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.
Skates and Rays. Cartilaginous fish (scientific name Chondrichthyes) have a skeleton made from cartilage instead of bone. Cartilage is tough and flexible and provides enough structural support to allow these fish to grow to very large sizes. Cartilaginous fish include sharks, rays, skates and chimaeras.There are approximately 600 different species of rays and skates and about 500 shark species. Rays and skates live in oceans throughout the world. Most rays and skates live on the bottom of the ocean while some live in open water.artilage is tough and flexible and provides enough structural support to allow these fish to grow to very large sizes. Cartilaginous fish include sharks, rays, skates and chimaeras. There are approximately 600 different species of rays and skates and about 500 shark species.