Evolution

In biology, evolution is the change in the heritable traits of a population over succeeding generations, as determined by shifts in the allele frequencies of genes. Through the course of time, this process results in the origin of new species from existing ones . All contemporary organisms are related to each other through regular descent, the products of cumulative evolutionary changes over billions of years. Evolution is the source of the huge diversity of extant and extinct life on Earth.

The basic mechanisms that produce evolutionary change are natural selection and genetic drift; these two mechanisms act on the genetic variation created by transformation, genetic recombination and gene flow. Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce. If those traits are heritable, they are passed to succeeding generations, with the result that beneficial heritable traits become more common in the next generation. Given enough time, this inactive process can result in varied adaptations to changing environmental conditions.