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hereditary information, which is a major characteristic of sexual reproduction
and results in greater genetic diversity.
According to the widely accepted theory of evolution (for which Charles
Darwin laid the foundations in his 1859 topic “On the Origin of Species” [80],
and which was combined with the Mendelian knowledge of inheritance [218] in
the 1930s), life evolves by means of natural selection, mutations and genetic
drift [164]:
Natural selection is a natural process that results in the survival and
reproductive success of those individuals or groups that are best adjusted
to their environment (the often quoted “survival of the fittest”). This
process leads to the selection of genetic qualities that are best suited to
a particular environment.
Mutations are changes in the genome that occur spontaneously or due to
the influence of mutagens such as UV light or chemicals. They lead to
permanent loss ( deletion ), exchange ( substitution ) or addition ( insertion )
of bases in DNA sequences.
Genetic drift , in contrast to natural selection, refers to random changes
in the frequency of genes within populations. Over time, these changes
lead to the preservation or extinction of particular genes.
In short, evolution leaves its marks in the genomes, and can be tracked by
examination of molecular sequences.
3.1.1 Phylogenetic Trees
Phylogenetic trees areused to representrelationships betweenorganismsgraph-
ically [279, p. 267]. Similar to family trees that show the relationships between
Fig. 3.1 Universal phylogenetic tree of life (following [346])
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