Individuals don't adapt. Populations do.
- The idea
- Predict
- See it
- Why
- Check
The idea
“When the environment changes, each organism adapts and passes the change on to its offspring.”
We say animals adapt, and bodies do adjust, like muscles that grow with use. So it's easy to picture evolution as those adjustments getting passed down.
The short version
The mistake: When the environment changes, each organism adapts and passes the change on to its offspring.
What's actually true: Inherited traits don't change to fit a habitat. Individuals with helpful ones live and reproduce more, so the population changes.
- Evolution is a change in a population's allele frequencies over generations, meaning how common each version of a gene is.
- Natural selection needs a trait that already varies, affects survival or reproduction, and is inherited. The mice's fur color was all three.
- Selection acts on individuals, but only populations evolve. A tan or bigger muscles don't change the alleles in eggs or sperm, so offspring can't inherit them.
On the exam: Individuals survive or die. Populations evolve. Ask which individuals left more offspring.