Marine v. Fresh

Diffusion/Osmosis in Fish

Today we had a discussion on how marine fish differ from freshwater fish in terms of what challenges they face in ion concentrations. Marine fish live in waters with high salinity. In order to maintain appropriate levels of water and salt they: 1) drink water 2)absorb water 3)excrete salt through gills and gut and 4) have high concentrations of salt in their urine. Freshwater fish on the other hand: 1) do not drink water 2) they absorb salt through skin and gills and 3) have very dilute urine.
Organisms from different habitats face different challenges. The marine fish needs to absorb water and get rid of salt. Freshwater fish need to absorb salt and get rid of water.