Register for FREE to remove ads and unlock more features! Learn more. The renin-angiotensin-aldosterone system (RAAS) is a hormone system that regulates blood pressure and water (fluid) balance . This system proceeds through several steps to produce angiotensin II, which acts to stabilize blood pressure and volume.
A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits.Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups.ish do not represent a monophyletic group, and therefore the evolution of fish is not studied as a single event. Early fish from the fossil record are represented by a group of small, jawless, armored fish known as Ostracoderms. Jawless fish lineages are mostly extinct.
Class Osteichthyes (the bony fish) is the largest class of vertebrates with over 20,000 species. The total numbers of fishes exceed that of all other kinds of vertebrates combined.obe-finned fish, the other type of bony fish, have muscular fins supported by bones. Only one species of lobe-finned fish, the coelacanth, still lives. Key features of Osteichthyes. 1  Skeleton more or less bony, vertebrae numerous. 2  Skin with mucous glands and embedded dermal scales. 3  some without scales. 4  Paired fins.