7.12 Variations in Populations

Diversity is protective

A population with high genetic diversity is more likely to survive change: some individuals may already carry alleles that help them cope with a new disease, climate, or predator. Populations with low genetic variation are more vulnerable to being wiped out by a single threat.

Where variation comes from

The ultimate source of new variation is mutation. Sexual reproduction shuffles existing alleles through recombination, creating new combinations. This variation is the raw material for natural selection — without it, a population can't adapt.

Key terms

Genetic variation

Differences in alleles among individuals in a population.

Diversity & resilience

High genetic diversity makes a population more able to survive change.

Low diversity risk

Populations with little variation are vulnerable to being wiped out by a single threat.

Sources of variation

Mutation (new alleles) and sexual reproduction (recombination of existing alleles).

Raw material for selection

Genetic variation is what natural selection acts upon.

Try an AP-style question

A population of genetically identical plants is exposed to a new fungal disease. What is the most likely outcome?

1. Some plants will survive because they vary in resistance
2. The entire population could be wiped out, because none are resistant
3. The disease will not affect a uniform population
4. The plants will develop resistance within their lifetimes