1. Cnidarians comes from the Greek word "cnidos", which means stinging nettle. 2. Cnidarians, a phylum, consists of hydras, jellyfishes, sea anemones and corals. 3. Most cnidarians live in the world's oceans. 4. Some cnidarians live in fresh water. 5. Cnidarians have a body made of an outer epidermis, an inner gastro dermis, and a middle jellylike layer called the maculae. 6. The cells are organized into true tissues. 7. The body of a cnidarians is a sack with an opening. 8. This opening is surrounded by a lot of tentacles. The tentacles have nematocysts, or stinging cells. Nematocysts contain poison arrows to catch food.

Bothersome hydras, jellyfish, sea anemones, tube anemones, reef and non- reef-building corals, soft and hard, black, horny and stony, sea pens, sea pansies, sea wasps, Portuguese men of war and sea fans; these are the stinging-celled animals, the Cnidaria. These organisms are radially symmetrical (hence inclusion in a sub-Animal Kingdom, the Radiata), are made up of two basic tissue layers and possess salient "stinging" cells. These are grouped as thread-like (volvent) barbed/spined with and without toxins (penetrant), and "sticky" for anchoring (agglutinant). Their body shapes come in two basic formats; a sessile polyp-like and free- swimming medusa-like (illustration). The basic features of these body-types are evident; most species are either one or the other, medusoid or polypoid, others pass through both in their life cycle. The body cavity formed by the tissue layers bears series of tentacles around a single body/mouth/"anus" opening/mouth. There are few freshwater members (e.g. Hydras), most are marine in shallow tropical waters, though they are found worldwide at all depths. There are some ten thousand described species with a rich fossil history dating back before the Cambrian period.

1)Cnidarians usually eat fish that they stun with their tentacles

Nervous SystemDigestive System The Cnidarians have a simple nervous system called the nerve net. In the center of the nerve net is the nerve ring which controls swimming, and where to go. The nerve ring is not a brian. Therefore, cnidarians do not think or plan the same way as other animals do. The cindarian's body is made up of two layers of cells. The cnidarian's nerve cells help to coordinate the work of other body cells that are linked in the net. If it is touched the whole body reacts. All cniadarians have tentacles that have stinging cells at the ends of them. Inside of all cnidarians is a hollow bag- like cavity with one opening at the end where food and water come in and the wastes leave. Food is partially digested within the cavity. The cells take food chemicals and oxygen from the water. Cnidarians eat food through their mouth. From the mouth the food goes to the digestive cavity. Algae in the digestive cavity release oxygen into the body

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