1. Why a coelom?

2. Some functions of a coelom Function as a hydrostatic skeleton Facilitate movement of materials between organs and organ systems Function as a depository for excretory materials Function as a shock absorber Allow for changes in organ sizes with out negative effects on the organism

3. How could a coelom originate Gonocoel theory Excretory space

4. Origins of metamerism Metamerism=serial repetition of body parts segmented

5. Advantages of segmentation Increases body size Loss of segments doesn’t always imply loss of life Division of labor= Nature of appendages=are segmental related More effective locomotion Saving energy

6. Original appendages Outgrowths of the body wall They can have independent muscularture Also have coelomic space

7. How did it happen Flatworms Outcomes –New environment is available to the creatures –Ecologically speaking, bioturbation. aeriation