Mollusks have many uses. Some people sell them or they raise them. The mollusk shells are used for jewelry and for decoration. Pearls are made by several speices of mollusks but mostly are made by pearl oyster. then mollusk shells provide information about the condition in the ecosystem. The internal layer shell of a cuddle fish is the cuttlebone which provides birds calcium. Squids and octopuses are able to learn tasks, so scientists are studying their nervous system to understand how learning takes place and how memory works. Mollusks are beneficial in many ways but they can also cause problems for humans. land slugs and snails can damage plants; snails are also host of parasites that harm humans. Eating infected mollusks can result in sickness or even death.