Passage: In the early 1900s, wolf numbers in Yellowstone National Park were in decline. The wolves were a threat to livestock that grazed in the area. So, hunters tracked and killed the wolves until, by the 1920s, there were not many left in the area. Wolves are an apex predator, or top predator. So the shortage of wolves had a significant effect on the entire ecosystem. For example, elk and deer--prey for the wolves--increased in numbers. As these populations increased, they needed more food. And without the wolves pursuing them, they stayed in one place longer, rather than moving on. Deer were more likely to take their time browsing, stripping an area of its plant life more thoroughly. Deer eat grasses and trees, so grassy areas disappeared and tree growth was stunted. Elk love to munch on willow saplings. Beavers in the area depended on willow saplings as a food source. Eventually there were not enough of these trees to support the beaver population, and beaver populations declined. Wolves were reintroduced to the park in the 1990s. With wolves back in pursuit, elk and deer moved more quickly through the region once more. This allowed the trees and grasses to thrive again. This, in turn, led to the recovery of beaver populations. Beaver dams provide habitat for animals such as otters and fish. Recovery of wolves led to a recovery of bird populations that rely on small trees to nest. Bear populations also recovered, as berry-bearing bushes grew back.
Questions: What happened to Yellowstone National Park when wolves disappeared?(1 point) Responses The bear population increased. The bear population increased. The deer population increased. The deer population increased. The grassy areas increased. The grassy areas increased. The willow tree population increased.
How did the reintroduction of wolves to Yellowstone National Park affect the beaver population?(1 point) Responses The wolves increased the population by eating beavers’ predators. T he wolves increased the population by eating beavers ’ predators. The wolves decreased the population by eating beavers’ prey. T he wolves decreased the population by eating beavers’ prey. The wolves increased the population by eating a competitor. T he wolves increased the population by eating a competitor. The wolves decreased the population by eating beavers.
Which food source’s scarcity caused the Yellowstone National Park beaver population to decrease?(1 point) Responses grass grass willow willow fish fish otter
What happens to an ecosystem when the primary consumers disappear?(1 point) Responses The producer population decreases, while the secondary consumer population increases. The producer population decreases, while the secondary consumer population increases. The producer population increases, while the secondary consumer population decreases. The producer population increases, while the secondary consumer population decreases. Both the producer and secondary consumer populations increase. Both the producer and secondary consumer populations increase. Both the producer and secondary consumer populations decrease.
The producer population decreases, while the secondary consumer population increases.
Answer all questions
1. When wolves disappeared from Yellowstone National Park, the deer population increased.
2. The reintroduction of wolves to Yellowstone National Park decreased the beaver population by eating beavers' prey.
3. The scarcity of willow trees caused the Yellowstone National Park beaver population to decrease.
4. When the primary consumers disappear from an ecosystem, both the producer and secondary consumer populations decrease.