July 1, 2022

In taxonomy, the basic unit of biological classification is called species (from the Latin species). A species is a set of organisms or natural populations capable of interbreeding and producing fertile offspring, although —in principle— not with members of populations belonging to other species. In many cases, individuals that separate from the original population and isolate themselves from the rest can achieve sufficient differentiation to become a new species, therefore reproductive isolation from other populations is crucial. In short, a species is a reproductively homogeneous group of organisms, although very changeable over time and space. While in many cases this definition is adequate, it is often difficult to show whether two populations can interbreed and give fertile offspring (eg many organisms cannot be kept in the laboratory long enough). In addition to the fact that it is impossible to apply it to organisms that do not reproduce sexually (such as bacteria or extinct organisms known only from their fossils). At present, molecular techniques, such as those based on DNA similarity, are often applied. The common names of plants and animals sometimes correspond to their respective biological species (for example, "lion", "walrus" and "camphor tree"), but very often they do not: for example, the word duck refers to about twenty species of various genera, such as the domestic duck. For this reason, the binomial nomenclature is used for the denomination of species, through which each species is unequivocally defined with two words —for example, Homo sapiens, the human species—. In this nomenclature, the first term corresponds to the genus: the highest taxonomic rank in which species can be grouped.

Determination of limits

The determination of the limits of a species is purely subjective and, therefore, open to personal interpretation. Some common concepts are ancient, long before the scientific establishment of this taxonomic category. On the contrary, there are others with very vague limits, in which the systematicians are in complete disagreement. If the species were immutable, each one of them could be easily defined by saying that it is the set of individuals (that were, that are and that will be, if they do not become extinct) of qualitatively identical characteristics. An entity so determined is not really a species, but what is usually called a pure line or a clone. The delimitation of species directly affects important and current aspects such as Conservation Biology, or applied fields such as distribution modeling, from which very valuable information can be obtained. The number of species present in some territory is a way of estimating the richness, complexity and contribution to the natural heritage of its inhabitants.[1]

Ranking Levels

Subdividing, there are the following categories: Species (species) Subspecies (subspecies) Varietas (variety, race or ethnicity) Subvarietas (subvariety or subrace) Form subform

History of the species concept

The term species refers to three distinct but related concepts. The species rank, which is the most basic level of Linnaean taxonomy; species taxa, which are a group of organisms described and assigned to the species category, and biological species, which are entities capable of evolving. Regarding this, we must say that the idea of ​​evolution was already in classical antiquity. Anaximander claimed that the first creatures had emerged from the water to go on land; while Empedocles assured that they were separate parts that, at a given moment, came together, which reminds us of the theory of symbiogenesis