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Biological Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution.Based on definition from: Despite the c ...
systematics is the study of the diversification of living forms, both past and present, and the
relationships Relationship most often refers to: * Interpersonal relationship, a strong, deep, or close association or acquaintance between two or more people * Correlation and dependence, relationships in mathematics and statistics between two variables or se ...
among living things through time. Relationships are visualized as evolutionary trees (synonyms:
cladograms A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to de ...
,
phylogenetic tree , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary rela ...

phylogenetic tree
s, phylogenies). Phylogenies have two components: branching order (showing group relationships) and branch length (showing amount of evolution). Phylogenetic trees of species and higher
taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name ...
are used to study the evolution of traits (e.g., anatomical or molecular characteristics) and the distribution of organisms (
biogeography Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isol ...
). Systematics, in other words, is used to understand the evolutionary history of life on Earth. The word systematics is derived from Latin word `systema', which means systematic arrangement of organisms.
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement as Carl von LinnéBlunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the modern sys ...
used '
Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomencl ...
' as the title of his book.


Branches and applications

In the study of biological systematics, researchers use the different branches to further understand the relationships between differing organisms. These branches are used to determine the applications and uses for modern day systematics. Biological systematics classifies species by using three specific branches. ''Numerical systematics'', or ''biometry'', uses biological statistics to identify and classify animals. ''Biochemical systematics'' classifies and identifies animals based on the analysis of the material that makes up the living part of a cell—such as the
nucleus ''Nucleus'' (plural nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA ...

nucleus
,
organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the su ...
s, and
cytoplasm In cell biology, the cytoplasm is all of the material within a cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The main compone ...
. ''Experimental systematics'' identifies and classifies animals based on the evolutionary units that comprise a species, as well as their importance in evolution itself. Factors such as mutations, genetic divergence, and hybridization all are considered evolutionary units. With the specific branches, researchers are able to determine the applications and uses for modern-day systematics. These applications include: * Studying the diversity of organisms and the differentiation between extinct and living creatures. Biologists study the well-understood relationships by making many different diagrams and "trees" (cladograms, phylogenetic trees, phylogenies, etc.). * Including the scientific names of organisms, species descriptions and overviews, taxonomic orders, and classifications of evolutionary and organism histories. * Explaining the biodiversity of the planet and its organisms. The systematic study is that of conservation. * Manipulating and controlling the natural world. This includes the practice of 'biological control', the intentional introduction of natural predators and disease.


Definition and relation with taxonomy

John Lindley John Lindley FRS (5 February 1799 – 1 November 1865) was an English botanist, gardener and orchidologist. Early years Born in Catton, near Norwich, England, John Lindley was one of four children of George and Mary Lindley. George Lindley was a ...
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 Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
" (terms that are often confused and used interchangeably) in relationship to one another as follows:
Systematic biology (hereafter called simply systematics) is the field that (a) provides scientific names for organisms, (b) describes them, (c) preserves collections of them, (d) provides classifications for the organisms, keys for their identification, and data on their distributions, (e) investigates their evolutionary histories, and (f) 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 (topics e and f above), the rest relates especially to the problem of classification. Taxonomy is that part of Systematics concerned with topics (a) to (d) above.
The term "taxonomy" was coined by
Augustin Pyramus de Candolle Augustin Pyramus (or Pyrame) de Candolle (, , ; 4 February 17789 September 1841) was a Swiss botanist. René Louiche Desfontaines launched de Candolle's botanical career by recommending him at an herbarium. Within a couple of years de Candolle ...
while the term "systematic" was coined by
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement as Carl von LinnéBlunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the modern sys ...
the father of taxonomy. Taxonomy, systematic biology, systematics, biosystematics, scientific classification, biological classification, phylogenetics: At various times in history, all these words have had overlapping, related meanings. However, in modern usage, they can all be considered synonyms of each other. For example, Webster's 9th New Collegiate Dictionary of 1987 treats "classification", "taxonomy", and "systematics" as synonyms. 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 In biology, phylogenetics (from Greek φυλή/φῦλον () "tribe, clan, race", and γενετικός () "origin, source, birth") is a part of systematics that addresses the inference of the evolutionary history and relationships among or wit ...

