5. No body cavity to a body cavity with muscle lined organs or coelom. A coelom allows for internal organs to operate independently of each other. Cardiac muscle squeezes heart independently of muscle moving food through the digestive track.
Primitive characteristicMore recently evolved characteristic
One tissue layer or ______________or______________
_____________ ______ or ____________________and bilateral symmetry
No body cavity or _______________________
Water habitat or _______________________
_______________ _________or “tube within tube” body
No head region or _____________________