Logical Reasoning

PT140 · S3 · Q16 Zoologist: In the Lake Champlain

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Zoologist: In the Lake Champlain area, as the North American snowshoe hare population grows, so do the populations of its predators.

Curious Fact / Evidence

Why do we observe snowshoe hares everywhere following this same cycle?

more hares -> more predators -> hares retreat to less food -> hare population drops -> predators decline -> hares rebound

Explanation / Conclusion

Sunspot activity is probably also a causal factor in the hare cycle.

Evidence

Hare population cycles are well correlated with the regular cycle of sunspot activity, AND the local predator-prey dynamic alone can't explain why hare populations everywhere cycle simultaneously.

Evaluate

When we're trying to strengthen an Explain Curious Fact style argument, we primarily expect answers to 1) increase the plausibility of the author's causal storyline but we also see answers 2) rule out an alternate causal storyline for the curious fact

Goal

Get rid of four answers that either 1) make it more plausible that sunspot activity from the sun influences this population cycle of the snowshoe hare

2) undermines some alternate explanation for the snowshoe hare's population cycle.

16.

Each of the following, if true, supports the zoologist's reasoning except:

  1. Reproduction in predator populations increases

    Strengthens

    This helps increase the plausibility that sunspots are a causal factor in the population cycle, because sunspots are affecting how much the predators reproduce. Sunspots could be triggering the uptick in predator populations, which sends the hares into more heavily forested areas, which leads to fewer hares, which leads to fewer predators, etc.

    9% picked this

  2. Correct

    Local weather patterns that can

    Why this is right

    When we say that "X can occur in the presence or absence of Y", it suggests that Y doesn't have much to do with X. So this is essentially saying, "Local weather patterns that affect population changes don't have much to do with sunspot activity". It almost starts to weaken by introducing another causal explanation (rather than strengthen by ruling one out). This answer makes us start to think that maybe the population patterns of the hare and its predators aren't related to sunspots, but rather are connected to these local weather patterns.

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

    72% picked this

  3. Brighter light during sunspot activity

    Strengthens

    This helps increase the plausibility that sunspots are a causal factor in the population cycle, by providing another causal mechanism for how sunspot activity could affect hares or their predators. In this case, sunspots improve the ability of predators to catch hares. Knowing that sunspot activity has some causal influence on something that would affect the population levels of hares and/or their predators, adds some plausibility to the author's claim that "sunspot activity is a causal factor in the hare/predator population cycle".

    7% picked this

  4. The variation from cycle to

    Strengthens

    This adds plausibility by deepening the correlation we had in the evidence. Now we know that not only do hare cycles match sunspot cycles in timing, they also match in magnitude — bigger sunspot peaks correspond to bigger hare-population peaks. That's a much tighter correlation, which strengthens the case for a causal connection.

    5% picked this

  5. Sunspot activity is correlated with

    Strengthens

    This helps increase the plausibility that sunspots are a causal factor in the population cycle, by providing another causal mechanism for how sunspot activity could affect hares or their predators. In this case, sunspots affect the nutritional value of the hares' food. Knowing that sunspot activity has some causal influence on something that would affect the population levels of hares and/or their predators, adds some plausibility to the author's claim that "sunspot activity is a causal factor in the hare/predator population cycle".

    7% picked this

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