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Taxonomy (biology)

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Taxonomy is the scientific study of naming, defining, and classifying groups of biological organisms.

Linné-Systema Naturae 1735
Linné-Systema Naturae 1735

Scientists use this discipline to organize the vast variety of life based on shared characteristics. These organized groups are known as taxa, which is the singular form of the word taxonom. By grouping organisms into taxa, researchers can better understand the relationships between different living things. Taxonomy is a major component of a broader field called systematics. While the terms are sometimes used interchangeably, systematics often includes the study of evolutionary histories and environmental adaptations. Taxonomy focuses specifically on the description, identification, and naming of these biological groups.

The process of taxonomy follows a structured hierarchy of ranks. This hierarchy allows scientists to aggregate smaller groups into more inclusive, higher-level groups. The principal ranks used in modern biological classification are domain, kingdom, phylum, class, order, family, genus, and species.

Spindle diagram
Spindle diagram

For example, a species is a very specific group, but it belongs to a larger genus. That genus is part of a larger family, and so on, moving up through the ranks. This system creates a taxonomic hierarchy that maps out the connections between organisms. In botany, the term division is sometimes used instead of phylum to describe certain groups. This layered approach ensures that every organism has a specific place within the tree of life.

To decide how organisms should be grouped, scientists analyze various taxonomic characters. These characters provide the evidence used to infer the phylogeny, or evolutionary history, of different taxa.

Phylogenetics
Phylogenetics

Morphological characters are common, involving the study of external shapes, internal anatomy, or even embryology. Physiological characters examine metabolic factors or body secretions. Scientists also use molecular characters, which involve looking at DNA and RNA sequences or protein amino acid sequences. Even behavioral characters, such as courtship patterns, can serve as evidence. Ecological characters, including habitats and seasonal variations, also provide important data. By combining these different types of evidence, taxonomists can build a more accurate picture of biological relationships.

Taxonomy has a long history that stretches back to ancient civilizations. Early humans likely began naming organisms to distinguish between edible and poisonous plants. Egyptian wall paintings show medicinal plant illustrations, suggesting an early understanding of species. In ancient Greece, Aristotle classified organisms during his stay on the island of Lesbos. However, a truly scientific attempt to classify life did not occur until the 18th century. Early systems were often "artificial," meaning they used arbitrary criteria for grouping. For instance, Carl Linnaeus developed a sexual classification system for plants.

Linné-Systema Naturae 1735
Linné-Systema Naturae 1735

Linnaeus is now regarded as the founder of the current system of taxonomy.

The field has evolved through several distinct stages of scientific thought. Following the artificial systems, "natural systems" emerged in the late 18th and 19th centuries. Scientists like de Jussieu and de Candolle developed these systems by considering a more complete set of characteristics. These were pre-evolutionary in their thinking, focusing on observed patterns. The publication of Charles Darwin's "On the Origin of Species" in 1859 changed everything. This led to the rise of phyletic systems, which based classification on evolutionary relationships.

Cladogram vertebrata
Cladogram vertebrata

In the 1970s, cladistic methodology introduced classifications based on monophyly, or groups sharing a common ancestor.

Modern taxonomy is often divided into specific sub-disciplines like alpha and beta taxonomy. Alpha taxonomy is the practice of finding, describing, and naming taxa, particularly species. This term was discussed by William Bertram Turrill in the 1930s. He suggested that alpha taxonomy was the foundation for a much broader study. Beta taxonomy, a term used by Ernst Mayr in 1968, refers to the classification of ranks higher than the species level. This involves sorting species into groups of relatives and arranging them into a hierarchy. There is also microtaxonomy, which is the scientific work of defining species, and macrotaxonomy, which studies higher taxonomic ranks.

Taxonomic work can take the form of a monograph or a taxonomic revision. A revision is a new analysis of the variation patterns within a specific taxon. This analysis can use morphological, biochemical, or genetic data to find new insights. A monograph is a complete revision that covers a taxon comprehensively for the entire world. These revisions can lead to major changes, such as identifying new subtaxa or merging previous ones. This constant updating is necessary because new technology, like molecular genetics, provides more detailed data. As our tools improve, our understanding of the connections between all living things continues to grow.

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🖼️ Images & Media (6)
File:Huang-Quan-Xie-sheng-zhen-qin-tu.jpg
Huang-Quan-Xie-sheng-zhen-qin-tu.jpg
File:Linné-Systema Naturae 1735.jpg
Linné-Systema Naturae 1735.jpg
File:Spindle diagram.jpg
Spindle diagram.jpg
File:Cladogram vertebrata.jpg
Cladogram vertebrata.jpg
File:Nepenthes smilesii type specimen.jpg
Nepenthes smilesii type specimen.jpg
File:Phylogenetics.svg
Phylogenetics.svg
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