Answer:
Firstly, the grass by which the bison graze on would overgrow. It would keep growing and growing because there isn't a predator to prevent that from happening.
The predator of the bison would run out of food and thus go extinct. The predators of the predators of bison would run out of food and go extinct, as well. This would continue.
Eventually, there would be nothing but tons of overgrown grass.
