Which term denotes small free-floating animals in aquatic ecosystems?

Which term denotes small free-floating animals in aquatic ecosystems?

• A. Agnatha
• B. Thallus
• C. Rhodophyta
• D. Zooplankton

Answer: (D)

Zooplankton are small free-floating animals in aquatic ecosystems. They drift with currents rather than actively swimming against them, which places them among the plankton. This group includes tiny crustaceans such as copepods, as well as many larval stages of larger animals and some jellyfish, all of which rely on passive movement or gentle currents to stay in the water column. They play a key role in the food web by feeding on microscopic plants and algae (and sometimes other small zooplankton) and in turn being eaten by larger suspension feeders and fish. The other terms describe plant-like organisms or larger animals, not small free-floating animals: one is jawless fishes, another is the body of a seaweed-like organism, and the last is red algae.

Zooplankton are small free-floating animals in aquatic ecosystems. They drift with currents rather than actively swimming against them, which places them among the plankton. This group includes tiny crustaceans such as copepods, as well as many larval stages of larger animals and some jellyfish, all of which rely on passive movement or gentle currents to stay in the water column. They play a key role in the food web by feeding on microscopic plants and algae (and sometimes other small zooplankton) and in turn being eaten by larger suspension feeders and fish. The other terms describe plant-like organisms or larger animals, not small free-floating animals: one is jawless fishes, another is the body of a seaweed-like organism, and the last is red algae.