A food chain is the interaction and tranfer of energy between organisms within an ecosystem and contains multiple feeding levels.

In the case of a desert, there are four feeding levels. The primary producers, primary consumers, secondary/ tertiary consumers, and apex predators

The primary producers are usually plants which photosynthesize.

The primary consumers are usually insects, small critters, and herbivores

The secondary consumers and tertiary predators are bigger than the previous feeding level creatures, which are omnivores and carnivores

The apex predators are carniores and eat the secondary consumers.

https://prezi.com/p/od2ywx0dmfa1/apes-sahara-desert-food-web/