Healthy-looking doesn't mean genetically varied
- The idea
- Predict
- See it
- Why
- Check
The idea
“A population that looks big and healthy must have a lot of genetic variation.”
Healthy animals look like evolution's winners, so it's easy to assume their genes are rich too. Their condition says more about how well they're fed.
The short version
The mistake: A population that looks big and healthy must have a lot of genetic variation.
What's actually true: Genetic variation is how much individuals differ in their alleles, and a thriving population can have very little.
- Genetic variation is how much individuals differ in their alleles. You measure it in DNA, by counting the alleles at each gene.
- Size and health depend a lot on food. A population from a few founders can thrive and still carry only their few alleles.
- Natural selection can only work with variation that already exists. When conditions change, more alleles means a better chance that some work.
On the exam: Genetic variation lives in the DNA. Count the different alleles.