Chapter 2: Biological Classification
NCERT Biology | NEET-UG Preparation | Chapter Summary
Learning objective: Understand the development of biological classification, the five-kingdom system, the major characteristics of different kingdoms, and the differences between viruses, viroids, prions and lichens.
Need for Classification and Development of Classification Systems
The living world contains an enormous variety of organisms. Classification groups organisms according to their similarities and differences, making their study easier and more systematic.
Why is classification necessary?
- It helps organise the vast diversity of living organisms.
- It makes identification and scientific study easier.
- It helps understand relationships among organisms.
- It provides a systematic way to name and group organisms.
Development of classification
- Aristotle: Classified living organisms using simple observable characteristics. He grouped plants into categories such as herbs, shrubs and trees, and animals according to their habitats and other features.
- Two-kingdom classification: Organisms were divided into Plantae and Animalia. This system did not adequately distinguish prokaryotes from eukaryotes, unicellular from multicellular organisms, or fungi from plants.
- R. H. Whittaker (1969): Proposed the five-kingdom classification system.
Important: Modern classification considers features such as cell structure, body organisation, mode of nutrition, reproduction and evolutionary relationships.