How It Works: How Natural Selection Drives Adaptation

How It Works: How Natural Selection Drives Adaptation

Adaptation is not a choice — it is the product of natural selection acting over many generations. Within any population, individuals show variation in their characteristics due to random mutations and sexual reproduction. Some of these variations make an organism better suited to its environment or better able to compete for limited resources such as food, water, light, or mates.

Individuals with beneficial variations survive longer and reproduce more successfully than those without. They pass the genetic basis of their favourable traits to their offspring. Over successive generations, the favourable variants become more common in the population because individuals carrying them leave more offspring. Over thousands of generations, this process produces organisms that appear exquisitely suited to their environment — what we call adaptations.

Intraspecific competition (between members of the same species) is the strongest driver of natural selection because individuals compete for exactly the same resources. Interspecific competition (between different species) is also significant when two species occupy a similar ecological niche. If competition is intense enough, one species will out-compete the other, leading to local extinction — a process called competitive exclusion. Adaptations that allow species to reduce overlap in their niches (e.g., feeding at different times or on different food sizes) allow them to coexist.