The snail species, (Billy Bob Joe), lives on a sandy beach. The snails are eaten by hungry birds that live above them.
More snails are made from the parents. So, that means that there are more snails that can survive. There's not a lot of food and space for them to live on. Also, some of the snails are always spotted by the birds and eaten.
Not all snails are brown. Some snails are born with different colors. Some are green, red, and blue. All the snails on the beach are all trying to stay alive from the birds.
All of the other snails that are not brown are spotted eaisly from the birds above. The brown snails are able to stay alive because of the color of their shells, they match perfectly with the environment, it makes it easier to hide. They match perfectly with the environment.
Because of the brown color on the snail shells, it makes it easier to adapt to the beach and better avoid the birds. The brown snails are eaten less often and can survive longer.
Only the surviving snails are able to get the chance to reproduce more. Because of those snails are brown, they pass down their brown color traits to their offspring. All in all, a greater percentage that there are more brown snails in the generation.