Adaptation and Evolution

Adaptation and Evolution


  • Adaptation is a process by which organisms become better suited to their environment to increase chances of survival and reproduction.
  • This process occurs over generations, as random changes in the genetic material of a population accumulate and beneficial changes become prevalent.
  • These adaptations can be anatomical (related to bodily structure), physiological (related to bodily functions), or behavioural (related to the way an organism behaves).
  • It’s important to remember that individuals don’t adapt per se but rather, populations evolve over time as individuals possessing beneficial traits have a better chance to survive, reproduce, and pass on those traits.

Natural Selection

  • Natural selection is a key mechanism of evolution and involves differential survival and reproduction of individuals due to differences in phenotype.
  • This concept was first proposed by Charles Darwin and is often summarised as survival of the fittest.
  • Four key factors for natural selection are overproduction of offspring, genetic variation, struggle for existence, and differential survival and reproduction.
  • The result of natural selection is the adaptation of populations to their environment, leading to changes in the characteristics of species over time.


  • Evolution is the process by which different kinds of living organisms have developed and diversified from earlier forms during the history of the earth.
  • It is a gradual process, occurring over long periods of time, and may result in new species (speciation) due to accumulation of genetic changes.
  • Evidence for evolution includes the fossil record, which shows a progression of forms over time; the geographic distribution of species, which reflects the movement and adaptation of species; and homologies, or similarities in structures, which can indicate common ancestry.
  • Evolution drives biodiversity, as it gives rise to new species and thus increases the variety of life on Earth.


  • Speciation is the formation of new and distinct species in the course of evolution.
  • This process often occurs through allopatric speciation, whereby a population is divided by a geographic barrier (e.g. mountain, river), leading to genetic isolation and divergence over time.
  • It can also occur via sympatric speciation, where new species evolve from a single ancestral species while inhabiting the same geographic region.
  • Both forms of speciation contribute to biodiversity by increasing the number of species present in an ecosystem.

Genetic Drift

  • Genetic drift refers to changes in the allele frequencies of a population due to chance events.
  • This process can lead to the loss of genetic variation within populations.
  • Genetic drift often has a more significant effect on small populations, whereby chance events can make a big difference to the genetic makeup of a population.
  • Both genetic drift and natural selection drive evolution and biodiversity by changing the genetic makeup of populations and thus leading to new adaptations and speciation.