Natural Selection
How Selection Works
The logic of natural selection
If individuals in a population vary, if some of that variation is inherited, and if certain traits help survival or reproduction, then those traits tend to become more common over time.
The three conditions
Variation + inheritance + differential reproductive success = natural selection.
Fitness
In biology, fitness means reproductive success, not physical strength. An organism with higher fitness leaves more surviving offspring in a given environment.
Natural selection in action
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Individuals in a population differ in traits.
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Some traits are heritable.
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Organisms with certain traits survive or reproduce better.
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Those traits become more common in the next generation.
In biology, what does fitness mean?
Fitness refers to reproductive success.
Correct answer: Leaving more offspring
List the three ingredients needed for natural selection.
These are the basic conditions under which selection can occur.
Correct answer: Variation, inheritance, and differential reproductive success.
If a trait is helpful but not heritable, what happens to it through natural selection?
Selection needs heritable variation to cause evolutionary change.
Correct answer: It cannot be favored by natural selection