Which term describes organisms anchored to a substrate and do not move?

• A. Planktonic
• B. Nektonic
• C. Sessile
• D. Benthos

Answer: (C)

In marine biology, how an organism relates to its habitat and movement is used to describe its lifestyle. A sessile organism is fixed to a surface and remains stationary, which is exactly what “anchored to a substrate and do not move” describes. Examples include barnacles, oysters, and corals that attach to rocks or other surfaces and stay in place. Planktonic organisms drift with the water, nektonic organisms swim actively, and benthos covers organisms living on or near the seabed—many of these can move or extend themselves, but sessile specifically means being attached and immobile.