Species

Definition of species:

Talking about the definition of species, there is no one definite definition for species. It will differ depends on the scientists who used it and the place where we define it. Let we see the possible definitions for species.

• Species is considered as one of the taxonomic hierarchy and it is the lowest hierarchy of the taxonomy.
• Species is the group of organisms which are capable of interbreeding.
• Species is the group of organisms which shows high genetic similarity.
• Species is the population of organism which is localized in a particular area or habitat.

How to solve the issue of the definition of species?

As already mentioned above, there is no one definition for species, it will differ depends on the scientists and the place where we define it. To overcome this problem, biologists decide to have types of species depend on the definitions, because one particular definition will not suitable for all types of organisms.

For example: The definition "species is the group of organisms which are capable of interbreeding" is applicable only to sexually reproducing organisms but not to asexually reproducing organisms.

There are list of species based on the definitions -

• Morphological species: Organisms shows close resemblance in their morphology is considered as morphological species. But this idea was highly criticized because organisms from two different species (with high genetic variation) show morphological similarity. Example: snakes and worms.
• Biological / isolation species: Population which are capable of interbreeding. This idea was not applicable to asexual reproducing populations.
• Biological / reproductive species: Population which are able to reproduce naturally fertile offspring of both the genders. But, when infertile offspring are produced, it is not included in the same species. Example: Infertile mule born for horse and donkey.
• Evolutionary / Darwinian species: Population shares the ancestral lineage is considered as evolutionary species. When the population shows different characters, it leads to the formation of sub-species or new species. This is the mechanism of evolution.
• Ecological species: When population of organisms localized in a particular area or niche in the environment, then it is called ecological species.
• Genetic species: Species based on the similarity of DNA.