Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial...
GMAT Reading Comprehension : (RC) Questions
Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees, whereby individuals cooperate, sometimes even sacrificing their own opportunities to survive and reproduce, for the good of others. However, such a vertebrate society may exist among underground colonies of the highly social rodent Heterocephalus glaber, the naked mole rat.
A naked mole rat colony, like a beehive, wasp's nest, or termite mound, is ruled by its queen, or reproducing female. Other adult female mole rats neither ovulate nor breed. The queen is the largest member of the colony, and she maintains her breeding status through a mixture of behavioral and, presumably, chemical control. Queens have been long-lived in captivity, and when they die or are removed from a colony one sees violent fighting for breeding status among the larger remaining females, leading to a takeover by a new queen.
Eusocial insect societies have rigid caste systems, each insect's role being defined by its behavior, body shape, and physiology. In naked mole rat societies, on the other hand, differences in behavior are related primarily to reproductive status (reproduction being limited to the queen and a few males), body size, and perhaps age. Smaller non-breeding members, both male and female, seem to participate primarily in gathering food, transporting nest material, and tunneling. Larger nonbreeders are active in defending the colony and perhaps in removing dirt from the tunnels. Jarvis' work has suggested that differences in growth rates may influence the length of time that an individual performs a task, regardless of its age.
Cooperative breeding has evolved many times in vertebrates, but unlike naked mole rats, most cooperatively breeding vertebrates (except the wild dog, Lycaon pictus) are dominated by a pair of breeders rather than by a single breeding female. The division of labor within social groups is less pronounced among other vertebrates than among naked mole rats, colony size is much smaller, and mating by subordinate females may not be totally suppressed, whereas in naked mole rat colonies subordinate females are not sexually active, and many never breed.
Which of the following most accurately states the main idea of the passage?
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| Until recently, scientists did not know of a close vertebrate analogue to the extreme form of altruism observed in eusocial insects like ants and bees, whereby individuals cooperate, sometimes even sacrificing their own opportunities to survive and reproduce, for the good of others. | What it says: Scientists couldn't find animals with backbones that acted as selflessly as certain insects do - where individuals give up their own survival/reproduction to help the group. What it does: Sets up a scientific problem/gap in knowledge that the passage will address Source/Type: Factual statement about state of scientific knowledge Connection to Previous Sentences: This is our starting point - establishes the central puzzle Visualization: Think of a bee dying to protect its hive - scientists knew insects did this extreme self-sacrifice, but couldn't find mammals, birds, fish, etc. that did the same Reading Strategy Insight: This "Until recently" signals that we're about to learn about a discovery that fills this gap |
| However, such a vertebrate society may exist among underground colonies of the highly social rodent Heterocephalus glaber, the naked mole rat. | What it says: Scientists may have found the missing example: naked mole rats might show this extreme cooperation What it does: Introduces the main subject and potential answer to the problem posed in sentence 1 Source/Type: Scientific hypothesis/discovery Connection to Previous Sentences: This directly answers sentence 1's gap - the "However" signals we're getting the solution to the "scientists did not know" problem Visualization: Underground tunnels with small, hairless rodents living in large groups, possibly acting like the self-sacrificing insects from sentence 1 Reading Strategy Insight: Feel confident here - this is solving the puzzle, not adding complexity |
- The passage explicitly states that "Cooperative breeding has evolved many times in vertebrates" and mentions wild dogs as another example
- This choice ignores the extensive discussion of other cooperative vertebrates in the final paragraph
- The word "only" makes this an extreme overstatement that contradicts the passage
- Did the passage focus so much on naked mole rats that they seem like the only cooperative vertebrates?
→ Re-read the final paragraph which explicitly discusses "many" other cooperative vertebrates - Does "unique" mean "only"?
→ The passage shows naked mole rats are unique in being closest to insects, not unique in being cooperative
- This directly answers the scientific puzzle posed in the opening sentence about finding vertebrate analogues to eusocial insect behavior
- The word "may" appropriately reflects the tentative language used throughout the passage ("may exist," "seem to," "perhaps")
- It captures the main comparative structure of the passage without overstating the conclusions
- This encompasses the entire argumentative arc from problem identification through evidence to tentative conclusion
- This focuses only on mating/reproductive behavior rather than the broader social organization that is the passage's main concern
- The passage mentions that wild dogs (Lycaon pictus) have similar single-female dominance, so mole rats aren't completely unique in mating structure
- The main point is about social cooperation and altruism, not specifically about mating habits
- Isn't the queen-dominated reproduction system the most important feature discussed?
→ It's one important feature, but the passage uses it as evidence for the larger point about resembling insect societies - Does the mention of wild dogs invalidate this choice?
→ Yes, the passage explicitly states wild dogs are an exception, meaning mole rats aren't unique in this way
- The passage actually emphasizes differences in how labor is divided: insects use "rigid caste systems" while naked mole rats use size, reproductive status, and age
- The author deliberately contrasts the basis for division of labor between the two groups
- This choice misses the key distinction the author makes between different organizational principles
- Don't both groups have specialized roles for different individuals?
→ Yes, but the passage emphasizes that the basis for these roles differs significantly between groups - Isn't having any division of labor the important similarity?
→ The passage suggests the basis for division matters as much as its existence in determining how closely societies resemble each other