The aim of phylogenetics is to reconstruct family trees and base
classifications on them.
Phylogeny: A family tree of species.
Phylogenetics: The study of family trees.
- Phylogenetic methods use both the fossil record and resemblances among
living species as evidence to reconstruct phylogenies. Species sharing
many similarities are considered to be descendents of a common ancestor
that also shared these similarities. When conflicting evidence arises
from different characters, further study is undertaken to see whether
some of the similarities could have evolved by convergence.
- An important task in phylogenetics is therefore recognizing
homology (resemblance due to common ancestry) and distinguishing
it from analogy or convergence.
- The aim of classification based on phylogenetics is to group together
those species that derive their similarities from a common ancestor.
That means that, insofar as possible, each taxon should be made
monophyletic by including the common ancestor within the taxon.
Taxonomy is the theory behing the making of classifications.
- Phenetic taxonomy: Classifications based on resemblance alone
have long been in disfavor because they do not distinguish convergence
from other causes of resemblance.
- Phylogenetic taxonomy: Modern classifications are based on
phylogenetics, meaning that species that share a common ancestry are
grouped together as much as possible. Strict adherence to this principle
is the basis of cladistics. Cladistic taxonomists construct family
trees first, then base their classifications strictly on the geometry of
branching, ignoring such matters as the diversity or degree of change within
each branch.
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