Natural Selection
Natural selection is the process by which individuals with heritable traits that improve survival and reproduction in a given environment leave more offspring than those without such traits, causing those traits to become more common in the population over generations. It is the primary mechanism of adaptive evolution, first described by Charles Darwin and Alfred Russel Wallace in 1858. Natural selection acts on phenotypic variation and requires heritable differences in reproductive success to drive evolutionary change.
Four Requirements for Natural Selection
| Requirement | Description | Example | Without It |
|---|---|---|---|
| Variation | Individuals differ in traits | Coat colour in mice | No selection possible |
| Heritability | Traits passed to offspring | Beak shape in finches | Traits not transmitted |
| Differential Survival | Some variants survive better | Peppered moth camouflage | Equal survival rates |
| Differential Reproduction | Some variants reproduce more | Peacock tail attractiveness | Equal reproductive output |
| Abundance of Time | Many generations needed | Antibiotic resistance in bacteria | Detectable change unlikely |
Interactive Tools
Wikimedia Commons, CC BY-SA
Related Terms
Evolution (biology)
Biological evolution is the change in heritable characteristics of biological populations over successive generations, driven by mechanisms such as natural selection, genetic drift, gene flow, and mutation. It unifies all of biology by explaining the diversity of life on Earth through descent with modification from common ancestors. Evolution operates at multiple levels, from changes in allele frequencies within populations (microevolution) to the origin of new species and higher taxa (macroevolution).
Evolutionary Fitness
Evolutionary fitness is a measure of an organism's reproductive success relative to other individuals in the population, quantified as the average number of offspring that survive to reproductive age. It is not a measure of physical strength but of how well an organism's genotype is represented in the next generation. Absolute fitness is the actual number of reproducing offspring, while relative fitness normalises this value against the most successful genotype in the population.
Adaptation (evolution)
An adaptation is a heritable trait that increases an organism's reproductive fitness in its environment, shaped by natural selection over many generations. Adaptations can be morphological (structural), physiological (functional), or behavioural, and they arise because individuals carrying the trait leave more offspring than those without it. The concept of adaptation is central to evolutionary biology and explains the remarkable fit between organisms and their environments.
From Latin "naturalis" (of nature) and Latin "selectio" (a choosing, from "seligere" to pick out). The term was coined by Charles Darwin in his 1859 work "On the Origin of Species by Means of Natural Selection".