Trace back to their actual location of production your foods for today. Figure out how much energy, how many people, trucks, planes, etc were required to serve you breakfast, lunch or dinner. Check out just how much food we throw away after each meal. Figure out its caloric value and estimate how many people it might have fed. More offspring are produced than can survive to reproductive age.
Offspring vary in heritable characteristics of form and behavior.
Some of these variations improve, some lessen, an offspring's survival chances. Those offspring with beneficial traits will outproduce those with detrimental traits. The result of this diffrential reproduction is natural selection. Go out and find examples that support these various steps. Look for seeds, for overcrowded offspring, for competing offspring, etc.