Question

Choose the correct answers from the alternatives given.
Which of the following domains contains the most primitive bacteria that live in extreme environments?
a. Archaea
b. Plantae
c. Fungi
d. Eukarya

Answer 1

Hint: Bacteria are microscopic, single-celled organisms. They are prokaryotic, that is, do not have well defined nuclei. They are found in soil, water, human gut, etc. Some bacteria help in curdling milk to make yoghurt and some help in digestion in humans.

Complete answer:
Biologists have organized living things into separate groups called kingdoms. There is a total of six kingdoms:
• Archaebacteria
• Eubacteria
• Protista
• Fungi
• Plantae
• Animalia

Earlier, kingdom Monera was split into two groups Archaebacteria and Eubacteria. Although these two groups were different in many ways, a new level of classification was created called Domain. Now, there are three domains.
- Eubacteria
- Archaea
- Eukarya

Archaea is the domain which contains the most primitive bacteria that live in extreme environments. Some of the first archaea were found in Yellowstone National Park’s hot springs. They are either gram-negative or gram-positive bacteria. They have varied shapes such as spherical, round, spiral, lobed or pleomorphic. They multiply by binary fission, budding, or fragmentation. They are unicellular. They do not have peptidoglycan in their cell wall. Some are flagellated and some not. They have some genes that resemble that of eukaryotes. They are usually not pathogenic. They can survive in harsh temperatures.

There are three major types of archaea:
• Methanogens- these are anaerobic bacteria that produce methane. They are mostly found in sewage treatment plants, intestines of ruminants, etc.
• Halophiles- these bacteria thrive in high salt concentrations such as in salt lakes, etc.
• Thermophiles- these are heat loving bacteria. They are resistant to high temperatures and are mostly found in hot springs.

Hence, the correct answer is option (A).

Note: The other two domains eubacteria and eukarya are very much different from archaea. Eubacteria are true bacteria and have peptidoglycan in their cell wall. Eukarya are much more evolved. They have a nucleus and organelles