Difficulty: Easy

Average Score: 94%

Preserving tropical rain forests is complex. Important economic plans in Brazil called for clearing forests in order to use the land for large cattle ranches. Yet the Brazilian government wanted to preserve as much land as necessary to sustain plant and animal species. In 1976 a study was developed to determine how big a tract of rain forest must be to maintain its biological integrity. For the study, biologists cut down Brazilian rain forest to isolate tracts of various sizes: five of 1 hectare, five of 10 hectares, one of 100, two of 1,000, and one of 10,000. They identified all species in each tract before and after it was isolated. They wanted to observe which species leave or die out, and in what order, so that they could discover the minimum critical size that a species requires for its survival and how species depend on one another to survive. The project's early findings were suggestive. In rain forests, a disturbance of one species can interfere with the well-being of many others. For example, ant-following birds depend entirely on the forays of army ants to flush out other insects such as grass-hoppers and crickets. In 10-hectare plots the colonies of army ants, which in their periodic movements range over as much as 30 hectares, could not survive; deprived of the flushed insects, the birds also vanished.

Which of the following best describes the purpose of the first paragraph?

Rationale

To present evidence that demonstrates the complexity of preserving rain forests.

The first paragraph outlines the conflicting interests between economic development and environmental preservation in Brazil, illustrating the challenges faced in maintaining tropical rain forests. It introduces the study aimed at understanding the critical size needed for biological integrity, emphasizing the complexity of the issue.

A (To summarize the benefits that are inherent in preserving rain forests) YOUR ANSWER

This choice suggests a focus on the advantages of preservation; however, the paragraph does not enumerate benefits but rather highlights the challenges and conflicts surrounding forest conservation. The emphasis is on complexity, not on benefits.

B (To present evidence that demonstrates the complexity of preserving rain forests) CORRECT

This is the correct answer, as the paragraph discusses the tension between economic plans for cattle ranching and the need to preserve land for biodiversity. It underscores the intricate balance required to maintain ecological integrity amid development pressures.

C (To explain the methodology of the study) YOUR ANSWER

While the paragraph mentions the study, it does not go into detail about the methodology of the research itself. Instead, it sets the stage by discussing the broader context and motivation for the study, rather than specifically explaining how the research was conducted.

D (To describe the hypothesis on which the study is based) YOUR ANSWER

The paragraph does not clearly articulate a specific hypothesis but rather discusses the general goal of understanding the critical size for species survival. It focuses on the background and rationale behind the study rather than a testable hypothesis.

E (To suggest that the findings of the study are still inconclusive) YOUR ANSWER

This choice implies uncertainty about the study’s findings, but the paragraph does not discuss the results or their inconclusiveness. It primarily addresses the complexities involved, rather than the outcomes of the research.

Conclusion

The first paragraph effectively highlights the complexities involved in preserving tropical rain forests, emphasizing the conflicting interests between economic development and ecological integrity. By doing so, it sets the stage for understanding the importance of the study's findings, which aim to address these critical environmental issues.

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