Final answer:
Plankton is composed of eukaryotic microbes, including algae (phytoplankton) and protozoa, but not typically fungi. Algae in plankton photosynthesize, while protozoa may be motile microorganisms.
Step-by-step explanation:
Plankton consists of tiny aquatic organisms that drift in water bodies and are primarily composed of two types of eukaryotic microbes: algae and protozoa, with algae belonging to the group known as phytoplankton. While there are eukaryotic microbes such as fungi, they are not typically considered plankton.
Planktonic fungi can occur, but when referring to plankton, it commonly includes phytoplankton, such as diatoms and dinoflagellates which are types of algae, and zooplankton, which feed on phytoplankton and other microscopic marine life. Algae are plant-like organisms that can be either unicellular or multicellular and extract energy through photosynthesis. Protozoa are primarily unicellular, motile organisms with complex cell structures.