AP BIOLOGY

Detailed explanation-1: -Microorganisms can be unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). They include bacteria, archaea, fungi, protozoa, algae, and viruses. Bacteria are single celled microbes that lack a nucleus.

Detailed explanation-2: -Many bacteria have a multicellular phase of their lifecycle, which fall into three broad categories based on shape and mechanism of formation. A number of pressures may have selected for multicellularity, including physicochemical stress, nutrient scarcity, predation, and environmental variability.

Detailed explanation-3: -While prokaryotes are always unicellular organisms, eukaryotes can be either unicellular or multicellular.