Microorganisms
may be single-celled like bacteria, some algae and protozoa, or
multicellular such as algae and fungi. They can survive under all types
of environment, ranging from ice cold climate to hot springs and deserts
to marshy lands. They are also found inside the bodies of animals
including humans. Some microorganisms grow on other organisms while
others exist freely. Microorganisms like amoeba can live alone, while
fungi and bacteria may live in colonies.