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Evolution & Natural Selection

Change variation, selection pressure, and generations to watch a population shift.

Follow the mechanism1 / 3

Heritable variation exists. Individuals differ, and some differences can be passed to offspring; selection cannot act on a trait that is absent.

population changefavored trait rises ยท generation 8
Focus the idea
Natural selection changes trait frequency across generationsVariation is 65 percent, the trait advantage is 18, selection pressure is 70 percent, and the modeled trait frequency is 66 percent after 8 generations.12345678910trait frequency 66%each bar = a later generation
variation65%
advantage+18
trait frequency66%
pressure70%

Selection does not invent the trait; it changes how common an existing heritable difference becomes.

This is a population model. Individuals do not evolve because they need to; inherited variation and differential reproductive success change the next generation.

04 / PRACTICE

Make the biology yours.

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Answer from the model, then use the explanation to connect the visual mechanism to the biological rule.

CHECK 1 / 3

What does selection require to change a trait frequency?