Food chains allow energy to move through an ecosystem. For example, energy is transferred from organism to organism such as the sun gives energy to grass, grass gives energy to grasshoppers when they eat grass, mice eat grasshoppers, and snakes eat mice, eagles or bigger birds of prey eat snakes. A technique discovered by Charles Elton named energy pyramids display how energy is dispersed on a pyramid starting from producers to tertiary consumers. An example of a producer would be grass, primary consumer would be a grasshopper (herbivores), a secondary consumer would be a mouse/mice (eat herbivores), and a tertiary consumer (eat secondary consumers) would be an owl. Starting from the bottom of the energy pyramid (producers) to the top (tertiary consumers) it 10% of energy is available to travel up the pyramid. That is your scientific explanation!