Examkin

Question

Difficulty: MediumCause-and-Effect Relationships

Passage

During the nineteenth century, the intensive maritime fur trade drove sea otters to near extinction along the Pacific coast of North America. The removal of this key predator triggered a rapid cascade of ecological changes within coastal waters. Sea otters feed primarily on herbivorous invertebrates, particularly sea urchins. In the absence of otters to limit their population, sea urchin numbers swelled dramatically. These unchecked urchin populations grazed destructively on the anchoring structures, or holdfasts, of giant kelp—the massive marine algae that form dense underwater forests. Consequently, vast, productive kelp forests were decimated, replaced by barren rocky areas known as 'urchin barrens.' The disappearance of these kelp forests, which serve as critical nurseries and food sources, subsequently led to a sharp decline in local fish populations. This collapse in biodiversity ultimately devastated coastal indigenous fisheries that had relied on the diverse ecosystem for generations.

Based on the passage, arrange the following events in order to represent the chronological and logical sequence of cause and effect, starting from the initiating human action and leading to the final consequence.

  1. 1Intensive maritime fur trade targeting sea otters
  2. 2Proliferation of sea urchin populations
  3. 3Destruction of giant kelp holdfasts
  4. 4Creation of urchin barrens
  5. 5Decline in local fish populations and indigenous fisheries

Answer

The correct logical order of the causal chain is: (1) Intensive maritime fur trade targeting sea otters, (2) Proliferation of sea urchin populations, (3) Destruction of giant kelp holdfasts, (4) Creation of urchin barrens, and (5) Decline in local fish populations and indigenous fisheries.
The correct sequence traces the chronological and logical path of ecological causality described in the passage: the human fur trade decimated sea otters, which allowed sea urchins to overpopulate; the overpopulated urchins consumed the kelp holdfasts, destroying the kelp forests; the loss of these forests turned the area into rocky barrens, which ultimately deprived fish of habitat and devastated local fisheries.

Step-by-Step Solution

1
Identify the initiating cause in the passage.
Intensive maritime fur trade targeting sea otters.
The passage begins by explaining that the nineteenth-century maritime fur trade drove sea otters to near extinction, triggering the subsequent cascade.
2
Identify the immediate effect of the loss of sea otters.
Proliferation of sea urchin populations.
Since sea otters feed on sea urchins, the absence of otters meant that sea urchin numbers swelled dramatically.
3
Identify the impact of the increased sea urchin population.
Destruction of giant kelp holdfasts.
The text states that the unchecked urchin populations grazed destructively on the holdfasts of the giant kelp.
4
Identify the habitat shift resulting from the destruction of giant kelp.
Creation of urchin barrens.
As kelp forests were decimated, they were replaced by barren rocky areas known as urchin barrens.
5
Identify the ultimate consequence of this habitat shift.
Decline in local fish populations and indigenous fisheries.
The disappearance of the kelp forests (which served as nurseries and food sources) led to a sharp decline in fish populations and devastated local indigenous fisheries.

Key Concept

Tracing a multi-step chain of cause-and-effect relationships in a natural science passage.
Estimated Time:2m 0s
Rate this question

Topics

Cause-and-Effect Relationships

More questions from this topic