Systematics: It is the study of diversity of organisms and all their comparatives and evolutionary relationships.
Biological classification: It is the method of arranging organisms into categories that reflect their most significant features and relationships.
Identification: Identification is to determine the correct place of an organism in a previously established plan of classification.
Taxonomy: It is the study of principles and procedures of naming, identification and classification.
Biosystematics: The system of classification of organisms according to the history of evolution is called biosystematics.
Taxon: The term refers to the concrete biological objects included in a category.
Correlated characters: Those common features which are present among the species in a genus are called correlated characters.
Numerical Taxonomy/Phenetics: It is an approach to classification that employs numerical methods for evaluation of similarities and dissimilarities between the species.
Chemotaxonomy: A study of taxonomic relationship based on the distribution of certain characterstic chemical constituents is called chemotaxonomy.
Cytotaxonomy: It is a method of classification that uses cytological information of cells, chromosome number, their structure and behaviour during cell division.
Nomenclature: It refers to the assigning of correct names to organisms, based on the established rules and practices.
Bionomial Nomenclature: It is a system of giving scientific name to an organism, with two parts, the generic name, the specific name.
Trinomial Nomenclature: It is a system of giving scientific name to an organism, with three parts, the generic name, the specific name and sub-specific name.
Taxonomic Hierarchy: It is the arrangement of taxonomic groups in a definite order from higher to lower categories.
Key: A key is a scheme for identification of plants and animals, based on the contrasting characters.
Phylogeny: The evolutionary history of an organism/ a particular group of organisms is called phylogeny.
Bacteriophages: Those viruses which infect bacteria are called bacteriophages.
Photoautotrophs: Those organisms which make use of light energy for manufacturing their own food are called photoautotrophs.
Chemoautotrophs: These are the organisms which make use of the energy obtained by oxidising chemicals for manufacturing their food.