As time progresses, animals have become bigger and display more of a complex body. In some cases, this is not always true. The Poriferas and Cnidarians do not have a difficult structure like the Platyhelminthes. The body structures can determine a lot about how these animals survive in their environment, and it is important that their structure can manage their distribution of gases, and obtain food and waste. These facts and information will show proof of the many characteristics and bodily functions