Unformatted text preview: blood passes into open spaces at one point during its circulation. Most mollusks have well-developed nervous systems with large brains and sense organs. The animals have a closed digestive system with only one opening, and the system is suspended in a true coelom. All animals of the phylum Mollusca have bilateral symmetry. Three major classes make up the phylum Mollusca. The first class includes the gastropods , a group of land snails and slugs. The second class encompasses the bivalves , a group of oysters, clams, and other organisms with two shells. The third class is the cephalopods , a group of animals with numerous arms and suckers that extend from the “head foot.” Octopuses and squids are in this group....
View Full Document
- Fall '07
- Phylum Mollusca, Mollusca Members