词条 | Systematics |
释义 |
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 (synonyms: cladograms, phylogenetic trees, phylogenies). Phylogenies have two components: branching order (showing group relationships) and branch length (showing amount of evolution). Phylogenetic trees of species and higher taxa are used to study the evolution of traits (e.g., anatomical or molecular characteristics) and the distribution of organisms (biogeography). Systematics, in other words, is used to understand the evolutionary history of life on Earth. Branches and applicationsIn 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, organelles, and cytoplasm. 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.[1] With the specific branches, researchers are able to determine the applications and uses for modern-day systematics. These applications include:
Definition and relation with taxonomyJohn Lindley provided an early definition of systematics in 1830, although he wrote of "systematic botany" rather than using the term "systematics".[2]In 1970 Michener et al. defined "systematic biology" and "taxonomy" (terms that are often confused and used interchangeably) in relationship to one another as follows:[3]
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{{who|date=July 2013}} claim systematics alone deals specifically with relationships through time, and that it can be synonymous with phylogenetics, broadly dealing with the inferred hierarchy{{citation needed|date=November 2014}} of organisms. This means it would be a subset of taxonomy as it is sometimes regarded, but the inverse is claimed by others.{{who|date=July 2013}} 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.[4] However, taxonomy, and in particular alpha taxonomy, is more specifically the identification, description, and naming (i.e. nomenclature) of organisms,[5] 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 and 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.{{citation needed|date=November 2014}} 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 (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 of Earth's various organisms through time. {{As of | 2014 | alt = Today's}} systematists generally make extensive use of molecular biology and of computer programs to study organisms. Taxonomic charactersTaxonomic characters are the taxonomic attributes that can be used to provide the evidence from which relationships (the phylogeny) between taxa are inferred.[6] Kinds of taxonomic characters include:[7] {{col-begin}}{{col-break}}
See also{{evolutionary biology}}
ReferencesNotes1. ^1 {{Cite news|url=http://www.biologydiscussion.com/animals-2/systematics-meaning-branches-and-its-application/32374|title=Systematics: Meaning, Branches and Its Application|date=2016-05-27|work=Biology Discussion|access-date=2017-04-12|language=en-US}} 2. ^Wilkins, J. S. What is systematics and what is taxonomy?. Available on http://evolvingthoughts.net 3. ^Michener, Charles D., John O. Corliss, Richard S. Cowan, Peter H. Raven, Curtis W. Sabrosky, Donald S. Squires, and G. W. Wharton (1970). Systematics In Support of Biological Research. Division of Biology and Agriculture, National Research Council. Washington, D.C. 25 pp. 4. ^Brusca, R. C., & Brusca, G. J. (2003). Invertebrates (2nd ed.). Sunderland, Mass. : Sinauer Associates, p. 27 5. ^{{Citation |last= Fortey |first= Richard |author-link= Richard Fortey |year=2008|title= Dry Store Room No. 1: The Secret Life of the Natural History Museum |publication-place= London |publisher= Harper Perennial |isbn= 978-0-00-720989-7 }} 6. ^Mayr, Ernst (1991). Principles of Systematic Zoology. New York: McGraw-Hill, p. 159. 7. ^Mayr, Ernst (1991), p. 162. Further reading
External links
2 : Evolutionary biology|Biological classification |
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