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Unformatted text preview: Bio Notes March 23 Phylum Mollusca- contains 3 well-known classes- Gastropods-Bivalves- Cephalopods Mollusks all have something in common: a foot. They also have gills, shell, mantle cavity. ---- Mollusks have an opne circulatory system.----Organs- This starts with the Platyhelminthes. Sponges have no tissues. Cnidarians have tissue but lack organs. There is also some form of circulatory system (open or closed), the reason is because there is a need for a transport system for nutrients and gases. (oxygen) An open circulatory system means that the blood does not always flow through blood vessels. We cal this hemolymph. (when there is an open circulatory system) A closed circulatory system means that it will always flow through blood vessels. Phylum Nemotoda-- “thread-like” – roundworms- they are very widespread. They have an exoskeleton which needs to be shed throughout their lives. ( Ecolysis) – R- strategists?- many feed on bacteria.- transient resources Not all of them are R-...
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- Spring '12
- opne circulatory system.