Secondo principio della termodinamica

The second law of thermodynamics states that entropy, the amount of disorder in a system, increases each time energy is transferred or transformed. During every energy transfer, a certain amount of energy is lost in an unusable form, typically as heat. This heat energy increases the disorder and randomness of the system and its surroundings, making it progressively less organized.

When primary producers like plants receive energy from the sun and make food, a small amount of that energy is transformed into unusable heat energy, which is released along with oxygen into the environment. This heat release increases the system's entropy by adding disorder to the surroundings.

Energy is lost at each trophic level as heat and metabolic byproducts. Primary consumers harvest chemical energy from plants and release heat and carbon dioxide during metabolism. Carnivores then harvest the remaining chemical energy from herbivores, with only a fraction representing the original radiant energy from the sun.

At each stage of the food web, organisms release heat energy and other metabolic byproducts such as carbon dioxide into their surroundings. These released substances increase the disorder and randomness of the system, thereby increasing the overall entropy of the food web and demonstrating energy loss.

Heat energy released during metabolism can temporarily increase the speed of molecules it encounters in the environment. As organisms release more heat energy through metabolic processes, the system loses order and becomes increasingly random, demonstrating entropy increase throughout the biological system.

Energy decreases at each trophic level due to heat loss and metabolic processes. Primary consumers harvest chemical energy from plants but release some as heat and carbon dioxide. Carnivores receive only a fraction of the original solar energy, with additional losses occurring at their level as well.

The second law explains why energy transfer through food webs is inefficient. Each transfer results in energy loss as heat and metabolic byproducts, limiting the amount of usable energy available to higher trophic levels and demonstrating why food webs cannot sustain indefinitely without continuous solar energy input.