What is defined as free-swimming organisms in aquatic environments?

The term that defines free-swimming organisms in aquatic environments is "nekton." Nekton includes a variety of species, such as fish, marine mammals, and squid, that can actively swim and move against currents. These organisms are typically larger than plankton and have a more developed swimming mechanism, allowing them to inhabit a range of aquatic environments, from oceans to freshwater bodies. This ability to swim freely distinguishes nekton from other aquatic organisms that may be more sedentary or reliant on water currents for movement.

In contrast, plankton refers to tiny organisms that drift or float in the water column, while benthos describes organisms that live on or in the seabed. Zebras, being terrestrial animals, do not fit the context of aquatic environments. Understanding these classifications helps clarify the dynamics of aquatic ecosystems and the roles different organisms play within them.