What is the relationship between propagation and density change?

Density affect propagation.

Density is mass per unit volume of a substance.

A substance that is more sense has more mass per unit volume, it will make sound to transmit at slower rate . Less dense substance will allow sound to transmit at higher rates. Density affect the speed a wave will be transmitted through it. The denser the material, the slower wave will be transmitted.

Explanation:

Density is Mass per unit volume. Density affect the propagation of wave. The denser the substance, the slower wave will be transmitted through it. The less dense the material, the higher wave will be transmitted through it. Density affect the speed of wave.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.