How can an organism's environment affect its traits?

First, I read that so incorrectly. Awkward.

An organism's environment affects its physical and self traits by making them adapt. Charles Darwin had discovered this theory with the finches. Places that were harder to get food would make these finches physical change over evolution to help them survive. It changes the animals habits depending on their resources. If a bird eats berries but there is no berries then the bird will have to change its diet or it will die.