Evolution is one of the major unifying concepts of modern biology. Entailed with the concept of evolution, are the mechanisms that are involved with evolutionary change. There are many mechanisms that lead to evolutionary change. Random changes in the genetic composition of a population are called genetic drift.

The mechanisms that cause random change include mutation, founder effects, and genetic bottlenecks. All genetic variation originates from mutation. A mutation is a hereditary change in the DNA sequence or in chromosome number, form, or structure. Mutations can be point mutations, deletions and insertions, or changes in the total amount of DNA and number of genes. Mutations are not random, in the sense that they occur more frequently in some locations, and under some circumstances, than others. However, mutations are random in the sense that there is no systematic relationship between their phenotypic effect and the needs of the organism in which they occur.

New populations are sometimes founded by a small group of individuals where gene frequencies are very different from the frequencies in the parent population, only by chance. This is known as the founder effect. Along the same lines, if because of some catastrophe only a few individuals survive to breed, the genetic composition of the population changes dramatically as it passes through a genetic bottleneck. When a population passes through a bottleneck, many alleles are lost and others rise to higher frequency. Evolution is one of the major unifying concepts of modern biology. Entailed with the concept of evolution, are the mechanisms that are involved with evolutionary change.

There are many mechanisms that lead to evolutionary change. Random changes in the genetic composition of a population are called genetic drift. The mechanisms that cause random change include mutation, founder effects, and genetic bottlenecks. All genetic variation originates from mutation. A mutation is a hereditary change in the DNA sequence or in chromosome number, form, or structure. Mutations can be point mutations, deletions and insertions, or changes in the total amount of DNA and number of genes.

Mutations are not random, in the sense that they occur more frequently in some locations, and under some circumstances, than others. However, mutations are random in the sense that there is no systematic relationship between their phenotypic effect and the needs of the organism in which they occur. New populations are sometimes founded by a small group of individuals where gene frequencies are very different from the frequencies in the parent population, only by chance. This is known as the founder effect. Along the same lines, if because of some catastrophe only a few individuals survive to breed, the genetic composition of the population changes dramatically as it passes through a genetic bottleneck. When a population passes through a bottleneck, many alleles are lost and others rise to higher frequency..