Final answer:
The subclass known as Pulmonata within the phylum Mollusca and class Gastropoda includes terrestrial species like snails and slugs, which utilize a lung-like structure for respiration instead of gills.
Step-by-step explanation:
Subclass Pulmonata in Phylum Mollusca
In the phylum Mollusca, the subclass known for having species such as snails and slugs that primarily breathe using a lung-like structure is called Pulmonata. This subclass falls under the class Gastropoda. Gastropods are noted for their asymmetrical bodies and are typically distinguished by a coiled shell, although some members of this class lack shells altogether.
Unlike aquatic gastropods that use gills (ctenidia) for respiration, members of the subclass Pulmonata are primarily terrestrial and have adapted their mantle cavity into a respiratory structure that functions much like a lung, hence the name Pulmonata. This adaptation allows them to inhabit various land environments. Additionally, Gastropoda is the largest class within Mollusca, which includes several diverse forms ranging from snails to slugs to limpets.
Mollusks themselves exhibit a range of morphologies, commonly possessing a calcareous shell, although in some species, like those in Pulmonata, the shell is reduced or absent. Gastropods also feature a unique trait in the form of a radula, a specialized feeding organ used for scraping food, which is present in most members.