Biosystematics: Steps and Categories

The steps in biosystematic investigation are as follows

  • Sampling of taxon and its population and cytological study of the chromosome of many population within geographical races, species and genera; differences in chromosome number, their morphology, behavior of meiosis indicated genetic differences.
  • Determination of ability of the different population to hybridize and study of vigour and fertility of the hybrids.
  • Study of homologies of the chromosomes is the hybrids at meiosis. This indicates degree of genetic relationship.
  • Synthesis of the data in the previous 3, along with that of compartative morphology and geographical distributions.

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Biosystematics refers to the isolation and indication of a plant population into living biotic units and classify them upto a specific level for specific purposes.

Biosystematic Categories

Biosystematic categories are different from the normal taxonomic categories. The biosystematic categories are described below


Ecotype is the basic unit of biosystemátics. Ecotype is a population that is different from other population by morphological and physiological characters. An ecotype is capable of forming fully fertile hybrid by sexual reproduction with another ecotype of the same ecospecies but due to environmental barriers (eg. hills, oceans), genes may not exchange normally.

Different ecotypes of the same ecospecies are differentiated by each other by several genes but they are not differentiated by genetic barriers. They are differentiated only by ecological barriers.

The world biotype is used by in the description of biosystemátics. A biotype is formed by the plants having same genotype.


Ecospecies is a group of plants formed by one or more ecotype and they are capable of exchanging gene with other ecospecies of the same cenospecies. Cross between two ecospecies of the same cenospecies form incompletely sterile progeny but if they are fertile then F2 generation expresses weak characters like less growth, susceptible to diseases etc.

Some taxonomists consider ecospecies as the sub-species or species of classical taxonomy.


Cenospecies is a group of plants formed by one or more ecospecies and considering their cellular, morphological and experimental information, they are thought to have originated from same evolutionary line. Cross between two cenospecies of same comparium results in the complete sterile progeny.

Some taxonomists consider conospecies as the section on subsection of the genus of classical taxonomy.


A comparium is composed of one one more cenospecies. Intercross between two comparium is not possible.

Some taxonomists consider comparium as the genus of Classical taxonomy


Revised by

  1. Md. Siddiq Hasan on August 12, 2020
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About Abulais Shomrat

Currently in 4th year (Hons) in the Department of Botany, University of Dhaka. Planned to have multiple careers one by one but promised to be with 'Plantlet' as long as it's primary stage remains unfinished. Email: abulaisshomrat@gmail.com. Minimum monthly resolution - Publish (1), Revise (3), Share (5)

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