Why are the classification systems changing every now and then?

(i) Biology is a natural science concerned with the study of all living organisms.

(ii) The term 'Biology' was used for the first time as a scientific term by the German physiologist Gottfried.

(iii) Three major branches of biology are: Zoology, Botany and Microbiology.

2. Diversity in the Living World:

(i) Our planet is so rich with life that scientists do not even know exactly how many species may exist.

(ii) So far, we have identified and scientifically named about $1.7-1.8$ million species, but a large number still remains unknown.

(iii) Living organisms vary in terms of size, colour, habitat, physiological and morphological features.

3. Taxonomic Categories:

(i) To facilitate the study of kinds and diversity of organisms, biologists have evolved certain rules and principles for identification, nomenclature and classification of organisms.

(ii) Taxonomy is the science of naming and classifying organisms.

(iii) Carolus Linnaeus is known as the father of taxonomy.

(iv) Taxonomy is useful in agriculture, forestry, industry and in general for knowing our bio-resources and their diversity.

(v) The basics of taxonomy like identification, naming and classification of organisms are universally evolved under international codes.

(vi) Systematics is the study of biological diversity and its origins.

(vii) The term systematics was originally coined by Swedish botanist Carolus Linnaeus.

(viii) Based on the resemblances and distinct differences, each organism is identified and assigned a correct scientific/biological name comprising two words as per the binomial system of nomenclature.

(ix) An organism represents/occupies a place or position in the system of classification.

(x) There are many categories/ranks and are generally referred to as taxonomic categories or taxa.

(xi) All the categories constitute a taxonomic hierarchy.

4. Taxonomical Aids:

(i) Taxonomists have developed a variety of taxonomic aids to facilitate identification, naming and classification of organisms.

(ii) These studies are carried out from the actual specimens which are collected from the field and preserved.

(iii) It requires special techniques for collection and preservation of specimens in herbaria and museums.

(iv) Live specimens, on the other hand, of plants and animals, are found in botanical gardens or in zoological parks.

(v) Taxonomists also prepare and disseminate information through manuals and monographs for further taxonomic studies.

(vi) Taxonomic keys are tools that help in identification based on characteristics.