Sociality in Animals

Paragraph 1: Social insects represent the high point of invertebrate evolution. Some species live in communities of millions, coordinating their building and foraging, their reproduction, and their offspring care. Yet sociality is found in only a few species of insects, and is rare among vertebrates as well: wildebeest (large antelope) and lions are the exception rather than the rule. Nearly all fish, amphibians, reptiles, birds, and mammals are solitary, except when courting and mating. Birds and mammals usually rear their young, but year-round family groups are almost unknown, though they are intensely studied where they do exist. The same is true for insects.

 

 

 

1. According to paragraph 1, which of the following is true of sociality among animal species?

 

O Sociality is much more common among invertebrates than among vertebrates.

 

O Very few animals are considered social because most spend the majority of their lives alone.

 

O An animal group must contain more than one family unit for the species to be considered social.

 

O All animals that rear their young are considered to be social.

 

 

 

 

 

Paragraph 2: We know, or think we know, that social groups are good. Wolves are better predators when they hunt in packs, and pigeons escape from falcons far more often when feeding in flocks. Group building projects—the dams beavers build to block a body of water that provides them with relative safety from predators and the lodges they build for shelter, for instance—can provide a high level of protection and comfort. Why, then, are social species so very rare? In fact, living socially presents inevitable problems that transcend habitat needs so that only when these costs are offset by corresponding benefits is group living a plus.

 

 

 

2. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

 

O Group living allows some animals to transcend problems of habitat.

 

O Group living is only advantageous when benefits ouTweigh inevitable problems.

 

O Problems resulting from living socially extend beyond the habitat.

 

O It is difficult to determine whether the benefits of social living offset its costs.

 

 

 

 

 

Paragraph 3: The most obvious cost is competition. All the members of a species share the same habitat; when they live together, they are trying to eat the same food and occupy the same nesting sites. In general, there is far less competition away from a group, and selection should favor any individual who (all things being equal) sets off on its own, leaving the members of its group behind to compete among themselves for limited resources. Another difficulty is that concentrations of individuals facilitate disease and parasite transmission. On the whole, social animals carry more parasites and species-specific diseases than do solitary animals. Parasites and diseases diminish the strength and limit the growth of animals, and among highly social creatures, epidemics can devastate whole populations. Distemper (a viral disease) has been known to wipe out entire colonies of seals, for instance. So the penalty of social life is potentially huge.

 

 

 

3. What does paragraph 3 say about the relationship beTween natural selection and animals that live apart from other members of their species?

 

O Natural selection does not favor living apart because individuals are unable to obtain resources equal to those of group members.

 

O Natural selection does not favor living apart because of the intense competition for resources among individuals apart from a group.

 

O Natural selection favors living apart because individuals are unlikely to attract the attention of predators.

 

O Natural selection favors living apart because group living increases competition for limited resources of food and nesting sites.

 

 

4. In paragraph 3, why does the author mention distemper and its effect on seals?

 

O To explain why sociality is now relatively rare in seals

 

O To prove that parasites prevent animals from growing healthy and strong

 

O To show how easily social animals transmit potentially deadly diseases

 

O To provide an example of a species-specific disease that affects solitary animals

 

 

 

 

 

Paragraph 4: But in some instances, the payoffs can be even greater. Two have already been mentioned: cooperative hunting and defensive groups. