Posted: May 24th, 2017

Explain why living in seawater represents an osmotic challenge to marine fishes and describe two things that marine fishes do to overcome this challenge.

Explain why living in seawater represents an osmotic challenge to marine fishes and describe two things that marine fishes do to overcome this challenge.

Example answer: The body fluids of fish are significantly less saline than seawater (about 1/3 less). Because water flows across semi-permeable membranes from lower concentrations to higher, fish must compensate for the consistent loss of water from their gills (and also through urination) by drinking seawater…. However, this increases the concentrations of salts within their bodies, so they must also actively secrete salts via their gills and urine.