#12 - On their way from their nest to a food source, ants of

[BMM2021]

Hi,

In trying to figure out how to avoid making the mistake I made on this question (choosing E instead of C) again, I'm running into a lack of understanding regarding how to parse the wording correctly in each answer choice.

I initially skipped over C fairly quickly, since the wording to me implies that (if they exist) the ants foraging for food in the Sahara at noon don't generally use pheromones as a means of navigation: "...generally do not use pheromones to guide themselves between food and their nest." I thought a statement like this was unfounded; just because the pheromones might evaporate doesn't mean ants living in the Sahara wouldn't persist in using them for navigation, generally. Perhaps the ants die out within a week due to a singular reliance on pheromone navigation; perhaps they're terrible at foraging in the Sahara for that reason. Either way, I don't see how the language of answer C implies that hypothetical ants foraging are necessarily successful in their foraging, and thus would require some other kind of navigational tool to be successful.

In turn, I chose E, although I recognized there isn't a whole lot of reason to argue that ants foraging in the Sahara without pheromones couldn't accidentally become more efficient in navigating (e.g. bumping into rocks gets them home sooner than pheromones would have, coincidentally). Nevertheless, E didn't seem to inappropriately deny ants in the Sahara the faulty use of pheromones like C did to me.

So, what about the wording of answer C allows us to assume that the hypothetical Saharan ants would be successful in foraging, and would thus need to rely on something other than pheromones to navigate?

[Adam Tyson]

The stimulus provides some very strong evidence, BMM2021, and that strong evidence provides some support for answer C. The stimulus tells us that "All pheromones evaporate without a trace almost immediately when temperatures rise above 45 degrees Celsius." That's a no-exceptions rule - not that they "might" evaporate as you said, but that they ALL evaporate with NO trace, so there is no way for an ant to use that pheromone to navigate.

From there it's an easy jump to say that if an ant forages only on a typical afternoon in the Sahara, pheromones won't help them find there way back to the next after they find food. They couldn't use pheromones, because they disappear without a trace in that heat! They would be forced to use some other method for navigation, or just find their way home by dumb luck. It's not a question of how successful they are; it's that they cannot use the pheromone method at all, even unsuccessfully, because the pheromones aren't there for them to use.

The problem with answer E is that we cannot know whether ants in that place and time are more or less efficient than at other times, because we cannot know if those ants rely on pheromones. Maybe ants that forage in the Sahara in the afternoon use magnetic fields to navigate, or visual cues, or sonar. Maybe they leave behind some substance other than pheromones that does not evaporate, and they follow the sight or smell or taste of that other thing. They could be just as efficient, even more efficient, in the afternoon than at other times.