Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Evolutionary (Darwinian) fitness is the measure of an organism's ability to survive and reproduce in its environment. It directly correlates with the number of viable offspring an individual contributes to the next generation.
5 Must Know Facts For Your Next Test
Evolutionary fitness is often measured by an individual's reproductive success.
Natural selection acts on individuals with higher evolutionary fitness, increasing their alleles in the population.
Fitness can be influenced by various factors such as genetics, behavior, and environmental conditions.
The concept of fitness includes both survival and reproduction, not just physical strength or health.
Relative fitness compares the reproductive success of different genotypes within a population.
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Related terms
Natural Selection: The process where organisms better adapted to their environment tend to survive and produce more offspring.
Genotype: The genetic constitution of an individual organism.
Adaptive Evolution: Changes in gene frequencies in a population due to selective pressures that increase overall fitness.