Explain why the number of organisms decreases along the food chain.

Not all energy is transferred between different levels of the food chain due to not all the organisms being consumed, often not the entire organism is eaten either, leaving behind energy in the hair/fur, teeth, and bones of the prey. Furthermore energy is lost through respiration and by movement. Energy is also lost in the form of undigested nutrients in faeces and urine and therefore predators cannot consume enough energy to sustain as large populations as their prey.