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Species

Species is a definitional unit used by biologists and other life scientists to systematically classify the enormous numbers of life forms on the earth. The basic unit of classification is species, followed by larger groupings of related plants or animals. The term species was first used by the ancient Greeks. Taken from the Greek, the word ideos meant the shape or visible form of something—its form made it rationally comprehensible. Logically specifying the form of something as a specie of some species answered the question, “What is it?”

Millions of species have been identified and many more are discovered virtually every day. In general, a species includes all of the individual members of its natural population that are descended from common ancestors and that can breed indefinitely with each other. The interbreeding population share similar characteristics including appearance, genetics, and relatively recent ancestors. The factor of interbreeding is a very important defining characteristic. The interbreeding members of a species exchange hereditary material or genes with each other to produce offspring after their own kind, and a common gene pool is established within the species. Generally, differences between species prevent interbreeding through reproductive isolating mechanisms.

There are many species that are closely related to other similar species that do not normally interbreed. For example, wolves and dogs are closely related but do not normally interbreed, although in this particular case, they are capable of interbreeding. In some species, interbreeding produces hybrids, most of which are sterile and cannot breed. For example, horses and donkeys can and do interbreed, but the offspring are usually sterile mules produced by a male donkey and a female horse.

Classification

The term species is used in the scientific classification of plants and animals in order to provide a taxonomic system for organizing all plants and animals. The current system groups all individual plants and animals into a basic group called a “species.” The individuals in a species are assigned two names in Latin, which are often derived from Greek or Latin words.

The Latin naming system is called a binomial system because it uses two names as identifiers assigned to a new species. The first name is the genus name of the species and the second name is the special identifying name of the species. The binominal system of nomenclature enables scientists to name the plants and animals in exactly the same standard way regardless of individual variations. The binomial nomenclature enables individuals to be grouped into a useful category everywhere around the world. For example, dogs, found everywhere, are classified as the species Canis domesticus. The domesticus refers to its ancient taming by humans and close association with human domiciles. The naming of species is done by scientific bodies. They may use a name that is descriptive of a characteristic of the species or that recognizes the discoverer of a newly identified species. To aid in the work there are now international codes of ontological and botanical nomenclature.

However, many biologists and other life scientists who regularly engage in taxonomic work doubt whether one single scheme of classification will fit all life forms. Among biologists and other life scientists the so-called “species problem” is a controversial subject. There is considerable disagreement about how best to identify species, what constitutes a useful name, what is a genuine species, and how it is to be distinguished from similar but apparently different species that are not really different species but just differences in individuals. For example, black- and blonde-colored cocker spaniels are not different species, but rather individuals with different characteristics. Such obvious differences are not always apparent among some of the more obscure forms of life.

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