In the given ecosystem, the animal whose absence would have the greatest negative effect is the wolf.
Here's why:
- Wolves are apex predators: They control the populations of both deer and foxes, helping to maintain a balance in the ecosystem.
- Impact on other species: Without wolves, the populations of deer and foxes could increase significantly, leading to overgrazing and depletion of vegetation, which in turn affects other species in the ecosystem.
- Predation on multiple species: Wolves directly influence the populations of both deer and foxes, and their absence would disrupt these relationships.
Thus, the removal of wolves would likely create a cascading effect that could destabilize the entire ecosystem.