Explanation
Correct answer: B.
Choice B is the best answer. The text describes a study examining the relationship between a species of parasitic tapeworm, A. brevis, and its host insect, the T. nylanderi ant. According to the text, researchers were surprised to find that the tapeworm extends the life of its ant host, rather than reducing it. The text goes on to state that the infected ants end up doing less work to sustain the colony and that as a result, the uninfected ants take on the infected ants’ share of labor in addition to caring for them in their infected state. The study’s researchers also observed that the uninfected ants have shorter lifespans than expected. If the infected ants, who are doing less work in the colony, have longer lifespans, it can be inferred that the less an ant works, the longer it will live. The opposite of this statement can also be inferred: the more an ant works, the shorter its life. So, since the workload within the colony is being redistributed so that the infected ants work less while the uninfected ants work more (as they take on the neglected duties of the infected ants and also care for those ants), then it can be inferred that the lifespans of the uninfected ants are shortened because the need to compensate for reduced contributions within the colony while also caring for infected workers is burdensome to the uninfected workers.
Why the other choices are wrong
Choice A
Choice A is incorrect because the text does not indicate how A. brevis is transmitted to the ants or assert that uninfected ants are more likely to be directly exposed to A. brevis while caring for infected ants.
Choice C
Choice C is incorrect because the text makes no mention of the relative abilities of infected and uninfected ants to escape predators: in fact, predators are not mentioned in the text at all.
Choice D
Choice D is incorrect because the text does not supply any information about the average lifespans of the ants in colonies without parasitic activity; the text only indicates factors that lengthen and shorten the lifespans of ants in parasitized colonies.
Student discussion
shahdia2911 0 likes
Because the worker ants take over the physical labor of the infected ants, they seem to have shorter lifespans. When the uninfected workers take over all the work and get less food out of it, it is burdensome.