<span>Oxygen is required and is used to break down nutrients , like glucose sugar they ( nutrients) are later broken down to generate ATP (energy) carbon dioxide & water . organisms can use cellular respiration including bacteria , animals, plants and fungi.
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Energy available to krill is 1500 calories
<u>Explanation:</u>
Energy produced by phytoplankton = 15,000 calories
Energy available to krill = ?
Along the food chain, only 10% of energy is transferred to the organism of higher trophic level.
Thus,
energy available to krill = 
= 1500 calories
Energy available to small fish = 
= 150 calories
Energy available to medium fish = 
= 15 calories
Energy available to large fish = 
= 1.5 calories
A) The enzyme works faster, that is my own answer is on my mind