Logical Reasoning

PT107 · S4 · Q20 Amphibian populations are declining

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Amphibian populations are declining in numbers worldwide.

Conclusion (Thus)

The primary cause of the declining amphibian population is the depletion of the ozone layer.

Evidence

The ozone layer has been continuously depleted throughout the last 50 years. Ozone blocks UV-B, which can damage genes. Amphibians lack features to shield them from UV-B, so they are particularly vulnerable (their eggs, too!)

Evaluate

Since this argument is concluding that "ozone decline" is the primary cause of "declining amphibian population", we have two ways to strengthen it:

- rule out the idea that something else is the primary cause of declining amphibians (they're not declining primarily because of pollution or global warming)

- boost the plausibility of the author's story that ozone is hurting amphibian populations (the holes in the ozone layer are where the amphibians live / amphibians come out during the day when they can hit by UV / the damage to their genes would be enough to cause a decline in their numbers)

Goal

Get rid of the four answers that strengthen. Pick what's left. It's common on EXCEPT questions for one of those four answers to work a different way than the others, so we might even anticipate that 3 of them will boost plausibility (the more common way to Strengthen) and 1 of them will rule out an alternate cause.

20.

Each of the following, if true, would strengthen the argument EXCEPT:

  1. Correct

    Of the various types of

    Why this is right

    Do we care if UV-B is the only type that damages genes? Would it weaken the argument if other types of radiation blocked by atmospheric ozone also damaged genes? Would that hurt the author's conclusion that the depleting ozone layer is the primary cause of what's killing amphibians? No, that would only strengthen it. Depletion of the ozone layer is scarier if the ozone usually blocks multiple types of gene-damaging radiation that if it only blocks one type of gene-damaging radiation. The more types of gene-damaging radiation that get through, the worse a depleted ozone layer is for amphibians, which just helps the author's conclusion. So, if anything, this answer weakens (not that it needs to in order to be correct).

    Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.

    52% picked this

  2. Amphibian populations are declining far

    Boosts Plausibility

    This adds plausibility to the author's story by providing more data that declining population is tied to vulnerability to UV-B. The animals whose eggs are more vulnerable to UV-B are declining more, and since depletion of the ozone layer allows more UV-B to come through, it looks like depletion of the ozone layer could be hurting those animals.

    3% picked this

  3. Atmospheric ozone has been significantly

    Boosts Plausibility

    This helps the plausibility of the hypothesis that "ozone depletion" is causing "amphibian population decline" by putting the Suspect at the Scene of the Crime. In order for ozone depletion to be the causal agent that's affecting amphibians, we need to put them in the same room together. If amphibians lived in areas of Earth where the ozone layer weren't depleted, then the author's hypothesis would be pretty far-fetched. A necessary assumption the author's hypothesis makes is that "at least some amphibians are getting more UV-B because of ozone depletion than they otherwise would", which assumes that amphibians live somewhere that there is ozone depletion. This answer gives us a strong version of that necessary assumption, saying, "Yes, everywhere that amphibians are declining, ozone depletion is present." (Cause and Effect appear together)

    2% picked this

  4. The natural habitat of amphibians

    Rules Out Alternate Explanation

    This strengthen by ruling out an alternate possibility for the primary cause of declining amphibian populations -- it's not because their habitat is disappearing.

    36% picked this

  5. Amphibian populations have declined continuously

    Boosts Plausibility

    This strengthens the correlation between the putative cause and effect. We know that ozone has been depleting continuously for the last 50 years. If at the same time amphibian populations have been declining continuously, it establishes a strong correlation between what the author thinks is the Cause (ozone depletion) and what the author thinks is the Effect (declining amphibians). Anyone claiming that "X is causing Y" is corroborated by a correlation showing that "As X has increased, so too has Y increased".

    7% picked this

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