It can either help it or completely ruin it, you probably have/going to learn/learned it in seventh grade.
If you introduce some animals, they will completely take over the habitat, such as Snakeheads in the Chesapeake bay. When they were introduced, they completely took over the environment by rapidly reproducing and eating all of the fish. This is called an invasive species. Invasive species are exotic animals that come from another country/state. Exotic species are completely fine, they are introduced and there is nothing wrong, they may even help the environment.
Answered well enough?