Chapter 22

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  1. Define Evolution
    • Darwin's Definition: Descent with modification 
    • -->The origin of species
    • population of species changes over time
    • ancesteral species differ from derived species
  2. Importance of Fossile Record
    • Shows life forms at different geologic times
    • --forms of life change over time
    • Sedementary rock layers form strata
    • Older layers deeper, ancesteral life forms
    • Newer layers near surface, derived life forms
  3. Adaptations
    • Characteristics that enhance survival and reproduction in specific environments
    • Populations adapt to their environment
    • --over generations
    • Example: Galapagos Island Finches (Break morphology of species differs, based on food available on their home island.)
  4. Evolutionary Trees
    • Can view history of life as a tree
    •   Ancesteral organisms at the base
    •   Derived organisms at the tips of the branches
    •   Some branches become extinct, others extant
  5. Artificial Selection
    • Mimics natural selection
    • Darwin saw this in farm animals and plants
    • Breeders can influence nature of offspring
    •   Affect outcome of next generation
    •   Over generations, population change
    • Agriculture plants and animals bear little resemblance to their wild ancestors.
  6. Darwin's Observations on Natural Selection
    • 1. Populations vary in their traits (individuals differ from one another).
    • 2. Traits are heritable (Traits passed from parents to offspring).
    • 3. Species can reproduce at high rates (more offspring than environment supports). 
    • 4. Not all offspring survive (due to a lack of resources).
  7. Effect of Natural Selection
    • 1. Individuals with favorable traits survive and reproduce at higher rates
    • 2. Populations of the organisms become adapted to their environment
    •    Over generations
    •    Accumulation of favorable traits
  8. Evidence for Natural Selection-- Direct observation
    Not always easy due to time scale
  9. Evidence of Natural Selection-- Fossil Record
    • Past organisms often differ from present day organisms
    • Gradual changes over short time periods (ex- Trilobite evol)
    • Significant changes over long time periods
    •      Whale evolution from land mammal
    •      Whales retain vestigial hind lmbs (Lost most original function through evolution)
  10. Evidence of Natural Selection-- Homology
    • Similarity resulting from common ancestry
    • Characters present in ancestors are often altered by natural selection. (adapted to different environments)
    • Ex. Forelimbs of mammals (Homologous structures)
    • Ex. DNA or protein similarity
    •      Molecular homology. 
  11. Evidence of Natural Selection-- Biogeography
    • Where species are/were found
    • Closely related species often evolved near to one another
    • May have become separated over time by movement of continents, formation of islands, or mountain ranges
    • Understanding past geography can help create an evolutionary tree.
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Chapter 22
2012-09-15 23:58:52

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