Classification:

Biological classification is a method by which biologists group and categorize species of organisms.

Aims of Classification:

Taxonomy:

The branch of biology that deals with classification are called taxonomy.

Systematic:

The branch which deals with classification and also traces the evolutionary history of organisms is known as systematics. The main aims of both these branches are:

1. To determine similarities and differences among organisms so that they can be studied easily.
2. To find the evolutionary relationships among organisms.

Principles of Classification/Basis of Classification:

1. Classification is based on the relationship amongst organisms and such a relationship is got through similarity in form or structure.
2. These similarities suggest that all organisms are related to one another at some point in their evolutionary histories. However, some organisms are more closely related than others. For example, sparrows are more closely related to pigeons than to insects. It means that the former two have common evolutionary histories.
3. Biologists have classified all the known organisms and subgroups based on similarities. These similarities are seen in structures, biochemistry, cytology, and genetics.
4. Modern genetics has provided another type of information to taxonomists. The genetic differences between two studied organisms can be determined and can be used for getting the idea about similarities and differences in their structures and functions.