BIOLOGICAL CLASSIFICATION ! ANNOTATE NCERT BOTANY

Organizing large amounts of information in a standardized way makes it easy to locate information and to communicate it to others. Scientists use an internationally accepted system for classifying and naming organisms. The system is based on the classification method introduced in 1758 by Carolus Linnaeus, a Swedish botanist regarded as the founder of modern taxonomy.



AdstockRFAdstockRF

The Linnaean system assigns each species a two-part scientific name composed of Greek or Latin words. The first part of the scientific name is the organism’s genus, a taxon that includes closely related species. Wolves, dogs, coyotes, and jackals are all members of the genus Canis. Conventionally, scientific names are always italicized or underlined, and the genus name is always capitalized.



Gary Kramer/USFWSGary Kramer/USFWS

The second part of the scientific name is called the species name, and it is particular to each species in the genus. The species name of the coyote is latrans; that of the gray wolf is lupus. The species name is always written in lowercase and italicized.

Together, the genus name and the species name comprise the scientific name of the species. Thus, the coyote’s scientific name is Canis latrans; the gray wolf’s name is Canis lupus. The two-part scientific name is sometimes called a binomial—from the Latin words bi-, meaning two, and nomen, meaning name.

Using scientific names helps scientists avoid the confusion that can arise when referring to an organism by its common, or everyday, name. For example, the name robin may refer to the European robin or to the American robin, or even to any of several other birds; however the robins’ scientific names—Erithacus rubecula and Turdus migratorius (European robin and American robin, respectively)—clearly identify the species being referenced. The scientific names show that the birds are distinct species and verify that they are not closely related, since each belongs to a different genus.

Levels of Classification

The classification system commonly used today is based on the Linnean system and has eight levels of taxa; from the most general to the most specific, these are domain, kingdom, phylum (plural, phyla), class, order, family, genus (plural, genera), and species. (For plants, the term division is generally used instead of phylum.) Each level is contained, or nested, within the level above it. For example, a genus contains one or more species; a family contains one or more genera; an order contains one or more families; and so on. The domain is the highest level of organization and is the largest group.

Following are overviews of each taxonomic level in modern biological classification. (For a detailed description of domains and kingdoms, see “Classification of Living Things” in the article living things.)