Evolution
Part of the Biology series on
Evolution
Introduction
Mechanisms and processes
Adaptation
Genetic drift
Gene flow
Mutation
Natural selection
Speciation
Research and history
Evidence
Evolutionary history of life
History
Modern synthesis
Social effect
Theory and fact
Objections / Controversy
Evolutionary biology fields
Cladistics
Ecological genetics
Evolutionary development
Human evolution
Molecular evolution
Phylogenetics
Population genetics
Biology Portal ·
In biology, evolution is change in the genet-
ic material of a population of organisms from
one generation to the next. Though the
changes produced in any one generation are
small, differences accumulate with each gen-
eration and can, over time, cause substantial
changes in the organisms. This process can
culminate in the emergence of new spe-
cies.[1] Indeed, the similarities between or-
ganisms suggest that all known species are
descended from a common ancestor (or
ancestral gene pool) through this process of
gradual divergence.[2]
The basis of evolution is the genes that
are passed on from generation to generation;
these produce an organism’s inherited traits.
These traits vary within populations, with or-
ganisms showing heritable differences (vari-
ation) in their traits. Evolution itself is the
product of two opposing forces: processes
that constantly introduce variation, and pro-
cesses that make variants become more com-
mon or rare. New variation arises in two
main ways: either from mutations in genes,
or from the transfer of genes between popu-
lations and between species. In species that
reproduce sexually, new combinations of
genes are also produced by genetic recom-
bination, which
can
increase
variation
between organisms.
Two major mechanisms determine which
variants will become more common or rare in
a population. The first is natural selection, a
process that causes helpful traits (those that
increase the chance of survival and reproduc-
tion) to become more common in a popula-
tion and causes harmful traits to become
more rare. This