Which type of pathogen is single-celled and can breathe, move, and reproduce similar to multi-cellular animals?

The correct answer is protozoa, which are a group of single-celled organisms that share several characteristics commonly associated with multi-cellular animals, such as the ability to move, breathe, and reproduce. Protozoa can be found in various environments, often in water, and they exhibit a range of movements, including flagella, cilia, or ameboid motion. They are also capable of complex behaviors and can feed on organic matter, similar to some higher organisms.

Protozoa differ from bacteria, which, while also single-celled, lack the complexity and functions typically associated with animal-like behavior. Bacteria do not have membrane-bound organelles and generally do not exhibit movement in the ways that protozoa do.

Fungi are primarily multicellular (though some exist as single-celled organisms, such as yeast) and have distinct characteristics, such as a mode of nutrition that involves absorbing organic material rather than actively hunting or moving to obtain food.

Viruses, on the other hand, are not considered living organisms as they cannot breathe, move independently, or reproduce on their own; they need to infect a host cell to carry out these functions. Thus, protozoa are the most appropriate choice for the question concerning single-c