Cnidaria are very diverse from one another. Yet, all of these diverse animals are armed with stinging cells. These stinging cells have been inherited from a common ancestor. The name Cnidaria comes from the Greek word “cnidos,” meaning stinging nettle. Many thousand cnidarian species inhabit the world’s oceans ranging from the tropics to the poles and the bottom of the ocean to the surface.
Cnidaria do not have a circulatory system because it is not needed for them. All of their cells are in contact with the water, which contains oxygen and nutrients that they need to survive. Instead of having pores like the Porifera, the cells use diffusion to transport the oxygen, nutrients, and waste in and out of the body. Cnidaria also have very intricate digestive tracts which are responsible for the transportation of nutrients to the cells.
Cnidaria do not have a circulatory system because it is not needed for them. All of their cells are in contact with the water, which contains oxygen and nutrients that they need to survive. Instead of having pores like the Porifera, the cells use diffusion to transport the oxygen, nutrients, and waste in and out of the body. Cnidaria also have very intricate digestive tracts which are responsible for the transportation of nutrients to the cells.