Ecology

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Author:
Anonymous
ID:
19115
Filename:
Ecology
Updated:
2010-05-12 22:08:48
Tags:
UK BIO INTRODUCTORY ECOLOGY
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  1. biodiversity
    • the distribution and abundance of life on earth, same thing as species diversity
    • Ecologists look for patterns seeking to explain this
  2. 3 kinds of Natural Selection
    • directional
    • stabilizing (normalizing)
    • disruptive
  3. Directional Selection
    • for one extreme and against other extreme
    • results in change in mean (average) phenotype
  4. Stabilizing (normalizing) Selection
    • favors the mean, against both extremes
    • keeps population phenotype distribution where it is
    • examples: many components of fitness; birth weights, egg #'s in bird nests
  5. David Lack and clutch size experiment in birds
    • egg # and egg survival trade off because of food limitation (quantity vs quality)
    • 1. average - medium egg #, pretty high survival, fledgling # high
    • 2. above average - high egg #, low survival, fledgling # medium, (too low quantity)
    • 3. below average - low egg #, high survival, fledgling # medium, (too low quality)
  6. Disruptive Selection
    • against mean, for both extremes (opposite of stabilizing)
    • end up with bimodal distribution, average may not change, but there will be two different bell shapes with different means
  7. Coho salmon
    • females build nests, males fertilize eggs, first two to get there fertilize the most
    • biggest male wards off other big males (hooknose) (largest mean)
    • small males hide nearby ready to sneak in (jack) the smallest is usually quickest and can sneak into tight places

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