Zooplankton are a group of tiny, usually microscopic, animals that drift in the water column of oceans, seas, and freshwater bodies. They are an essential component of the aquatic food web, serving as a link between phytoplankton (microscopic plants) and larger animals.

Characteristics:

1. _Microscopic size_: Typically ranging from 0.2 to 5 millimeters in length.
2. _Drifting lifestyle_: Zooplankton are mostly unable to swim against currents and drift with the water.
3. _Animalian nature_: Zooplankton are heterotrophic, meaning they consume other organisms or organic matter for energy.
4. _Diverse group_: Includes various species, such as crustaceans (e.g., copepods, krill), mollusks, fish larvae, and protozoa.

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