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.
Types of Biological Adaptations with Examples
| Type | Definition | Example Organism | Adaptive Trait | Selective Pressure |
|---|---|---|---|---|
| Morphological | Structural body feature | Arctic fox | White winter fur | Predator avoidance on snow |
| Physiological | Internal biological process | Camel | Concentrated urine production | Water conservation in desert |
| Behavioural | Actions or responses | Monarch butterfly | Seasonal migration | Avoid winter cold |
| Molecular | Protein or enzyme change | Tibetan humans | EPAS1 gene variant | Low oxygen at high altitude |
| Coevolutionary | Adaptation to another species | Orchid and bee | Flower mimics female bee | Pollination without nectar cost |
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Related Terms
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.
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.
Convergent Evolution
Convergent evolution is the independent evolution of similar traits (analogous structures or functions) in unrelated or distantly related lineages, driven by similar environmental pressures or functional requirements rather than shared ancestry. It demonstrates that natural selection consistently favours certain solutions to ecological challenges, and it is important for understanding the difference between similarity due to common ancestry (homology) and similarity due to similar selection pressures (analogy). Classic examples include wings in birds, bats, and insects, and streamlined body shapes in dolphins and sharks.
From Latin "adaptatio", derived from "adaptare" (to fit to), composed of "ad-" (to) + "aptare" (to fit), from "aptus" (fit, suitable). In evolutionary biology, the term gained its modern meaning through the work of Darwin and was formalised in the early 20th century.