A stingray without parasites is

Answer choices

1. A

   Correct68% picked this

   During part of their life cycles, the parasites of stingrays require as hosts shrimp or oysters, which

   Why this is right

   How is a lack of parasites in stingrays an indicator of a stressed ecosystem? Well, shrimp and oysters are indicators of a stressed ecosystem, since they are environmentally vulnerable. And the parasites that show up in stingrays have always lived previously in shrimp or oysters. So if parasites stop showing up in stingrays, it suggests that there weren't any shrimp or oysters around to get the parasites through that part of their life cycle. And if there aren't shrimp or oysters around, then it suggests that some environmental stressor has depleted populations of environmentally vulnerable organisms. Quite a reach, huh? No one said these correct answers have to be super convincing -- just "most helpful" out of the available options.

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

   68%
2. B

   Unrelated to Goal2% picked this

   A stingray is a free-ranging predator that feeds on smaller organisms but has

   This doesn't give us a way to explain why it's a bad sign for an ecosystem if stingrays don't have parasites.

   2%
3. C

   Explains Background5% picked this

   A parasite drains part of the vitality of its host by drawing nourishment

   This answer offers a reason why a stingray without parasites would be healthier than a stingray with parasites. That part of the paradox was already pretty self-justifying, from common sense. This answer isn't doing anything to tackle the more surprising claim, which doesn't have a common sense explanation -- why is it a bad sign for an ecosystem if its stingrays don't have parasites?

   5%
4. D

   Unrelated to Goal / Too Weak16% picked this

   An ecosystem can be considered stressed if only a few species of very simple organisms

   This doesn't give us a way to explain why it's a bad sign for an ecosystem if stingrays don't have parasites. It's also almost never the case that the correct answer to Strengthen, Weaken, or Paradox would be as weak as "X can be considered Y" (or as weak as some, sometimes, may, might, not always)

   16%
5. E

   Unrelated to Goal9% picked this

   Since the life of parasites depends on that of their host, they need to live without killing their host or else not reproduce and

   This doesn't give us a way to explain why it's a bad sign for an ecosystem if stingrays don't have parasites. If it's doing anything, it's explaining why parasites aren't lethal for stingrays.

   9%