Natural selection is the process in which the more favorable traits due to mutation that are in a select few in a population produce more offspring then others. An example of this is bacteria resistant to antibiotics due to the faster reproduction of the resistant bacteria over the non resistant ones
Enzymes are the things in our bodies that facilitates reactions. They break down bonds in carbohydrates, lipids and proteins. When the food is being broken down, it is easier for the body to use. When the body is conducting cellular respiration, it uses monosaccharides (singular carbohydrate), to form ATP which is useable energy for the body. The body uses ATP everywhere for all bodily functions, which maintains homeostasis. <span />
They would not break and they would come to earth and crush people