1. Open Circulatory System Blood is not always inside blood vessels Heart pumps blood into a short vessel that opens into the body spaces containing the internal organs Blood sloshes over organs and returns eventually to the heart

2. Open Circulatory System

3. Mollusks that live in water have gills Gills = organs that remove oxygen from the water Gills have cilia that move back and forth, making water flow over the gills

4. Land Snail Photo credit: NOAA

5. Aquatic Snails Photo credits: MSC

6. Slug Photo credit: NOAA

7. Banana Slug Photo credit: MSC

8. Nudibranch Photo credit: MSC

9. More Nudibranchs Photo credits: MSC

10. Bivalves --clams http://video.nationalgeographic.com/video/a nimals/invertebrates-animals/other- invertebrates/weirdest-clam-vs-world/ http://video.nationalgeographic.com/video/a nimals/invertebrates-animals/other- invertebrates/weirdest-clam-vs-world/