what is this first creature you just mentioned?
Plankton are the diverse collection of organisms that live in large bodies of water and are unable to swim against a current.
Plankton
Plankton are the diverse collection of organisms that live in large bodies of water and are unable to swim against a current. 
why are certain traits adaptations in one ecosystem but not in another apex UNANSWERABLE which species are present in an apex? Gray wolf why is it present under the apex list? They often kept animals from grazing in riparian areas, which protected beavers from having their food sources encroached upon. which animals fall under the non-apex category? Sea urchins, mussels, and other shellfish. where is the last mentioned animal mostly found? Most kinds of shellfish are harvested from saltwater environments, some are found in freshwater. can they be poisonous? Shellfish caught in Alaska can lead to paralytic shellfish poisoning (PSP). does it cause any reaction when consumed by some people? It can lead to death by paralyzing the breathing muscles. what is the nutrition value of the second mentioned animal? UNANSWERABLE what does the second animal that is mentioned above, feed on? Plankton and other microscopic sea creatures which are free-floating in seawater.
wiki:25690508
Plankton [SEP] Introduction
Plankton are the diverse collection of organisms that live in large bodies of water and are unable to swim against a current. The individual organisms constituting plankton are called plankters. They provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish and whales. Planktonic organisms include bacteria, archaea, algae, protozoa and drifting or floating animals that inhabit—for example—the pelagic zone of oceans, seas, or bodies of fresh water. Essentially, plankton are defined by their ecological niche rather than any phylogenetic or taxonomic classification. Though many planktonic species are microscopic in size, "plankton" includes organisms over a wide range of sizes, including large organisms such as jellyfish.