Final answer:
If the diagram indicates water moving into the fish and the expulsion of dilute urine, then the fish is likely a freshwater fish as it needs to expel excess water due to its hypotonic environment. Conversely, if the fish is shown expelling salt and producing concentrated urine, it is likely a saltwater fish adapting to a hypertonic environment.
Step-by-step explanation:
From the information provided, we can infer that a fish that lives in saltwater will have to deal with the high salinity of its environment which is hypertonic to its cells. The fish will need to expend energy to expel excess salt through specialized cells in their gills and produce highly concentrated urine. This is done to deal with osmosis, which would otherwise cause the fish to lose too much water and dehydrate. Conversely, freshwater fish reside in water that is hypotonic to their cells. These fish need to actively take in salts through their gills and produce copious amounts of diluted urine to rid themselves of the excess water that enters their bodies through osmosis.
If the diagram shows water moving into the fish and the fish expelling diluted urine, it is likely a freshwater fish, because this is the mechanism they use to rid their bodies of excess water and maintain osmotic balance. On the other hand, if the diagram shows the fish expelling salt through its gills and excreting concentrated urine, then it is likely a saltwater fish as these adaptations help it to preserve water and regulate salt levels in a hypertonic environment.