Which of the following contributions to the theory of the conservation of energy is an observation of a biological system?
a. julius von mayer’s observation that vibration increases the temperature of water
b. james prescott joule’s observation that the potential energy of a weight can be converted into heat energy
c. hermann von helmholtz’s demonstrations that energy is converted but not created when animal muscles move
d. baron kelvin’s hypothesis that the melting point of ice decreases as pressure decreases

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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.