Mutations are permanent changes in the DNA sequence of a gene, and is the source of new alleles in a population's gene pool. A mutation has the ability to change one allele into another, the net effect being a change in the frequency of the existing allele. Mutations' effect on allele frequencies is usually insignificant, unless it provides a beneficial trait to an organism in regard to selection pressures in the environment. A selection pressure is an abiotic or biotic environmental factor which enhances the survival and reproduction of those individuals who possess a beneficial trait in coping with the pressure, or it reduces the survival and reproduction of individuals lacking the trait. Selection pressures can contribute to changes in allele frequencies in a population's gene pool and therefore also drive natural selection. When individuals with particular alleles which are better suited to survive certain selection pressures reproduce and pass on the advantageous alleles, this is known as the phrase "survival of the fittest". There are three types of mutations which are considered in evolution.

• Harmful mutations

• Neutral mutations

• Beneficial mutations
  

  1. Harmful mutations are removed from the population by selection and will generally only be found in very low frequencies, equivalent to that of the mutation rate.

  2. Neutral mutations usually remain within the gene pool as they have no impact on the organism.

  3. Beneficial mutations will spread through a population over generations through selection. If a mutation is beneficial and selected for by the environment an individual is in, it is considered the ultimate source of genetic variation in all populations.

New alleles enter a gene pool, changing the frequency of alleles at the time of mutation and after each new generation, and so therefore, mutation is a mechanism for evolution. Intraspecific variation (meaning within a species/population) can be quite small but are the foundation for evolutionary mechanisms. Evolution relies on genetic variation that is inheritable, meaning it can be passed to the next generation and provide an advantage in survival and reproduction in comparison to other organisms in the population.