Final answer:
The extinction of the wolf population can lead to a decline in beaver and songbird populations due to increased herbivory by ungulates like elk, affecting vegetation crucial for these species.
Step-by-step explanation:
If the wolf population becomes extinct, two organisms that would be adversely affected are beavers and songbirds. In the case of beavers, wolves in an ecosystem like Yellowstone National Park help control elk populations. Without wolves preying on elk, the elk population can grow to levels that lead to overgrazing. This overgrazing affects the vegetation along streams and rivers, which is crucial for beavers to build their dams and lodges, thus potentially leading to a decline in the beaver population.
Similarly, songbirds would suffer from the extinction of wolves due to the trophic cascade effect. With the wolves gone, increased herbivory by elk and other ungulates would reduce the density and diversity of vegetation, which provides essential nesting sites and food sources for many songbird species. The loss of this habitat could result in the decline in songbird populations.