Which group of organisms is known for having a swim bladder for buoyancy?

The group of organisms known for possessing a swim bladder for buoyancy is fish. The swim bladder is a gas-filled organ that allows fish to maintain their depth in the water column without expending energy. By adjusting the amount of gas in the swim bladder, fish can achieve neutral buoyancy, which helps them to conserve energy while swimming and maneuvering through their aquatic environment. This adaptation is particularly important for survival, as it allows fish to effectively exploit various ecological niches and successfully evade predators or catch prey.

In contrast, amphibians primarily rely on their skin and body shape for buoyancy, as most do not have a swim bladder. Reptiles do not have swim bladders either; instead, they utilize other adaptations for buoyancy and movement in the water, like their body shape and lungs. Mammals, while some are aquatic, such as whales and dolphins, do not possess swim bladders. Instead, they rely on fat, blubber, and a streamlined body shape for buoyancy in the water. Thus, fish are uniquely characterized by their swim bladders among these groups.