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Ch. 19 Darwin’s Decent with Modification

Ch. 19 Darwin’s Decent with Modification. Known today as Evolution. 2 Key Points of Natural Selection. # 1 NS is a editing process ….not a creative one. 2 Key P oints of Natural Selection. #2 NS depends on time a place. Evidence of Evolution. 1. Direct Observations 2. The Fossil Record

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Ch. 19 Darwin’s Decent with Modification

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  1. Ch. 19 Darwin’s Decent with Modification Known today asEvolution

  2. 2 Key Points of Natural Selection # 1 NS is a editing process ….not a creative one.

  3. 2 Key Points of Natural Selection #2 NS depends on time a place

  4. Evidence of Evolution 1. Direct Observations 2. The Fossil Record 3. Biogeography 4. Homology

  5. 1. Direct Observations • Insect population can rapidly become resistant to pesticides such as DDT. • Evolution of drug-resistant viruses and antibiotic bacteria.

  6. 2. The Fossil Record • Fossils provide evidence for evolution. • Fossils are remains or traces of organisms from the past. They are found in sedimentary rock. • Paleontology is the study of fossils. • Fossils show evolutionary changes have occurred over time and the origin of major or major new groups of organisms

  7. # 3 Biogeography: The geographic distribution of species • Species in a discrete geographic area tend to be more closely related to each other than to species in distant geographic areas.

  8. Example • In South America, desert animals are more closely related to local animals in other habitats than to the desert animals of Asia. • This reflects evolution, not creation

  9. Pangea

  10. # 3 Biogeography: • Continental Drift and the break-up of Pangea can explain the similarity of species on continents that are distant today. • Endemic Species are found at a certain geographic location and nowhere else.

  11. Ex. Marine iguanas are endemic to the Galapagos

  12. # 3 Biogeography: • Darwin’s theory of evolution through natural selection explains the succession of forms in the fossils record. Transitional fossils have been found that link ancient organism to modern species , just a Darwin’s theory predicts

  13. # 4 Homology Homology: Characteristics in related species can have an underlying similarity even though they have different functions. • Homologous structures • Embryonic homologies • Vestigial organs • Molecular homologies

  14. Homologous Structures • Forelimbs of mammals that are now used for a variety of purposes, such as flying in bats or swimming in whales. • Outwardly different yet same internal structure. • Shows common ancestry

  15. Homologous Structures are anatomical signs of evolution

  16. Embryonic Homologies • Comparison of early stages of animal development reveals many anatomical homologies in embryos that are not visible in the adult organisms. • Ex. All vertebrate embryos have a post anal tail and pharyngeal pouches

  17. Embryonic Homologiesaka comparative embryology

  18. Vestigial Organs • Are structures of marginal, if any importance to the organism. • They are remnants of structures that served important functions in the organisms ancestors.

  19. Vestigial Structures The Human Appendix

  20. Vestigial Structureshind legs in whales and snakes

  21. plicasemilunariaremnant of a 3rd eyelid (aka nicitating membrane)

  22. Nictitating membrane in owls

  23. Molecular Homologies • Are shared characteristics on the molecular level • Ex. All life-forms use the same genetic language of DNA and RNA. Amino Acid sequences coding for hemoglobin in primate species shows great similarity, thus indicating a common ancestor.

  24. In a comparision of chimpanzee and human genomes

  25. Convergent Evolution • Explains why distantly related species can resemble one another. • Convergent evolution has taken place when two organisms developed similarities as the adapted to similar environmental challenges- not because the evolved from a common ancestor.

  26. Convergent Evolution • The likenesses that result from convergent evolution are considered analogous. • Similar problem, similar solution

  27. Analogous Structurestorpedo shapes of a penguin, dolphin and shark

  28. What does that mean for Jupiter’s moon Europa?

  29. Organize your thoughts • Evolution is change in species over time. 2. There is overproduction of offspring which leads to competition for resources. 3. Heritable variations exists with in a population. 4. These variations can result in differential reproductive success. 5. Over generations, this can result in changes in the genetic composition of the population

  30. And Remember….. • IndividualsDO NOT evolve! Populations Evolve.

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