Scientist: Some colonies of bacteria

Answer choices

1. A

   Correct47% picked this

   Bacteria colonies that do not produce phenazines form wrinkled surfaces, thus increasing the number of bacteria that are in direct

   Why this is right

   This answer is using the classic "No Cause, No Effect" type structure, but it's pretty confusing to process. The "problem" that phenazines are supposedly solving is, "How do we get nutrients from the outside of the colony to the inside? The bacteria in the inside of the colony are trapped. They're surrounded by other bacteria in the colony. They can't eat their own colony. So we have to pass them food from the exterior". If the bacteria has a wrinkled surface, then more of the colony is in direct contact with the surrounding environment. We don't have bacteria that are trapped. Most / all of them have some direct contact with the surrounding environment, so they can get their own food. Thus, since they don't have the problem of "how do we get food to the bacteria that has no direct contact with the environment", they don't have the evolutionary "solution" of phenazine pipelines.

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

   47%
2. B

   No Impact11% picked this

   The rate at which a bacteria colony produces phenazines is determined by the number of foreign bacteria in the

   This doesn't give us any reason to think these things work as pipelines to get food from the exterior of the colony to the trapped bacteria on the inside. Instead, this answer reinforces the other function of phenazines, defending against foreign bacteria. This answer is showing how phenazine production is proportional to "need to defend against foreign bacteria". Since the growth of phenazine is directly tied to this other function, if anything this answer would weaken the notion that phenazine is also integral as a food pipeline (this answer suggests that if there were no foreign bacteria in the surrounding environment, there might not even be phenazines).

   11%
3. C

   Weakens, if anything10% picked this

   When bacteria colonies that do not produce phenazines are buried in nutrient-rich soil, they grow as quickly as

   If phenazines were nutrient-pipelines that help feed the starving centers of bacteria colonies, then we would expect colonies with phenazines to be more successful than colonies without. But according to this answer, if you throw both types of bacteria into nutrient-filled soil, they do about equally well.

   10%
4. D

   No Impact24% picked this

   Bacteria colonies that produce phenazines are better able to fend off other bacteria than are bacteria colonies that

   This is similar to (B). It's related to the known function of phenazines -- fending off bacteria. This answer provides nothing that helps support the idea that phenazines also perform the function of being a nutrient pipeline to the city-center of the bacteria colony.

   24%
5. E

   Unclear Impact8% picked this

   Within bacteria colonies that produce phenazines, interior bacteria are more likely to die than are

   On one hand, maybe we could say, "See? The hypothesis is right. These bacteria that have phenazines have a problem with interior bacteria starving because they're trapped from nutrients!" But on the other hand, we could say, "Hmmm, looks like the hypothesis is wrong. Supposedly the phenazine should be piping nutrients to these interior bacteria, but it looks like they're not, since those interior bacteria are dying." I think LSAC intended this more as a Weaken idea.

   8%