Diversity in living organisms
On the planet Earth, there is a great diversity amongst living organisms. All the organisms vary in their external as well as internal structure, habit (eating, dwelling etc.), habitat (place of living), mode of nutrition (type of food they eat), and physiology. The Biodiversity of the earth is enormous. Currently Earth is believed to have over 40 million species of organisms, but only about 1.7 million have actually been described so far. All these living organisms share a great deal of diversity and also similarity, and we must classify them into groups in order to understand and study them systematically.
Taxonomy and systematics are the two main branches of biology which deal with classification.
- Taxonomy (In Greek, rendering of order) deals with identification, naming and classifying the living organisms. The term taxonomy was coined by Augustin Pyramus de Candolle.
- Systematics (In Greek, Put together) deals with systematic placing of organisms into groups or taxa on the basis of certain relationships between them. Carolus Linnaeus used this word for the first time in his book ‘Systema Naturae’.
Need for Classification
A grocery shop owner must take due care in arranging different items in different boxes or bags so that when a customer visits him he must be able to fulfill his need. If the items are not kept in a systematic way, it will be impossible for the shop owner to find the required item out of the loads and loads of items he has in his shop. In similar manner, in spite of great diversity among the animals of the animal kingdom is well arranged in a systematic way.
Classification makes the study of the biodiversity easier as the characters of a particular group or a family would apply to all the individuals of that group. Classification allows us to understand diversity better. For systematic study of animals different animals are arranged into minor and major groups on the basis of similarities and the differences in the characters.
History of Classification
- Aristotle and his student Theophrastus (370-282 BC) made the first attempt to classify organisms. They tried to classify the plants and animals on the basis of their body size form, habit and habitat.
- Aristotle who is known as the father of Zoology gave an account of classification of animals in his book Historia Animalium.
- Pliny (23-79 AD) introduced the first artificial system of classification in his book ‘Historia Naturalis’.
- John Ray, introduced the term species. He divided animals based on the presence and absence of blood. He also classified animals based on presence of gills, lungs, claws, teeth etc. He gave the definition for Species as ‘a reproducing unit’.
- Carolus Linnaeus, Father of Taxonomy developed the Binomial System of nomenclature which is the current scientific system of naming the species. He described about 5,900 species of plants in ‘Species Plantarum’ and 4200 species of animals in “Systema Naturae”.
Significance of classification
- Classification helps us gain the evolutionary knowledge. The sequence of evolution of animals can be studies well with the classification, like which animals have evolved first or when did the particular phylum evolve.
- Classification also makes way to understand the connecting links between the two groups of animals. Connecting links are the transitory stages between two groups of animals. With the help of classification definite position of connecting links can be made clear.
- Animals of one group are evolved from a common ancestor. This common ancestor can be traced out with the help of classification.
- With the help of classification, characters of animals with which they adapt to the given environment can be known.
- There are millions of organisms and it is difficult to study each of them. The study of selected animals of a particular group can give us an idea about the remaining animals of that group.
- The knowledge about relationships of different animals with other animal species comes from classification.
- Who is known as the father of Zoology? What is the book written by him?
- What is the need for classification?
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