Question

Discuss how classification systems have undergone several changes over a period of time?

Answer 1

1. The scientific process of grouping organisms into hierarchical groups and subgroups based on similarities and differences between them is known as biological classification. Scientists have created various classification systems, and these schemes have undergone numerous revisions over time.
2. Aristotle had created an artificial classification scheme that separated plants and animals according to their habitat. For instance, aquatic (fish, whale), terrestrial (cattle, reptiles), and aerial (birds, bats) are some examples.
3. Then, morphology, anatomy, physiology, reproduction, ontogeny, cytochemistry, and other factors served as the foundation for the natural classification system.
4. Following the natural system, creatures were categorised using the phylogenetic system, which was based on evolutionary relationships. Its foundations include cladistic taxonomy, numerical taxonomy, chemotaxonomy, and cytotaxonomy.

Answer 2

The classification systems have undergone several changes with time. The first attempt of classification was made by Aristotle. He classified plants as herbs, shrubs, and trees. Animals, on the other hand, were classified on the basis of presence or absence of red blood cells. This system of classification failed to classify all the known organisms.

Therefore, Linnaeus gave a two kingdom system of classification. It consists of kingdom Plantae and kingdom Animalia. However, this system did not differentiate between unicellular and multicellular organisms and between eukaryotes and prokaryotes. Therefore, there were large numbers of organisms that could not be classified under the two kingdoms.

To solve these problems, a five kingdom system of classification was proposed by R.H Whittaker in 1969. On the basis of characteristics, such as cell structure, mode of nutrition, presence of cell wall, etc., five kingdoms, Monera, Protista, Fungi, Plantae, and Animalia were formed.