Biology Reference
In-Depth Information
Chapter 11
An Introduction to Phylogenetics
and Its Molecular Aspects
Gabriel Jîvasattha Bittar and Bernhard Pascal Sonderegger
1. Introduction
In general terms, phylogenetics is the study of the relationships between
evolving objects. The term derives from the Greek
phylon
(“race, tribe,
(old) family”) and
genos
(“birth, origin”),
gennêtikos
(“related to gener-
ation, to the genesis (of something)”).
Phylogenetics is part biology and part information science. It is a
discipline that helps to shed light on the ways in which biological objects
(organisms, genes) have appeared and evolved. Evolutionary science has
demonstrated that all living things have a common ancestry, but the root
of the tree of life on this planet lies nearly 4 billion years in the past. Since
then, evolution and phylogenesis have shaped a huge variety of biologi-
cal objects. On the whole, the tree of life is becoming more complex over
time. The process in which evolution tends to form more and more
diverse forms of life, in spite of (or maybe because of ) catastrophic
extinctions, is called cladogenesis (from the Greek
kladon
(“branch”)).
In addition to this process, the life forms themselves generally tend to
become more and more complex — a process called anagenesis (from the
Greek
ana
- (“up, to the top”)). Phylogenetics incorporates both clado-
genetics and anagenetics.
The essence of the cladogenetic part of phylogenetics can be illus-
trated by means of a simple graph. In Fig. 1, points C, D, and E — also
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