The phylum cnidaria contains a wide variety of animals that live in an aquatic setting. The animals in this phylum do not have real circulatory system. It is water based just as phylum profiera's circulatory system is. The water around the animals contains oxygen and nutrients, so the cells that touch the water take in these items. That is how they get what they need into their body. Phylum Cndaria is different from phylum profiera because the animals in this phylum do not have pores; they just have cells to come in contact with the water. Three animals in phylum cndaria are:
Jellyfish are aquatic animals that are found mostly in marine settings, but some are in fresh water. The jellyfish does not have a specialized circulatory system. It has a very thin layer of covering, so oxygen and nutrients can be easily absorbed and spread through their bodies. The cells on the top of their bodies absorb the nutrients needed to be spread around their body. Nutrients are absorbed into the gastrovascualr cavity, and then they are spread from the gastrodermis to the mesoglea and on to the epidermis.
The hydra lives in fresh water. Hydra have a circulatory system that is similar to jellyfish. They have a fluid filled gastrovascular cavity where nutrients are absorbed. The hydra gets it oxygen from the water that entered the cavity and it gets rid of carbon dioxide through this cavity. The cells lining this cavity get nutrients for the body.
Sea Anemones do not have a true circulatory system jsut as jellyfish, and hydra do not. The sea anemones stomachs serve as their circulatory system. It has a gastrovascular system like the jellyfish and hydra do. Nutrients are taken in through this cavity and they are spread through the cells lining this cavity. Waste is expelled out through this cavity also. Different animals live in anemones symbiotically, so this helps give sea anemones better circulation.