Concept of Species

“Species are often defined as a group of individuals with similar characteristics, where they can interbreed to produce fertile offsprings.“

To differentiate between different types of living organisms, species is used as the principal natural unit in biology.

Important Concept Of Species

Four most important concepts of species are:

Typological Species Concept

In this concept, there is a finite number of varieties of living organisms that exist on earth. These types do not exhibit any relationship with each other. Such varieties are termed as species. This inequality is regarded as an unimportant and irrelevant phenomenon.

Aristotle and Plato stated this concept in their philosophies. In the year of 1954 and 1956, Cain regarded the Typological species concept as the morphospecies concept. As the members of the species or a taxon can be identified by their essential characteristics, a group of scientists refer to this as essentialist species concept.

Morphospecies concept states that the species can be differentiated from other species by their physical features and can be identified by their morphological attributes. This is called the morphological species concept.

Also Read: Speciation and Evolution

Nominalistic Species Concept

The nominalistic species concept is the concept of Occam and his followers, of the belief that nature only produces individuals. Species are the creation of man. In nature, they lack definite exis­tence. These concepts do not have any scientific basis.

It believes that the species have been inven­ted to be referred to big numbers of individuals jointly. During the 18th century in France, this concept was in demand and even now is used by some botanists.

Also Read: Endemic Species

Biological Species Concept

In the middle of the 18th century, a fresh concept called the biological species concept appeared. This concept was acknowledged in the later half of the nineteenth-century once Darwin’s “Origin of Species” was published (in 1859). This is also known as Newer Species concept.

K. Jordan was the first to formulate this concept in 1905. Later in 1940, Mayr supported this concept. As per this concept, “a species is a group of interbreeding natu­ral population that is reproductively iso­lated from other such groups”. Mayr described that the members of a species exhibit these attributes:

1. Reproductive community: For the purpose of reproduction the individuals of a species recognize one another as potential mates.
2. Ecological Unit: The species’ mem­bers differ from each other due to many attributes, but all the members cooperatively form a unit. They interact with other species as a unit in any environment.
3. Genetical unit: Species comprises a large, inter-communicating gene pool, although the individual is simply a non-permanent vessel comprising a small part of the contents of the gene pool for a shorter duration.

Evolutionary Species Concept

The flaws of the biological species concept had led the palaeontologists to formulate the evolutionary species concept.

1. Simpson (in 1961) had defined it as “an evolu­tionary species is a lineage (an ancestral- descendant sequence of populations) evol­ving separately from others and with its own unitary evolutionary role and tendencies”.
2. Wiley (in 1978) had provided a revised definition of the evolutionary species concept. He stated that “an evolutionary species are a single lineage of ancestral-descendant popu­lation which draws its identity from other such lineages and has its own evolutionary tendencies and historical fate”.

Also Read: Anagenesis

Types of Species

Following are the different types of species:

Taxonomic Species

It includes a group of morphologically similar organisms.

Microspecies

The population is obtained from a single parent.

Biological Species

It includes the population that involves sexually reproducing individuals.

Evolutionary Species

It is a combination of sexually reproducing organisms, phyletic lineages and uniparental organisms.

Successional Species

It includes phyletic lineages.

Further Reading: Flagship Species

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