Which of the following is a unicellular organism?

Bacteria are a prime example of unicellular organisms. They consist of a single cell that carries out all necessary life processes, including metabolism, reproduction, and response to the environment. While some bacteria can form colonies, each individual bacterium operates independently as a single-celled organism. This characteristic distinguishes them from fungi, plants, and animals, which are multicellular organisms composed of multiple cells working together in organized structures. Fungi can exist in unicellular forms, such as yeast, but they are primarily known for their multicellular forms. Plants and animals, on the other hand, are inherently multicellular, relying on complex interactions among their cells to function as complete organisms. Understanding the defining features of different types of organisms helps clarify their classification and biological roles.