One day in a big prairie field the rats lived in peace. There were green rats and white rats due to genetic variation.
The snake shows up to the club where the rats hang and have beer. This is because the rats were part of the snake’s diet.
Where’d all my food go?
The snake attacks the rats and eat them, however, it ate mostly the white ones because the green ones camouflage so well with the green grass.
Opposed to the original population, after the snake arrived their were more green rats than white rats. This messes with the original population.
There is no saving you now
The rats mating season begins and the rats have sex.
Where’s the snake at?
The snake comes back but doesn’t find as many rats to eat because the green rats had a higher chance of producing more offspring than the white rats which led to there being less white rats and more green rats.