Which term describes microscopic, one-celled animals often found in decayed materials and contaminated water?

Which term describes microscopic, one-celled animals often found in decayed materials and contaminated water?

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

Answer: (A)

Protozoa are microscopic, single-celled organisms that behave like animals. They typically inhabit water or decaying materials and feed on other microorganisms or organic matter, moving by structures such as pseudopods, cilia, or flagella, which gives them an animal-like lifestyle. Bacteria are also tiny and single-celled but are prokaryotes, lacking the defined nucleus and complex cell structure protozoa have. Viruses aren’t cells at all and need a host to reproduce, so they don’t fit the idea of a living single cell. Fungi can be multicellular or, in some cases like yeasts, single-celled, but they are organized differently from protozoa and don’t exhibit the same animal-like behavior. Because of these characteristics, the best term for these organisms is protozoa.

Protozoa are microscopic, single-celled organisms that behave like animals. They typically inhabit water or decaying materials and feed on other microorganisms or organic matter, moving by structures such as pseudopods, cilia, or flagella, which gives them an animal-like lifestyle. Bacteria are also tiny and single-celled but are prokaryotes, lacking the defined nucleus and complex cell structure protozoa have. Viruses aren’t cells at all and need a host to reproduce, so they don’t fit the idea of a living single cell. Fungi can be multicellular or, in some cases like yeasts, single-celled, but they are organized differently from protozoa and don’t exhibit the same animal-like behavior. Because of these characteristics, the best term for these organisms is protozoa.