
Some vertebrates have developed various renal systems to deal with osmoregulation in their environments. Bony fish that live in seawater drink large amounts of seawater and use cells in gills to pump excess salt out of the body. This is in response to:

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Correct Answer: D. A need to maintain their tissues in a hypoosmotic state.
Different organisms have different needs to maintain their water balance, depending on the environment they live in. Bony fish living in saltwater maintain hypoosmotic body fluids. The hyperosmotic water they live in tends to draw the water out of their body by osmosis. They can obtain water by ingesting ocean water, but this raises their internal osmolarity. They excrete salt, then, to lower their internal osmolarity.
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