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Difficulty: MediumCause-and-Effect Relationships

Passage

In the early 1930s, Australia's lucrative sugar cane industry faced a severe threat from two native pests: the French's cane beetle and the greyback cane beetle. Desperate for a solution to protect their crops, agricultural authorities looked to Hawaii, where the central American cane toad (*Rhinella marina*) had reportedly been introduced with great success to control pest populations. Seeking to replicate these results, the Australian Bureau of Sugar Experiment Stations imported 101 young toads in 1935, breeding them and releasing thousands of offspring into the cane fields of northern Queensland. However, this biological control measure yielded unexpected consequences. The toads proved unable to jump high enough to reach the beetles, which inhabited the upper sections of the tall sugar cane stalks. Furthermore, the beetles were active during the day, whereas the toads hunted primarily at night. Instead of consuming the target pests, the toads began feeding on easier local prey. Lacking natural predators of their own in Australia and equipped with highly toxic defense mechanisms, the toad population multiplied exponentially, expanding its territory and decimating native Australian wildlife.

Based on the passage, in what order should the following events be arranged to represent the correct logical cause-and-effect sequence, starting with the initial problem and ending with the final ecological consequence?

  1. 1Native beetles threaten the economic viability of Australian sugar cane crops.
  2. 2Agricultural authorities import and release cane toads in Queensland.
  3. 3Cane toads fail to consume the target beetles due to physical and behavioral differences.
  4. 4The toad population grows uncontrollably, damaging native wildlife.

Answer

The correct logical sequence starts with the threat of native beetles to sugar cane crops, followed by the release of cane toads as a solution, then the failure of the toads to reach or hunt the beetles, and ends with the exponential growth of the toad population and the resulting damage to native wildlife.
The correct sequence logically follows the causal chain described in the text: the threat to the sugar cane crops (initial cause) led to the import and release of cane toads (effect of threat, cause of the next phase). Once released, the physical and behavioral differences between the species caused the failure of the control method (effect of release, cause of the ecological shift). Finally, the lack of predators and abundance of other prey caused the toad population to grow and destroy local wildlife (final outcome).

Step-by-Step Solution

1
Identify the initial event that started the sequence of events.
The threat to sugar cane crops by native beetles.
Agricultural authorities only sought a biological solution because the crops were in danger, making this the primary cause.
2
Determine the direct action taken in response to the initial threat.
The release of imported cane toads into the Queensland fields.
This action was a direct consequence of the search for a solution to the beetle problem.
3
Analyze why this action failed and what occurred immediately after.
The toads failed to consume the beetles due to height and time mismatches.
The lack of physical contact and different schedules between the toads and the beetles was the direct cause of the biological control's failure.
4
Identify the final ecological consequence of the failure of the biological control.
The exponential growth of the toad population and destruction of native wildlife.
Since they could not eat the beetles, the toads targeted native species, leading to unchecked population growth and ecological damage.

Key Concept

Cause-and-effect relationships and sequencing in reading comprehension
Estimated Time:1m 30s
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Topics

Cause-and-Effect Relationships

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