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.
Protists are organisms that are part of the biological kingdom called the protista. These organisms are not plants, animals, bacteria, or fungi.Protists are a very diverse group of organisms. They are basically all the organisms that don't fit into the other groups.ne major type of protist is algae. Algae are protists that perform photosynthesis. Algae are very similar to plants. They have chlorophyll and produce food using oxygen and the energy from the Sun. However, they are not considered plants because they do have specialized organs or tissues.