The mechanism of natural selection
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Question
Define natural selection.
Answer
The process where individuals with **advantageous heritable variations survive and reproduce more**, so the advantageous **allele becomes more common** over generations.
Question
What is the RESULT of natural selection?
Answer
A **change in allele frequency** in the **population** over generations — the helpful allele becomes more common and the population becomes better adapted.
Question
Does a single individual evolve during its lifetime?
Answer
**No** — an individual keeps the alleles it was born with. The **population** changes over generations, not the individual.
Question
What does 'survival of the fittest' actually mean?
Answer
Best able to **survive AND reproduce** — the individual that leaves the **most offspring**. Not necessarily the strongest or fastest.
Question
Why must the variation be heritable?
Answer
Only **allele-based** variation can be **passed to offspring**, so only it can change in frequency over generations.
Question
What is a selection pressure? Give examples.
Answer
An environmental factor that affects which variants survive — e.g. a **predator, disease, climate, or food shortage**.
Question
List the steps of the natural-selection mechanism.
Answer
Variation → overproduction/struggle → selection pressure → differential survival → differential reproduction → **allele frequency rises** over generations.
Question
Why does overproduction matter for natural selection?
Answer
More offspring are produced than can survive, creating a **struggle to survive** — so survival is unequal and selection can act.
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Topic 4.10 hub
Natural selection
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