Polytypic Species are of three types:
Biotype: Members of same species inhabiting similar environment and having some genetic variations are known as biotypes. Variations found in these members are permanent. These members cannot interbreed among themselves.
Eg. Cauliflower, Cabbage, Knol-Khol are three biotypes of one species
Eeotypes: Members of same species inhabiting different environment and having some genetic variations are known as ecotypes. Variations are permanent. These members can interbreed among themselves but due to geographical barrier they can not interbreed.
Eg. Crow (Corvus splendense) found in different regions are ecotype of one species
Corvus splendense splendense - Indian crow
Corvus splendense insolence - Myanmar crow
Corvus splendense protegatus - Srilankan crow
Eeads or Ecophenes: Members of same species having some non genetic variations due to environment is called Ecads. These variations are temporary.
Eg. Every living being
This hypothesis is believed to be most acceptable.
Some definition related to species:
1. Linneon species: Those taxonomic species whose determination is based on morphology. They are called as linneon species. They are also called morpho-species or taxonomic species.
Eg. Most of species in taxonomy are linneon species
2. Microspecies or Joardan's species: Those species in which variations are very less are called Joardan's species. They reproduce asexually so they have very less variations.
3. Sibling species or Cryptic species: Members of species which are morphologically similar but reproductively isolated are known as Sibling species i.e. they cannot interbreed among themselves.
Sibling species is one taxonomic species (because these members have similar morphology) but they are different biological species. [Because they cannot interbreed]
Eg. Brassica oleracea
4. Allopatric species: Those species that are found in different geographical regions and have geographical barriess between them are known as allopatric species.
Geographical barriess are hills, oceans, himalyan mountains.
5. Sympatric species: The species found in similar geographical regions are sympatric species.
6. Allochronk species: The species found in different time periods. Eg. Man and Dinosaurs.
7. Synchronic species: Those species that are found in same era. Eg. Dinosaurs and Archaeopteryx.
8. Palaeo species: Those species that are extinct now and are found in the form of fossils. ego Dinosaurs
9. Neontological species: Those species which are living presently.
Biochemical resemblances are used in the identification of Moneran species.
* Genus comprises a group of related species which has more characters in common in comparison to species of other genera.
* Example: Potato, tomato and brinjal are three different species but all belong to the genus Solanum. Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) with several common features, are all species of the genus Panthera. This genus differs from another genus Felis which includes cats.
* Family, has a group of related genera with still less number of similarities as compared to genus and species.
* Families are characterised on the basis of both vegetative and reproductive features of plant species.
* Example: Three different genera Solanum, Petunia and Datura are placed in the family Solanaceae. Among animals for example, genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis (cats) in the family Felidae.
* Order being a higher category, is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family.
* Plant families like Convolvulaceae, Solanaceae 'are included in the order Polymoniales mainly based on the floral characters.
* The animal order, Carnivora, includes families like
Felidae and Cancidae.
* This category includes related orders.
* Example: Order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animals like tiger, cat and dog. Class Mammalia has other orders also.
* Classes comprising animals like fishes, amphibians, reptiles, birds along with mammals constitute the next higher category called Phylum. All these, based on the common features like presence of notochord and dorsal hollow neural system, are included in phylum Chordata. In case of plants, classes with a few similar characters are assigned to a higher category called Division.
* All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia in the classification system of animals. The Kingdom Plantae, on the other hand, is distinct, and comprises all plants from various divisions.