The theory of evolution is one of the most important concepts in biology. It explains how species change over time and how new species arise.

Evolution is based on the idea of variation, which refers to differences among individuals within a population. In this article, we will discuss the connection between the theory of evolution and variation.

Variation and Natural Selection

Variation is a key component of natural selection, which is the process by which organisms with advantageous traits are more likely to survive and reproduce than those without those traits. In other words, natural selection acts on the variation that already exists within a population.

Types of Variation

There are two main types of variation: genetic variation and environmental variation. Genetic variation refers to differences in DNA sequences among individuals in a population. Environmental variation refers to differences in environmental factors that can affect an organism’s phenotype (observable characteristics).

Sources of Genetic Variation

There are several sources of genetic variation, including mutation, gene flow, genetic drift, and recombination.

Mutation is a change in DNA sequence that can occur spontaneously or as a result of exposure to environmental factors such as radiation or chemicals.

Gene flow occurs when individuals migrate between populations and introduce new alleles (versions of genes) into that population.

Genetic drift occurs when random events cause certain alleles to become more or less common in a population over time.

Recombination occurs during meiosis (cell division that produces gametes) when homologous chromosomes exchange genetic material.

Environmental Variation

Environmental variation can also affect an organism’s phenotype. For example, temperature can affect the coloration of some reptiles, such as lizards. The availability of food can affect an organism’s size and shape.

The Role of Variation in Evolution

Variation is essential for evolution because it provides the raw material for natural selection to act upon. Without genetic and environmental variation, natural selection would have nothing to select from.

Adaptive Radiation

One important consequence of variation is adaptive radiation, which occurs when a single ancestral species gives rise to many new species that are adapted to different environments or niches. An example of adaptive radiation is the finches on the Galapagos Islands, which Darwin observed during his voyage on the HMS Beagle.


In conclusion, the theory of evolution is intimately connected to variation. Variation provides the raw material for natural selection to act upon and is essential for adaptive radiation and the origin of new species. Understanding variation is therefore crucial for understanding evolution and the diversity of life on Earth.