Genetic Variation: The genetic Variation in the snake population is that there are snakes that are the color red and snakes that are the color yellow.
Overproduction & the Struggle for Existence: Yellow snakes are producing more offspring but most won't survive. Yellow snakes are struggling to survive because they don't blend into their environment as well as green snakes and they are getting eaten by falcons.
Differential Survival & Reproduction: The green snakes have a higher chance of surviving because they can blend into their environment. Due to the fact they have a higher chance of survival they will have a higher fitness.
Changes in the Gene Pool: Over time there will be a change in their color. The green snakes will become more common in the snake population. This will help the the snakes blend into their environment and survive.