Thursday, February 24, 2011

blog #4

Describe the three types of selection: directional, stabilizing and disruptive and give an example of each in your own words.


Stabilizing is when natural selection works against the two extremes of a trait to make the population more uniform. Stabilizing selection might work on the birth weighof human babies to keep them at an intermediate weight, because babies that are too big or too small have less chance of being born healthy.


Directional selection is a type of selection works to select the extreme of one trait. In a population of plants, flowers with the brightest color are selected for in order to attract the most pollinators.


Disruptive type of selection selects against the mean of the population.If there are two types of seeds to eat for a population of birds, either of two different beak shapes (sharp or blunt) might be selected for, but a beak that's the average of the two shapes might not be particularly good at eating either seed, so it would be selected against.
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