Classification
Cnidaria are classified as Metazoa which means they are in fact an animal. They also have evolved into the Eumetazoa class which means that their tissues are specialized. This means that unlike the sponge, a single cell of this organism could not live on its own. The Cnidaria has radial or biradial symmetry. It has only one opening which serves as a mouth and the anus. They are diploblasts meaning they have two layers of cells, ectoderm and endoderm. Diversity Cnidaria is separated into 2 different broad categories. Polyps and Medusae. Examples of polyps and Medusae are sea anemones and jellyfish respectively. The animals mouth is surrounded by tentacles that have capsules called nematocysts that are used for protection but also to feed. Life History Their body has a sac-like body space where food is digested. All Cnidaria are carnivores and they usually are passive predators which mean they wait for food to get caught in their tentacles and then eat it. Cnidaria reproduce by letting larvae into the water freely where they then find the opposite sex and form a new organism called a planula occurs. Ecological Roles Polyps which are coral provide protection and a habitat for many different marine animals. Human Impacts Cnidaria are actually very relevant to our lives. Many humans are actually living on top of broken down coral islands. When coral dies and its skeleton breaks down over a long period of time it forms an island. We are endangering Cnidaria through our pollution and also are exploration of coral reefs. Many people do not know that coral is an animal, not a plant, and they step on it, or touch it in ways that damage it. |
http://www.newworldencyclopedia.org/entry/Cnidaria
http://tolweb.org/Cnidaria
http://tolweb.org/Cnidaria