Science Contest Activity 2
Define any 4
In biology, a phylum is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division. The kingdom Animalia contains approximately 35 phyla; the kingdom Plantae contains 12 divisions. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta.
The composition of each class is determined by a taxonomist. Often there is no exact agreement, with different taxonomists taking different positions. There are no hard rules that a taxonomist needs to follow in describing a class, but for well-known animals there is likely to be consensus. For example, dogs are usually assigned to the phylum Chordata (animals with notochords); in the class Mammalia; in the order Carnivora.
Protozoa commonly range from 10 to 52 micrometers, but can grow as large as 1 mm, and are seen easily by microscope. The largest protozoa known are the deep-sea dwellingxenophyophores, which can grow up to 20 cm in diameter.
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organismscapable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are often used, such as similarity of DNA, morphology or ecological niche. Presence of specific locally adapted traits may further subdivide species into "infraspecific taxa" such as subspecies (and in botany other taxa are used, such as varieties, subvarieties, and formae).
Species that are believed to have the same ancestors are grouped together, and this group is called a genus. A species will be placed in only one genus (although taxonomic opinion might change). Similarity is best checked by the similarity of their DNA,[dubious ] but for practical reasons, other properties are used. All species are given a two-part name, a "binomial name". The first part of a binomial name is the generic name, the genus of the species. The second part is either called the specific name (a term used only in zoology) or the specific epithet (the term used in botany, which can also be used in zoology). For example, Boa constrictor is one of four species of the Boa genus. The first part of the name is capitalized, and the second part has a lower case. The binomial name is written in italics.
A usable definition of the word "species" and reliable methods of identifying particular species are essential for stating and testing biological theories and for measuring biodiversity, though other taxonomic levels such as families may be considered in broad-scale studies. Extinct species known only from fossils are generally difficult to assign precise taxonomic rankings, which is why higher taxonomic levels such as families are often used for fossil-based studies.
The total number of non-bacterial species in the world has been estimated at 8.7 million, with previous estimates ranging from two million to 100 million.
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