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Difficulty: MediumStrengthen

Marine biologist: The newly discovered deep-sea sponge Cladorhiza ventis inhabits waters near hydrothermal vents. Unlike most deep-sea sponges, C. ventis entirely lacks the internal canal systems and pores required for filter-feeding on suspended organic matter. Furthermore, the surrounding water is nearly devoid of the zooplankton that carnivorous sponges typically prey upon. Consequently, it is highly likely that C. ventis relies exclusively on symbiotic chemosynthetic bacteria for its nutritional needs.

Which of the following statements, if true, would strengthen the marine biologist's conclusion? (Select all that apply)

  1. Isotopic analysis of C. ventis tissues reveals carbon signatures that are identical to those produced by known vent-dwelling chemosynthetic bacteria.Answer
  2. Laboratory observations of C. ventis show that the sponge rapidly deteriorates and starves when exposed to antibiotics that target and eliminate chemosynthetic bacteria.Answer
  3. C
    Most sponges found near hydrothermal vents are capable of absorbing dissolved organic compounds directly through their outer cellular layers without the need for pores.
  4. D
    Hydrothermal vents provide a consistently warm environment that promotes faster cellular growth rates in C. ventis than in typical filter-feeding deep-sea sponges.
  5. E
    The lack of internal canal systems in C. ventis makes it more vulnerable to certain deep-sea predators than traditional filter-feeding sponges.

Answer

The correct options are the statement regarding isotopic analysis matching bacterial carbon signatures, and the statement showing that the sponge starves when exposed to bacteria-killing antibiotics.
The argument concludes that a specific sponge relies entirely on bacteria because it lacks the mechanisms for other known feeding methods. To strengthen this, we must either show direct evidence that the bacteria provide nutrition or show that without the bacteria, the sponge cannot survive. The statement about identical carbon signatures provides direct physical evidence that the sponge's body is built from bacterial byproducts. The statement regarding antibiotics demonstrates that eliminating the bacteria leads to starvation, proving the bacteria are essential for the sponge's survival. Both independently bolster the likelihood of the conclusion.

Step-by-Step Solution

1
Identify the main conclusion.
The conclusion is that C. ventis relies exclusively on symbiotic chemosynthetic bacteria for its nutritional needs.
This is the primary claim the marine biologist is trying to prove, marked by the indicator 'Consequently'.
2
Identify the premises and the logical gap.
Premises: The sponge cannot filter-feed (no pores) and cannot hunt (no zooplankton prey). Gap: Ruling out other food sources does not automatically prove bacteria are the actual food source, nor does it rule out other unknown methods of feeding.
Understanding the gap allows us to find evidence that either confirms the bacterial connection directly or rules out remaining alternative explanations.
3
Evaluate the options against the logical gap.
The isotopic analysis confirms a direct nutritional link, and the antibiotic observation proves the bacteria are necessary for survival. Both independently strengthen the argument.
Strengthening an argument requires finding new information that makes the main conclusion more plausible.

Key Concept

Strengthen - Ruling out alternatives and validating mechanisms in causal reasoning.
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