Natural Selection and Adaptation
Big idea: Natural selection changes trait frequencies when heritable variation causes consistent differences in survival or reproduction, while adaptation describes a population-level fit to an environment.
Learning goals
- heritable variation
- fitness
- selection pressure
- adaptation
- trade-off
Core concepts
heritable variation
Differences among individuals that can be passed genetically to offspring.
fitness
Relative reproductive contribution of a genotype or phenotype to the next generation in a specified environment.
selection pressure
An environmental factor that causes phenotypes to differ in survival or reproduction.
adaptation
A heritable population trait shaped by selection because it improved fitness in past environments.
trade-off
An evolutionary compromise in which improving one function carries a cost to another.