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Zorluk: KolayCause-and-Effect Relationships

When grey wolves were reintroduced to Yellowstone National Park in 1995 after a seventy-year absence, scientists anticipated changes in the ecosystem, but few predicted the profound structural shifts that followed. For decades, the local elk population had grazed unchecked, heavily consuming young willow, aspen, and cottonwood trees along valley floors. This overgrazing left riverbanks bare and highly susceptible to erosion. However, the return of wolves quickly altered elk behavior. To avoid predation, elk began avoiding open valleys and gorges where they could easily be trapped. Free from intense grazing pressure, the streamside vegetation began to regenerate rapidly, with some trees quintupling in height in just a few years. This resurgence of woody plants provided critical nesting habitat for migratory birds and, crucially, supplied beavers with the building materials needed to establish dams. The resulting beaver ponds created new wetlands, slowing river currents, reducing bank erosion, and stabilizing the channels. Ultimately, the presence of a top predator did not just manage wildlife populations; it physically reshaped the geography of the park's river systems.

Based on the passage, in what order did the events in this cause-and-effect relationship occur, starting with the initial ecological catalyst and ending with the final physical modification?

  1. 1Wolves are reintroduced to the national park after a long absence.
  2. 2Elk alter their grazing behavior, avoiding open valleys and gorges.
  3. 3Streamside trees and vegetation grow back and reach maturity.
  4. 4Beavers use the newly abundant wood to build dams, creating ponds.
  5. 5River currents slow down and banks are protected from erosion.

Cevap

The correct sequence starts with the reintroduction of wolves, followed by elk changing their grazing locations, the regeneration of streamside vegetation, the construction of dams by beavers, and finally, the stabilization of the river channels.
The correct sequence shows the direct chain of cause and effect: the return of the wolves causes the elk to change their grazing locations, which allows streamside vegetation to regrow. This regrowth provides wood for beavers to build dams, which ultimately slows the current and stabilizes the river channels.

Adım Adım Çözüm

1
Identify the initial event in the causal chain.
The return of the wolves to Yellowstone is the first event, acting as the primary catalyst.
The passage begins by describing the wolves' return as the cause of all subsequent shifts.
2
Trace the direct behavior change of the prey animal.
The elk start avoiding open valleys and gorges to escape predation by the wolves.
The passage links this behavioral shift directly to the presence of the wolves.
3
Determine the impact of the behavioral change on the environment.
Trees and streamside plants begin to regrow because they are no longer being heavily grazed.
Removing the grazing pressure is described as the direct cause of the vegetation's rapid recovery.
4
Link the plant regrowth to the animal that utilizes it.
Beavers use the newly available wood to build dams and create ponds.
The passage notes that the regenerated trees supplied the material that beavers needed.
5
Determine the final physical effect on the landscape.
The beaver dams slow the river currents and stabilize the riverbanks.
The text explains that the ponds created by the dams reduce bank erosion and stabilize the channels.

Anahtar Kavram

Identifying a multi-step linear chain of cause-and-effect relationships from a passage.
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Konular

Cause-and-Effect Relationships

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