Principle #1 - Genetic Variation In the black-tailed jackrabbit species, there are some differences in the phenotype , such as the brown colored rabbit, and the light-tan colored rabbit.
Principal #2 - Overproduction and the Struggle for Existence Overtime, the black-tailed jackrabbit will produce more offspring that the environment can support, which will cause some of the rabbits to die.
Principle #3 - Differential Survival and Reproduction During the night-time in the desert, the light-tan colored rabbit in the dark dirt/sand is more noticeable to the owl to capture, than the dark colored rabbit, which can be harder, because it can blend more to to it's dark dirt/sand.
Principle #3 - Differential Survival and Reproduction Sense the dark-colored rabbit is less noticeable to the owl, it will less likely be eaten, which will result in a higher fitness than the light-tan colored rabbit. Allowing the dark-colored rabbit to survive long enough to reproduce, creating more new offsprings.
Principle #4 - Changes in Gene Pool Sense the dark-colored rabbits has a higher fitness, than the light-colored rabbits, over time, the dark color allele for rabbits will increase in the gene pool, as will as the frequency of dark-colored rabbits.
These are the four important principles that make up Natural Selection.