Dolphins are mammals, but they look very different to mammals that live on land, as they are adapted to living in water. They have a streamlined shape and fins instead of legs. They also have blowholes on the tops of their heads. They use these to breathe,rather than through their mouths and noses.
physiological adaptations relate to how the organism metabolism works. These adaptations enable the organism to regulate their bodily functions, such as breathing and temperature perform special functions like excreting chemicals as a defense mechanism.