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Concept of Species

Species is the basic unit of classification. The term species was coined by John Ray, and in his book “Historia Generalis Plantarum” (3 volumes) in 1693 described species as a group of morphologically similar organisms arising from a common ancestor. Carolus Linnaeus in his book “Systema naturae” considered species as the basic unit of classification.

Species can be defined as a group of organisms that have similar morphology and physiology and can interbreed to produce fertile offsprings. In 1859 Charles Darwin in his book Origin of species explains the evolutionary connection of species by the process of natural selection.

The concept of species is an important but difficult one in biology, and is sometimes referred to the “species problem”. Some major species concepts are: Typological (or Essentialist, Morphological, Phenetic) species concept. Typology is based on morphology/phenotype.

Linnaeus (1707-1778), nearly 50 years later whose work was the most eminent and momentous in the taxonomy field, adopting a broader concept gave a new definition of species.

The biological species concept relies on behavioral data and emphasizes reproductive isolation between groups. The lineage species concept relies on genetic data and emphasizes distinct evolutionary trajectories between groups, which result in distinct lineages (branches on a phylogenetic tree).

Typological or Essentialist Species

Concept 2. Nominalistic Species
Concept 3. Biological Species
Concept 4. Evolutionary Species

Although the biological species concept has long been accepted by many evolutionary biologists (especially zoologists) as the best species concept, these kinds of problems have led to increasing attacks.

The natural world contains about 8.7 million species, according to a new estimate described by scientists as the most accurate ever. But the vast majority have not been identified – and cataloguing them all could take more than 1,000 years.

Organisms may appear to be alike and be different species. For example, Western meadowlarks (Sturnella neglecta) and Eastern meadowlarks (Sturnella magna) look almost identical to one another, yet do not interbreed with each other – thus, they are separate species according to this definition.