There are three main subclasses of gastropods; the Prosobranchia (ocean snails), Opisthobranchia (sea slugs, sea butterflies and sea hares), and Pulmonata (land and freshwater snails and slugs). Each of the subclasses has evolved in their own way and members differ in their reproduction and life cycles within the subclasses. The gastropod folks are so large it really is impossible to spell out living cycle of each one individual species, but a majority of general rules do apply. The more evolved the species, the more complex their reproductive cycle in addition to their biology. Here we will look at the life span cycle of a gastropod through various examples and how they differ with regards to the type. For instance anal sex without using any preventive measures and then proceeding to continue with normal sexual intercourse can lead to the entry of bacteria inside the urinary tract through the vaginal canal. Biologics: Biologic response modifiers used with DMARDs are genetically engineered drugs that target various protein molecules involved in the immune response. Examples include Enbrel and Remicade.