how could the disappearance of wolves from their ecosystem affect the populations of other species

Because the whatever the wolves use to eat that population would rise, while whatever ate the wolves would decrease making the ecosystem un balanced.

Wolves are carnivores. If they were endangered than the population of what Wolves eat would grow. Soon, it would become chaos. Ex. Too much wild hare, what would you do? Also, when the population of the non carnivores grow, they will continuously eat plants. Soon, we won't have any plants left. That's why the ecosystem has a system.