Question

The three-domain system with six kingdoms is the latest classification based on
a. Mitochondrial genes
b. Nuclear genes
c. 16S rRNA gene
d. Chloroplast genes

Answer 1

Hint: R. H. Whittaker proposed the five-kingdom classification in 1969. The classification was based on characteristics such as cell structure, reproduction, and mode of nutrition. Two kingdoms Monera and Protista were included in the five-kingdom classification. The Monera kingdoms include prokaryotic organisms, and kingdom protists include single-celled eukaryotes. Kingdom fungi have chitin in their cell walls.

Complete answer:
The Carl Woese categorised the prokaryotes into two kingdoms. These are as follows:
- Eubacteria
- Archaebacteria
These two categories are classified on the basis of the structure of 16S rRNA genes.
Carl Woese proposed three domain systems that include the eubacteria, archaebacteria, and eukaryote in 1990. The given three domains signify the three primary lines of descent.
These were commonly named as bacteria, archaea, and eukarya. Therefore, collectively these domains consist of six kingdoms.

Hence, the correct answer is option (C).

Additional information:
The Swedish botanist, Carl Linnaeus was one of the first scientists, who classified organisms into two kingdoms, plants and animals. The scientist, Ernst Haeckel, classified the organisms into three kingdoms, which are Animalia, Plantae, and Protista. Herbert Copeland included the kingdom Monera and gave the four-kingdom classification of organisms. R.H. Whittaker introduced the five kingdoms by including kingdom Fungi in the classification. Scientist Carl Woese introduced the six-kingdom classification, in which he divides bacteria into eubacteria and archaebacteria.

Note: The earliest classification was based on the uses of various organisms. This branch of the science of classifying the organism and relationship is known as systematics. Carl Linnaeus is one of the first scientists who classified organisms according to binomial nomenclature.