  23. Embryological Evidence • If organisms have similar embryos, they are more closely related than those with less similar embryos Sea lamprEy pond turtle chicken cat human

  24. Origin of Species • Speciation – evolution of one or more species from a single ancestor species. can be from: • isolation – usually because of a geographic barrier such as a canyon, mountain, or island

  25. Divergent Evolution • Isolated populations of a species evolve independently of each other. • Ex – polar bears and brown bears

  26. Convergent Evolution • Natural Selection produces analagous (similar) adaptations in different organisms in response to similar environments: • African Serval cat & south american maned wolf • See text p 242 • These animals have similar ears, legs, acute hearing, habitat, and Occupy similar niches

  27. Coevolution • Species that interact closely often adapt to one another:

  28. Adaptive Radiation • Many different species evolve from one ancestral species – each new species has a different niche

  29. Evolution Observed: Peppered Moths Less pollution More pollution Dark tree Light moths Dark moths Light tree

  30. The End

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