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Chapter 22

Chapter 22. Descent with Modification: A Darwinian View of Life Part B: Evidence for Evolution. Recap main ideas of natural selection:. Evolution is change in species over time. There is overproduction of offspring, which leads to competition for resources.

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Chapter 22

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  1. Chapter 22 Descent with Modification: A Darwinian View of Life Part B: Evidence for Evolution

  2. Recap main ideas of natural selection: • Evolution is change in species over time. • There is overproduction of offspring, which leads to competition for resources. • Heritable variations exist within a population. • These variations can result in differential reproductive success. • Over generations, this can result in changes in the genetic composition of the population. Remember: Individuals do NOT evolve! Populations evolve.

  3. Evidence for Evolution: • Direct Observations • Fossil Record • Homology • Biogeography

  4. Evidence for Evolution

  5. Evidence for Evolution:1. Direct Observations Examples: • Insect populations become resistant to pesticides (DDT) • Methicillin-resistant Staphylococcus aureus (MRSA) • Peppered moth (pollution in city vs. country)

  6. The Rise of MRSA(methicillin-resistant Staphylococcus aureus)

  7. 2 points about Natural Selection • An editing process not a creative mechanism • A drug does not CREATE resistance, it SELECTS for it • It depends on TIME and PLACE • Favours characters that provide advantage in current, local environment

  8. Evidence for Evolution:2. Fossil Record • Fossils = remains or traces of organisms from past • Found in sedimentary rock • Paleontology: study of fossils • Show evolutionary changes that occur over time and origin of major new groups of organisms Ankle bones

  9. Prokaryotes (oldest fossils)  eukaryotes (fish – amphibians – reptiles – birds – mammals) • Transitional forms = links to modern species

  10. Evidence for Evolution:3. Homology • Homology: characteristics in related species can have underlying similarity even though functions may differ • Examples: • Homologous structures: similar anatomy from common ancestors (eg. forelimbs of human/cat/whale/bat) • Embryonic homologies: similar early development (eg. vertebrate embryos with tail & pharyngeal pouches) • Vestigial organs: structures w/little or no use (eg. flightless bird wings) • Molecular homologies: similar DNA and amino acid sequences

  11. Homologous Structures

  12. Embryonic Development

  13. Vestigial Structures

  14. Molecular Homologies • Compare DNA and amino acid sequences

  15. Evolutionary Tree

  16. Convergent Evolution • Distantly related species can resemble one another • Similar problem, similar solutions! • Analogous structures: similar structures, function in similar environments • Eg. Torpedo shape of shark, penguin, & dolphin

  17. Evidence for Evolution:4. Biogeography • Biogeography = geographic distribution of a species • Species in nearby geographic areas resemble each other • Continental drift and Pangaea explains similarities on different continents • Endemic species: found at a certain geographic location and nowhere else • Eg. Marine iguanas in the Galapagos

  18. Island Biogeography

  19. Galapagos Tortoises

  20. Tree of Life

  21. HHMI Short Film:Natural Selection & Adaptation Rock Pocket Mice Running Time: 10:25 min

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