Need and importance of Biological classification keeping in view its historical background
There is a large collection of very dissimilar forms of organisms, found on Earth. Over 1.5 million types of animals and over 0.5 million types of plants are known to biologists and these are only a small percentage of the total types estimated to live on Earth. They range in complexity from small and simple bacteria to large and complex human beings. Some of them live in sea, some on land; some walk, others fly, and still others are stationary. Each has its own way of life i.e. getting food, avoiding unfavorable environmental conditions, finding a place to live, and reproducing its kind. When there are so many diverse kinds of organisms, it becomes difficult to learn about the characteristics of each.
To study such a large collection, biologists classify the organisms into groups and subgroups and for this task they require some system. Biological classification is a method by which biologists divide organisms into groups and subgroups.
Aims and Objectives: –
The aims and objectives of classification are as under: –
- i) Determine similarities and differences between organismsso that they can be studied easily.
- ii) Arrange organisms according to similarities and differences.
iii) Identify the organisms on the basis of structure and prominent features.
- iv) Finds out inter relationship of organisms.
- V) To find the evolutionary relationships among organisms.
Basis and Principles of Classification
The classification of organisms is based on such features or characters, which are similar in one kind of organisms and different in different kind of organisms. These characters may be about internal morphology, (anatomy), external morphology, physiology, cell structure, especially the number of chromosomes and chemical composition (especially of proteins) and embryology of the organisms. These characters help in study of intra specific (within the same species) and intra specific (between different) species differences. The presence of similar characters in different organisms indicates their common ancestry. This similarity because of common ancestral origin is called Homology e.g. arm of a monkey, flipper of a whale and wing of a bat show homology. They are dissimilar apparently but their internal structure (arrangement of bones and muscles) is same. These organs are called homologous organs. Due to this homology, we can, say that monkey, whale and bad had common ancestors and are placed in same large group “vertebrate”. This homology is proved to be very helpful in classification.