Living World and Classification of Microbes — Science STD 8 — Question

1. The classification system that Whittaker has adapted is totally based on scientific foundation.
2. Prokaryotes are placed separately in a different kingdom. The prokaryotic organisms are different from other organisms, thus placing them separately is justified.
3. All unicellular eukaryotic organisms are clubbed together in one kingdom named, Protista. This has helped to solve the placement of Euglena.
4. Euglena has chloroplasts like plants but as animals it has flagella and thus there was conflict about such species during previous classification systems. It was placed in protozoa previously.
5. Fungi are saprophytic and hence they are placed separately in a unique kingdom.
6. According to five kingdom classification, the cell structure, organization of cell, mode of nutrition, lifestyle and phylogenetic relationship are taken into consideration.
7. Therefore the system of 5 kingdom classification becomes most authentic system of biological classification.

II. Demerits of Whittaker’s method of classification:

1. Some organisms belonging to Monera and Protista have ability to perform photosynthesis. Thus they show mode of nutrition as autotrophic, while others are heterotrophic. Similarly some monerans have cell wall and some Protists also have cell wall. This becomes confusing during their placement.

2. In kingdom Protista, organisms show varied characteristics. In spite of this they are placed together.

3. In kingdoms, Plantae, Animalia and Fungi the organisms having primitive characters and were initial examples during evolution are not included. E.g. In Kingdom Animalia, amoeba is not included though it is said to be unicellular animal. This creates confusion.

4. Similarly if algae are unicellular, they are placed in kingdom Protista and if they are multicellular they are placed in kingdom Plantae. In reality, unicellular and multicellular algae both show much similarity. But due to Whittaker’s classification system they are placed away from each other.

5. Species of algae such as Chlorella, Chlamydomonas are not included in Kingdom Protista.

6. Viruses are not included in any of the kingdoms by Whittaker. Their classification has become a point of debate among the biologists