AP BIOLOGY

EVOLUTION

PATTERNS OF EVOLUTION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
If a plant is too short, it may not be able to compete with other (taller) plants for sunlight. However, extremely tall plants may be more susceptible to wind damage. Medium-height plants seem to not have either problem. What type of selection is most likely occurring?
A
directional selection
B
disruptive selection
C
stabilizing selection
Explanation: 

Detailed explanation-1: -When environmental pressures favor the average form of the trait, selection is said to be stabilizing. Directional selection occurs when selection pressures favor one extreme of the trait distribution. Selection is disruptive when the average form of the trait is selected against while either extreme is unaffected.

Detailed explanation-2: -Stabilizing Selection An example of this is plant height. In a population of plants, those that are short may not get enough sunlight, but those that are tall may be subjected to wind damage. This results in an increase in the number of medium-height plants and a decrease in very tall and very short plants.

Detailed explanation-3: -Stabilizing Selection–The extremes are selected against. Example: height; mostly beings tend to the average height-not too many really short ones or really tall ones. Directional selection–One extreme value is selected for. Example: speed; faster is always better so a population will tend to get faster over time.

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