Which of the following is not a domain of life? a. Bacteria b. Archaea c. Protists d. Eukarya
The Correct Answer and Explanation is:
The correct answer is: c. Protists
Explanation
In biological taxonomy, domains represent the highest level of classification in the hierarchy of life. The current system, known as the three-domain system, was proposed by Carl Woese in 1990 based on differences in ribosomal RNA (rRNA) sequences. The three recognized domains of life are:
- Bacteria – These are single-celled prokaryotic organisms that lack a nucleus. They have simple cell structures and are found in a wide variety of environments. Examples include Escherichia coli and Streptococcus.
- Archaea – Also single-celled and prokaryotic, archaea differ significantly from bacteria in their genetic makeup and biochemical processes. Many archaea thrive in extreme environments, such as hot springs, salt lakes, and deep-sea vents.
- Eukarya (or Eukaryota) – This domain includes all eukaryotic organisms, which have cells with a nucleus and other membrane-bound organelles. It encompasses four traditional kingdoms: Animals, Plants, Fungi, and Protists.
The key point here is that “Protists” are not a domain themselves. Rather, they are a diverse group of eukaryotic organisms that do not fit neatly into the other eukaryotic kingdoms. Protists include organisms such as algae, amoebas, and paramecia. They are categorized under the domain Eukarya, not as a separate domain.
Therefore, while Bacteria, Archaea, and Eukarya are the three domains of life, Protists are part of the domain Eukarya and are classified based on shared traits rather than evolutionary lineage. This makes “Protists” the correct answer to the question about which is not a domain of life.
In summary, Protists are not a domain but rather a subgroup within one of the domains (Eukarya), which is why option c is the correct choice.
