Genetic variability occurs from
of chromosomes during
sexual and from DNA
mutationsin cellsand gametes.
Such variability individuals who
are carriers some new phenotypical
characteristics to their
ancestors.These individuals
submitted to environmental pressure
can bemore or less -succeeded
concerning survival or reproduction.
better succeeded transmit their
patrimony to a larger of
descendants increasing the of
their genes in population; those less
well-succeeded to transmit their
genes a small number of
decreasing the frequency of genes
in the population even becoming
extinct.This process called natural
selection (preservation organisms
that present more phenotypes
for the environmental they
face).