Basis of Classification — Class 7 Science (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 7 Science, Term 2 — Chapter 5. Sorting the living world.
1. About this chapter
This chapter covers the need for classification, the taxonomic hierarchy, the five-kingdom classification, and binomial nomenclature.
2. Classification and its hierarchy
- Classification groups living things by their similarities and differences (both are needed). There are about 8.7 million species of living organisms on Earth.
- Living things are arranged in a hierarchy: Kingdom → Phylum → Class → Order → Family → Genus → Species. The largest division is the Kingdom, and the basic unit is the species.
3. The five-kingdom classification
- R. H. Whittaker proposed the five-kingdom classification: Monera, Protista, Fungi, Plantae and Animalia.
| Kingdom | Features / examples |
|---|---|
| Monera | unicellular, no true nucleus — bacteria, blue-green algae |
| Protista | mostly unicellular eukaryotes (and a few simple multicellular ones) |
| Fungi | non-green and non-photosynthetic (mushrooms, yeast, moulds) |
| Plantae | green, photosynthetic plants |
| Animalia | multicellular animals |
4. Binomial nomenclature
- Binomial nomenclature is a universal two-name system for naming organisms, introduced by Gaspard Bauhin (1623).
- Each organism has two names — the genus name (first) and the species name (second). For example, the pigeon is Columba livia.
5. Worked examples
Example 1. Who proposed the five-kingdom classification? R. H. Whittaker.
Example 2. What is the basic unit of classification? The species.
Example 3. To which kingdom do non-green, non-photosynthetic organisms belong? Fungi.
6. Book-back questions (Samacheer Kalvi)
I. Choose the correct answer
- The characteristics essential for classification are — (a) similarities only / (b) both similarities and differences. Ans: (b) both.
- The approximate number of species on Earth is — (a) 8.7 million / (b) 1 million. Ans: (a) 8.7 million.
- The largest division of the living world is the — (a) species / (b) kingdom. Ans: (b) kingdom.
- The five-kingdom classification was proposed by — (a) Whittaker / (b) Bauhin. Ans: (a) Whittaker.
- The binomial name of the pigeon is — (a) Columba livia / (b) Homo sapiens. Ans: (a) Columba livia.
II. Fill in the blanks 6. Gaspard Bauhin introduced binomial nomenclature in 1623. 7. Species is the basic unit of classification. 8. Fungi are non-green and non-photosynthetic in nature.
III. Answer briefly 9. Name the five kingdoms. — Monera, Protista, Fungi, Plantae and Animalia. 10. What is binomial nomenclature? — A universal two-name system giving each organism a genus and a species name.
7. Common mistakes
- Mistake: Thinking only similarities matter in classification. Fix: Classification uses both similarities and differences.
- Mistake: Calling the kingdom the basic unit. Fix: The species is the basic unit; the kingdom is the largest division.
- Mistake: Putting fungi with plants because they are not animals. Fix: Fungi are non-green and non-photosynthetic, so they form their own kingdom.
8. Quick revision
- Term 2 · Ch 5 · basis of classification.
- Classification uses similarities and differences; ~8.7 million species; hierarchy kingdom → species (kingdom largest, species basic unit).
- Whittaker's five kingdoms: Monera (bacteria), Protista (unicellular eukaryotes), Fungi (non-green), Plantae, Animalia.
- Binomial nomenclature (Bauhin, 1623): genus + species names (pigeon = Columba livia).
