Moving up the food chain, the energy available to the organisms decreases due to metabolic heat. (You can add the second law of thermodynamics into it, if you want)
For example, in the rules of tens, the plants start with 100% of the energy but the fi red t level consumers gain 90% of the energy due to the fact energy transfers through heat.
Because of the change is available energy, consumers at the higher levels of the food chain are forced to hunt larger amounts of prey to sub stain themselves.
