Biological systematics is the study of the diversification of living forms,
both past and present, and the relationships among living things
through time. Relationships are visualized as evolutionary trees.
Phylogenies have two components, branching order and branch length.
Phylogenetic trees of species and higher taxa are used to study the evolution of
traits and the distribution of organisms. Systematics, in other words,
is used to understand the evolutionary history of life on Earth.
Definition and relation with taxonomy John Lindley provided an early
definition of systematics in 1830, although he wrote of "systematic botany"
rather than using the term "systematics".
In 1970 Michener et al. defined "systematic biology" and "taxonomy" in
relationship to one another as follows: Systematic biology is the field that
provides scientific names for organisms, describes them, preserves collections of
them, provides classifications for the organisms, keys for their
identification, and data on their distributions, investigates their
evolutionary histories, and considers their environmental adaptations. This is
a field with a long history that in recent years has experienced a notable
renaissance, principally with respect to theoretical content. Part of the
theoretical material has to do with evolutionary areas, the rest relates
especially to the problem of classification. Taxonomy is that part of
Systematics concerned with topics to above.
The term "systematics" is sometimes used synonymously with "taxonomy", and may be
confused with "scientific classification". Webster's 9th New
Collegiate Dictionary of 1987 treats "classification", "taxonomy", and
"systematics" as synonymous. According to this work the terms originated in
1790, c. 1828, and in 1888 respectively. Some claim systematics alone deals
specifically with relationships through time, and that it can be synonymous with
phylogenetics, broadly dealing with the inferred hierarchy of organisms, which
means it would be as subset of taxonomy as it is sometimes regarded, but the
inverse is claimed by others. Europeans tend to use the terms
"systematics" and "biosystematics" for the field of the study of biodiversity
as a whole, whereas North Americans tend to use "taxonomy" more frequently.
However, taxonomy, and in particular alpha taxonomy, is more specifically the
identification, description, and naming of organisms, while "classification"
focuses on placing organisms within hierarchical groups that show their
relationships to other organisms. All of these biological disciplines can deal
both with extinct and with extant organisms.
Systematics uses taxonomy as a primary tool in understanding, as nothing about
an organism's relationships with other living things can be understood without
it first being properly studied and described in sufficient detail to
identify and classify it correctly. Scientific classifications are aids in
recording and reporting information to other scientists and to laymen. The
systematist, a scientist who specializes in systematics, must, therefore, be able
to use existing classification systems, or at least know them well enough to
skilfully justify not using them. Phenetics was an attempt to determine
the relationships of organisms through a measure of overall similarity, making no
distinction between plesiomorphies and apomorphies. From the late-20th century
onwards, it was superseded by cladistics, which rejects plesiomorphies
in attempting to resolve the phylogeny of Earth's various organisms through
time. Today's systematists generally make extensive use of molecular biology
and of computer programs to study organisms.
Taxonomic characters Taxonomic characters provide the
evidence from which relationship between taxa is inferred. Kinds of taxonomic
characters: See also
Biological classification Cladistics - a methodology in
systematics Evolutionary systematics - a school of
systematics Global biodiversity
Phenetics - a methodology in systematics that does not infer phylogeny
Phylogeny - the historical relationships between lineages of organism
16S ribosomal RNA - an intensively studied nucleic acid that has been
useful in phylogenetics Phylogenetic comparative methods - use
of evolutionary trees in other studies, such as biodiversity, comparative
biology. adaptation, or evolutionary mechanisms
Scientific classification and Taxonomy - the result of research in systematics
References = Notes =
= Further Reading = Schuh, Randall T. and Andrew V. Z.
Brower. 2009. Biological Systematics: Principles and Applications, 2nd edn.
ISBN 978-0-8014-4799-0 Simpson, Michael G. 2005. Plant
Systematics. ISBN 978-0-12-644460-5 External links
Society of Australian Systematic Biologists
Society of Systematic Biologists Willi Hennig Society