Question

What are three domains of life? Give examples of each domain.

Answer 1

Hint: The six kingdom classification is proposed by Carl Woese. This classification system is also known as the "Three Domains Classification" because it divides the life forms into three domains. In this classification, organisms are classified into six kingdoms and three domains.

Complete answer:
The three domains of life are Archaea, Bacteria, and Eukarya.
1. Domain Archaea: Domain archaea contains organisms which have prokaryotic cells. They lack nuclear membranes. They contain RNA markers from bacterial cells. Archaea are considered the oldest species of organisms on Earth and the term archaea is taken from the ancient Greek word which means ancient things. They have the ability to survive in extreme and harsh environments because of their specialized cell wall. The cell wall of archaea lacks peptidoglycan. 

Examples: Archaea are divided into three phyla:- Crenarchaeota, Euryarchaeota, Korarchaeota

2. Domain Bacteria: Domain bacteria also consist of prokaryotic cells. They are also called eubacteria or true bacteria. Their cell wall is made up of peptidoglycan. Their cell membrane is made by an ester linkage formation between unbranched fatty acid chains and glycerol. 

Examples: There are 5 phyla of the bacterial domain: Proteobacteria, Cyanobacteria, Eubacteria, Chlamydias, Spirochaetes

3. Domain Eukarya: The domain Eukarya contains organisms that have eukaryotic cells with membrane-bound nuclei. They may have cell walls present in them. The cell wall present in them is made up of cellulose and chitin. They do not have peptidoglycans on their cell wall. 

Examples: The domain Eukarya is divided into four kingdoms: Protista, Fungi, Plantae, and Animalia.

Note:
Carl Woese proposed a six kingdom classification of organisms. He classified the organism under Archaebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia. The kingdom Monera of five kingdom classification given by R.H. Whittaker is divided into two parts in six kingdom classification- kingdom archaebacteria and kingdom eubacteria.