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GMAT – Section 3: Test 5

Justice June 5, 2015

Verbal (Questions 90 – 92)

INSTRUCTIONS:

Use the following to answer questions 90 through 92.

The naked mole rat, also known as the sand puppy, is a unique member of the animal kingdom. Born with no hair and growing only a few tiny translucent hair fibers over the company of a lifetime, naked mole rats spend their entire lives underground. During this subterranean existence naked mole rats are part of a large eusocial colony. This complex social structure dictates that one breeding female and, at most, two breeding males lead the colony, while all other members are relegated to worker roles. What sets the naked mole rat apart is that it is the only known mammalian species (of the genus Heterocephalus) that operates a eusocial colony.
Eusocial populations are those where a specialized caste carries out reproduction in a colony of otherwise non-reproductive animals. Eusociality in the animal kingdom is most common among insect populations of the order Hymenoptera, such as ants, bees, wasps, and termites. Eusocial behavior also occurs in certain arthropod populations, but naked mole rats currently represent the only clear-cut example of a eusocial mammal. In all eusocial colonies the reproductive caste is distinct from the other members of the colony as they are the only animals that are reproductively viable. In both insect colonies and naked mole rat colonies the dominant female and any female that eventually succeeds her usually arise via a mechanism W.D. Hamilton termed ‘supersisters,’ where heirs to the reproductive throne are usually more genetically similar to one another and the queen than to any other offspring they themselves might produce. In naked mole rat colonies, much like insect colonies, the reproductive female is usually succeeded upon death or infertility by a supersister who arises from among the worker caste. This form of kin selection, while successful, has confounded scientists who wonder how eusocial colonies thrive in the face of Darwinian evolution. Furthermore, scientists have been amazed to find that the sterility that exists among other females in the colony is only temporary and not genetic. After the battle that often ensues between two females vying for the queen’s throne, the winner is then able to reproduce offspring, whereas before they were physiologically unable to. When a naked mole rat female produces offspring, she usually does so in numbers that exceeds the number of mammary glands she has. Naked mole rats are able to manage this feat, whereby there are more offspring than there are feeding sites on the mother’s underside, because of their truly eusocial nature, which allows the mother to devote the vast majority of her time to producing, feeding, and caring for her young. Other members of the colony participate in rearing and feeding offspring, though only in an ancillary role. These two traits in particular distinguish Heterocephalus Glaber from other members of the class mammalia who exhibit elements of eusociality, such as wild dogs, where reproduction is conducted by alpha males and females that dissuade other colony members from reproducing through aggressive behavior.

 

10th Grade ELA – Pre-test Assessment 2