How could the disappearance of wolves from their ecosystem affect the population of other species?

Because other animals maybe needed that animal for food and now they are gone, and because the wolf helped the environment 

Talk about the foodchain..what does the wolf eat? will this cause an overpopulation in that species if the wolf disappears-may this affect the environment in any way? For example, the disappearance of wolves from their ecosystem may cause an overpopulation of deer resulting in possible struggles to find suitable habitats and increasing competition for mating and food.

If it doesn't have a nucleus its a prokaryote