Why is energy lost when herbivores eat primary producers?

A food chain showing how each living things which are present on the planet getting food. Plants are known as producer because they have ability to use a light energy comes from sun to produce, food. Animals are not able to make their food so, they are eating other animals, and plants. They are known as consumers.

In a food chain, energy is converted from one link to another link. In a food chain when a herbivore eats food it gets a fraction of energy from plant becomes new body mass. The left energy used by the herbivores for life processes such as reproduction, digestion, and movement or lost as a waste. When the carnivore eats herbivores it passes a small amount of energy to the carnivores, and same as herbivores some energy is used for life processes or some energy is wasted.

Because of the lots of energy is wasting at each link the actual amount of energy which is transferred decreases every time.