Criteria | Cartilaginous Fish | Bony Fish |
Habitat | Survive in marine, or saltwater, habitats. | Found in both saltwater and freshwater habitats. |
Gills | Gills are exposed and not protected by any external skin. | Gills are covered by an external flap of skin, known as the operculum. |
Reproduction | Reproduction occurs internally. The sperm is deposited inside of the female in order to fertilize a small number of large-sized eggs with a significant amount of yolk. | Reproduce in what is considered a primitive form of reproduction. These fish produce a large number of small eggs with very little yolk. |