One-celled microorganisms with both plant and animal characteristics that can exist almost anywhere.

One-celled microorganisms with both plant and animal characteristics that can exist almost anywhere.

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

Answer: (A)

Single-celled, eukaryotic organisms that behave like animals—moving, feeding by engulfing food, and living in a wide range of environments—are protozoa. This animal-like lifestyle and broad distribution fit the description of organisms that are unicellular and can be found almost anywhere. Bacteria are also single-celled, but they are prokaryotes without a true nucleus or many organelles, and they don’t display the same animal-like feeding and movement. Fungi are typically multicellular (except yeasts) and don’t exhibit animal-like locomotion or ingestion. Viruses aren’t cells at all and cannot exist independently outside a host cell. So the clue points most closely to protozoa.

Single-celled, eukaryotic organisms that behave like animals—moving, feeding by engulfing food, and living in a wide range of environments—are protozoa. This animal-like lifestyle and broad distribution fit the description of organisms that are unicellular and can be found almost anywhere. Bacteria are also single-celled, but they are prokaryotes without a true nucleus or many organelles, and they don’t display the same animal-like feeding and movement. Fungi are typically multicellular (except yeasts) and don’t exhibit animal-like locomotion or ingestion. Viruses aren’t cells at all and cannot exist independently outside a host cell. So the clue points most closely to protozoa.