Which statement about bacteria is TRUE? A) Bacteria are in a domain of their own. B) Bacteria do not use the same genetic code as organisms in other domains. C) Archaea belong to the same domain. D) All bacteria are multicellular organisms.
The Correct Answer and Explanation is:
Correct Answer: A) Bacteria are in a domain of their own.
Bacteria are classified under their own distinct domain called Bacteria, one of the three domains of life. The three-domain system, developed by Carl Woese in the late 20th century, includes Bacteria, Archaea, and Eukarya. This system is based on differences in the sequences of ribosomal RNA (rRNA) genes, which are critical for understanding evolutionary relationships.
The domain Bacteria includes prokaryotic organisms, which means they do not have a membrane-bound nucleus or other membrane-bound organelles. Their DNA is typically found in a single, circular chromosome in the cytoplasm. Bacteria are incredibly diverse and inhabit nearly every environment on Earth, from soil and water to the human gut. Some are beneficial, such as those involved in digestion and nitrogen fixation, while others can be pathogenic, causing diseases.
Let’s address the other choices to clarify why they are incorrect:
- B) Bacteria do not use the same genetic code as organisms in other domains – This is false. All known living organisms, including bacteria, archaea, and eukaryotes, use the same universal genetic code, with very few exceptions. This shared genetic code supports the idea of a common origin of life.
- C) Archaea belong to the same domain – This is incorrect. Archaea are similar to bacteria in that they are also prokaryotic, but they belong to a separate domain called Archaea, which differs significantly in genetic, biochemical, and structural ways.
- D) All bacteria are multicellular organisms – This is false. Bacteria are unicellular organisms. While some may form colonies or biofilms, they do not form true multicellular organisms with specialized cells.
In summary, bacteria are indeed in a domain of their own, separate from Archaea and Eukarya, making Option A the correct and true statement.
