Which term refers to a single-celled, microscopic organism?

Which term refers to a single-celled, microscopic organism?

• A. Bacterium
• B. Virus
• C. Fungus
• D. Algae

Answer: (A)

Think about what defines a single-celled microorganism. Bacteria are classic single-celled microbes. They’re prokaryotic cells, meaning one cell carries all the necessary life functions, they’re microscopic, and they reproduce as individual units. Viruses aren’t cells at all; they’re tiny genetic packets that need living host cells to replicate, so they don’t fit the single-celled organism idea. Fungi are typically multicellular organisms made of hyphae, though some forms are single-celled yeasts—still, they’re usually discussed as a group rather than as single-celled organisms. Algae can be unicellular or multicellular, but the everyday term used for a truly single-celled microscopic organism is bacterium.

Think about what defines a single-celled microorganism. Bacteria are classic single-celled microbes. They’re prokaryotic cells, meaning one cell carries all the necessary life functions, they’re microscopic, and they reproduce as individual units.

Viruses aren’t cells at all; they’re tiny genetic packets that need living host cells to replicate, so they don’t fit the single-celled organism idea. Fungi are typically multicellular organisms made of hyphae, though some forms are single-celled yeasts—still, they’re usually discussed as a group rather than as single-celled organisms. Algae can be unicellular or multicellular, but the everyday term used for a truly single-celled microscopic organism is bacterium.