what are their different types?
Tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark
Shark
tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark 
please tell me more about jaekelopterus It is a genus of predatory eurypterid, a group of extinct aquatic arthropods. is their species still alive? UNANSWERABLE where can they be found? It lived in non-marine aquatic environments. you mentioned that these were predators, what more can you tell me about them as predators? Fully grown "Jaekelopterus" would have been apex predators in their environments and likely preyed upon smaller arthropods (including resorting to cannibalism) and early vertebrates. you mean they ate each other, but what would be the benefit? UNANSWERABLE what harm can come by eating each other? It has been shown in some studies that the risk of encountering an infected victim increases when there is a higher cannibalism rate. do you know any other species that eats each other? Aquatic ecosystems please tell me more about this Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. can you please name a few of these organisms Whales, sharks, and tuna live etc can you please describe the first one to me UNANSWERABLE can you please describe the second one to me They are characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head.
wiki:11630858
Shark [SEP] Introduction
Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth. Well-known species such as the tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark are apex predators—organisms at the top of their underwater food chain. Many shark populations are threatened by human activities.