Ant 15

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  1. Misconception about NS
    • - NS favors the survival of the species
    • - behavior is based on either nature or nuture
    • - culture triumps biology (or vice versa)
    • - evolution is progressive
    • - a biological explanation for a behavior that implies that is is justified
  2. what is Evolution?
    • - change over time
    • - in allele frequencies of a population from one generation to the next

    • Evolution:
    • Evolution allows us to explain relationships between living things. These resemblances are due to common descent from a shared ancestor.
  3. Natural Selection
    • 1. Tendency to overpopulate
    • 2. Individuals vary
    • 3. Variation passed onto offspring
  4. Postulate #1 Overpopulation
    • The ability of a population to expand is infinite, but the ability of an environment to support a population is always finite
    • Environment Constraints Population Growth:
    • ex. The Galapagos drought of 78'.
    • The drought affected seed availability (large, tuff).
    • Birds with beaks large enough to eat the seeds were most likely to survive.
    • Variation:
    • Organism's within populations vary, and this variation effects ability of organisms to survive and reproduce.
  5. Postulate #2 Variation
    • Individuals vary in ability to survive and reproduce
    • -beak size varied
    • -small beak birds were less efficient at eating the seeds
    • -larger beak depth in birds were more likely to survive
  6. Postulate #3 Inheritance
    • Variations are transmitted from parents to offspring
    • (beak size too?)
    • characteristics of population changed over time
    • -large beaked adults survived better
    • -large beaked birds had large beaked offspring
    • -mean beak size increased in population
  7. More on NS
    • The three conditions (Darwins Postulates in conjunction with the Galapagos drought) produce competition between organism for sutvival.
    • Organisms with advantageous raits pass them on
    • -adaptations
    • Leads to changes in a population

    • NS acts on Variation
    • -frequency of an allele will become more or less prevelant relative to other forms of the gene (pepper moth).
Card Set
Ant 15
Natural Selection
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