Subspecies, Varieties and Rances.

  Principles for Delimiting a Species. The different members of a species whether morphologically similar or dissimilar are able to  interbreed freely and produce fertile offspring. All the members whether present in one population or different populations found in remote areas of the globe are derived from a common ancestor. The members resemble one another more than they resemble individuals of any other species. There is a complete anatomical similarity. All the members of a species have similar karyotype  there is similarity in the number, size, shape and behaviour of meiotic chromosomes. All the individuals of a species contain similar genetic material. There is a broad similarity in morphological characters. At the molecular level there is similarity in the types of proteins, enzymes, hormones and other biochemical’s.

                                           

Subspecies, Varieties and Rances.

They are categories inferior in rank to species. Categories area raised depending upon the degree of resemblances and differences. The term subspecies is used more commonly by zoologists, while variety is  used more commonly by botanists. Populations distinguishing characteristics that separate its members from other members of the species.

Race is a groups of individuals within a species forming a nearly permanent breed. Some authors use the term as synonym with subspecies. Others consider race to be subordinate to sub species. For example, human beings belong  belong to subspecies Homo sapiens. There are seven main human races. All of which differ in pigmentation of skin, hair, size and shape of nose, proportion of the body, etc. However, except for  geographical or spatial barriers, members of different races, varieties and subspecies freely interbreed.

1.       Genus. It is a group or assemblage of related species which resemble one another in certain correlated characters. Correlated characters are those similar or common features which are used in delimination of a taxon above the rank of species. All the species of genus are presumed to have evolved from a common ancestor.

It is not essential for a genus to have several species. There are geners  which have only one species. They are called monotypic. Others are known as those as polytypic. Thus the genus solanum has a large  number of closely related species, e.g., S. tuberosum , s. melongena , S.nigrum, S. surratense.

Similarly Lion, Tiger, Leopard, Jaguar are closely related species which have been placed in the genus panthers. The animals are respectively named as panther leo, P. tigris, P. Pardus and P. once. These ferocious animals are relaed with some differences to cats included in the genus Felis, E.g., F. domestica, F. Bengolensis, F. mormorata, F. chaus, F. viverrina and F. temminki.

Family. It is taxonomic category which contains one or more related. All the genera of family have some common features or correlated characters. They are separable from genera of a related family by important and characteristic differences in both vegetative and reproductive features. Thus the genera of cats and leopard are of family canidae. Similarly, the family Solanaceae   contains a number of genera like Solanum, Withania, Datura, Petunia and NIcotiana. They are distinguishable from the genera of the related family convolvulacea