Which group of organisms is best described as unicellular prokaryotes that live in extreme environments?

• A. Protozoa
• B. Bacteria
• C. Fungi
• D. Archaea

Answer: (D)

Verified step by step guidance

1. Understand the key terms in the question: 'unicellular prokaryotes' means organisms made of a single cell without a nucleus, and 'extreme environments' refers to habitats like hot springs, salt lakes, or acidic conditions.
2. Recall the characteristics of each group: Protozoa are unicellular eukaryotes, Bacteria are unicellular prokaryotes but mostly live in common environments, Fungi are mostly multicellular eukaryotes, and Archaea are unicellular prokaryotes known for thriving in extreme environments.
3. Identify that the question asks specifically for unicellular prokaryotes adapted to extreme environments, which excludes eukaryotes (Protozoa and Fungi) and typical bacteria that do not specialize in extreme habitats.
4. Match the description to Archaea, as they are unique prokaryotes that often inhabit extreme conditions such as high temperature, salinity, or acidity.
5. Conclude that the best answer is Archaea because they fit both criteria: unicellular prokaryotes and extremophiles.