phylogenetics
, broadly dealing with the inferred hierarchy of organisms. This means it would be a 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 study of biodiversity as a whole, whereas North Americans tend to use "taxonomy" more frequently. However, taxonomy, and in particular
alpha taxonomy In biology, taxonomy () is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
, is more specifically the identification, description, and naming (i.e. nomenclature) 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 with both
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and rec ...
and
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, s ...
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 In biology, phenetics ( el|phainein - to appear) , also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually in morphology or other observable traits, regardless of their phylogeny or evolutionary relati ...
was an attempt to determine the relationships of organisms through a measure of overall similarity, making no distinction between
plesiomorph [[File:Cladogram imaginary birds.jpg|Imaginary cladogram. The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorp ...
ies (shared ancestral traits) and [[apomorphies (derived traits). From the late-20th century onwards, it was superseded by [[cladistics, which rejects plesiomorphies in attempting to resolve the
phylogeny , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary rela ...

phylogeny
of Earth's various organisms through time. systematists generally make extensive use of
molecular biology#REDIRECT Molecular biology#REDIRECT Molecular biology {{Redirect category shell|1= {{R from other capitalisation ...
{{Redirect category shell|1= {{R from other capitalisation ...
and of
computer programs A computer program is a collection of instructions that can be executed by a computer to perform a specific task. A computer program is usually written by a computer programmer in a programming language. From the program in its human-readable f ...
to study organisms.


Taxonomic characters

Taxonomic characters are the taxonomic attributes that can be used to provide the evidence from which relationships (the
phylogeny , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary rela ...

phylogeny
) between taxa are inferred. Kinds of taxonomic characters include:Mayr, Ernst (1991), p. 162. * Morphological characters ** General external morphology ** Special structures (e.g. genitalia) ** Internal morphology (anatomy) ** Embryology ** Karyology and other cytological factors * Physiological characters ** Metabolic factors ** Body secretions ** Genic sterility factors * Molecular characters ** Immunological distance ** Electrophoretic differences ** Amino acid sequences of proteins ** DNA hybridization ** DNA and RNA sequences ** Restriction endonuclease analyses ** Other molecular differences * Behavioral characters ** Courtship and other ethological isolating mechanisms ** Other behavior patterns * Ecological characters ** Habit and habitats ** Food ** Seasonal variations ** Parasites and hosts * Geographic characters ** General biogeographic distribution patterns ** Sympatric-allopatric relationship of populations


See also

*
Biological classification In biology, taxonomy () is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
*
Cladistics Cladistics (, from Greek , ''kládos'', "branch") is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships ...
- a
methodology Methodology is "'a contextual framework' for research, a coherent and logical scheme based on views, beliefs, and values, that guides the choices researchers r other usersmake". It comprises the theoretical analysis of the body of methods and ...
in systematics *
Evolutionary systematics Evolutionary taxonomy, evolutionary systematics or Darwinian classification is a branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship (shared descent), progenitor-descendant relatio ...
- a school of systematics *
Global biodiversity Global biodiversity is the measure of biodiversity on planet Earth and is defined as the total variability of life forms. More than 99 percent of all species that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's cu ...
*
Phenetics In biology, phenetics ( el|phainein - to appear) , also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually in morphology or other observable traits, regardless of their phylogeny or evolutionary relati ...
- a methodology in systematics that does not infer phylogeny *
Phylogeny , based on completely sequenced genomes. A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary rela ...

Phylogeny
- the historical relationships between lineages of organism *
16S ribosomal RNA 16S ribosomal RNA (or 16S rRNA) is the RNA component of the 30S small subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRN ...
- an intensively studied nucleic acid that has been useful in phylogenetics *
Phylogenetic comparative methods Phylogenetic comparative methods (PCMs) use information on the historical relationships of lineages (phylogenies) to test evolutionary hypotheses. The comparative method has a long history in evolutionary biology; indeed, Charles Darwin used differ ...
- use of evolutionary trees in other studies, such as
biodiversity Biodiversity is the biological variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic, species, and ecosystem level. Terrestrial biodiversity is usually greater near the equator, which is the result of th ...
, comparative biology. adaptation, or evolutionary mechanisms *
Scientific classification In biology, taxonomy () is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
and
Taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
- 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.'' * Simpson, Michael G. 2005. ''Plant Systematics''. * Wiley, Edward O. and Bruce S. Lieberman. 2011. "Phylogenetics: Theory and Practice of Phylogenetic Systematics, 2nd edn."


External links


Society of Australian Systematic Biologists

Society of Systematic Biologists

The Willi Hennig Society
{{Authority control Category:Evolutionary biology
Category:Biological classification {{Cat main|Taxonomy (biology) Category:Biology Category:Scientific classification ...