Assignment:
Some animals live in freshwater and some in saltwater. What are the different challenges in terms of osmoregulation that these two groups of animals face? Describe the physiological mechanisms that they use to solve the challenges that living in either fresh or seawater causes. (You can't describe every single physiological mechanism so choose some and describe just those. You could limit your essay to fish or you could add in other types of animals too - that's up to you.)