Can you show a worked example?

Explain why more rabbits in a snowy area are white. White rabbits survive and breed more, so the trait spreads.

Natural selection

Individuals with helpful variations survive and pass them on.

Saying animals change on purpose because they need to (a giraffe stretching its neck).

Instead: Variation already exists. Those better suited survive and reproduce more, so their alleles become more common over generations.

Explain why more rabbits in a snowy area are white.

Sugar · Was there already variation in fur colour?
Student · Yes.
Sugar · Which rabbits are caught less?
Student · White ones.
Sugar · What happens over generations?
Student · White-fur alleles become more common.

Answer: White rabbits survive and breed more, so the trait spreads.

1. Do individuals evolve during their lifetime?
Show answer
No — populations change over generations
2. What is the original source of variation?
Show answer
Mutations (plus sexual reproduction)
3. Give a modern example.
Show answer
Antibiotic-resistant bacteria

What is the most common mistake with natural selection?: Saying animals change on purpose because they need to (a giraffe stretching its neck).
How do I get natural selection right?: Variation already exists. Those better suited survive and reproduce more, so their alleles become more common over generations.
Can you show a worked example?: Explain why more rabbits in a snowy area are white. White rabbits survive and breed more, so the trait spreads.

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