The dry environment of desert regions limits the organisms that can live there. Thus, the organisms, their presence, parts, interaction, and wastes are all biotic factors. If an ecosystem is to be self-sustaining it must contain a flow of energy. Those life activities that are characteristic of living organisms require an expediture of energy. The pathways of energy through the living components of an ecosystem are represented by food chains and food webs.
Producers convert the radiant energy of the sun into the chemical energy of food.
Since practically all organisms may be consumed by more than one species, many interactions occur along the food chains of any community. Through decomposition, chemical substances are returned to the environment where they can be used by other living organisms. There is a decrease in the overall energy in each level as you move up the food pyramid . This means that there is much more energy in the producer level in a food web than at the consumer levels. Also, this means that there is more energy at the primary consumer level than at the secondary consumer level.