fundamental objective of a tree of life is to schematically represent
the relationships between different species, and groups of species.
Every species of organism, both extinct and extant, is derived through
evolution from the simplest organisms that first evolved hundreds
of millions of years ago. Therefore, it is theoretically possible
to discern how all species are related to eachother, from bacteria
to humans. In practise however, this rapidly becomes a complicated
and unrealistic goal.
the same way that a family tree provides an understanding into the
relationships between generations of a family, a phylogenetic tree
gives an idea of how organisms are related to one another, by reconstructing
evolutionary events. Although such data could be presented in a table,
they become far more readily accessible and far easier to understand
and interpret when converted into a pictorial format in which all
distances are summarised in a single-branching, tree-like diagram
(Majerus et al 1996).
are fundamentally two major processes used to translate the morphological
or molecular data obtained for species into phylogenetic trees. These
are phenetics and cladistics
(click for more information). Although both are very different, they
strive to achieve the same goal. There have been heated arguments over
the relative merits of phenetics and cladistics, with both approaches
contributing to the advancement of phylogenetics. One outcome of the
competitive use of both methods is that they have rescued comparative
morphology as a process of phylogenetics, from dormancy.