Question

Difficulty: HardDistinguishing Main Ideas from Supporting Details

The following passage describes bioluminescent signaling in certain marine organisms:

In the twilight depths of the Caribbean Sea, certain species of tiny, shelled crustaceans known as ostracods engage in a nocturnal ritual of remarkable complexity. Unlike most bioluminescent organisms, which emit light primarily to startle predators or lure prey, these male ostracods release precise, pulsing sequences of blue light into the water column. These luminous trains, lasting only a few seconds, serve as highly specific courtship signals designed to attract females of the same species. By varying the duration of the pulses, the distance between successive emissions, and the overall trajectory of the swimming path, different ostracod species are able to occupy the same geographic space without cross-species mating errors. While researchers have documented that these displays are energetically costly and increase vulnerability to visual predators like reef fish, the evolutionary pressure to secure a mate has favored the preservation of these elaborate signaling systems. Indeed, this specialized behavior represents one of the few confirmed instances of complex visual signaling in the deep ocean, illustrating how sexual selection can drive physiological and behavioral adaptations that seemingly contradict basic survival strategies.

Which of the following statements best summarizes the main idea of the passage as a whole?

  1. Sexual selection has driven the evolution of complex, species-specific bioluminescent signaling in male ostracods despite the survival risks associated with these displays.Answer
  2. B
    By varying the duration and trajectory of their light pulses, different ostracod species can inhabit the same geographic area without interbreeding.
  3. C
    Bioluminescent signals in marine environments have evolved primarily to facilitate sexual selection rather than to defend against predators.
  4. D
    Reef fish have adapted their visual systems to detect the specific pulsing frequencies of male ostracods' courtship displays.

Answer

The statement that sexual selection has driven the evolution of complex, species-specific bioluminescent signaling in male ostracods despite the survival risks associated with these displays.
The correct answer accurately summarizes the main idea of the passage. The passage explains that male ostracods use complex, species-specific bioluminescent signals to attract mates and that, despite the physical costs and predatory risks, this behavior has been preserved because of the pressure of sexual selection. This evolutionary trade-off between survival and reproduction is the central focus of the text.

Step-by-Step Solution

1
Identify the topic and scope of the passage.
The passage discusses a specific type of bioluminescent courtship behavior in male Caribbean ostracods.
Understanding the scope prevents selecting overly broad options.
2
Analyze the relationship between the details and the author's primary focus.
The author emphasizes that while the bioluminescent displays are costly and attract predators, they are maintained because they allow specific species to mate without error, illustrating how sexual selection overrides basic survival strategies.
This distinguishes the central argument from supporting details like the mechanics of the signaling or general marine bioluminescence.
3
Evaluate the options against the whole passage.
The option regarding sexual selection driving complex signaling despite survival risks captures both the courtship function and the evolutionary paradox described in the text.
The correct answer must represent the primary main idea rather than isolated details or unsupported claims.

Key Concept

Distinguishing Main Ideas from Supporting Details
Estimated Time:2m 30s
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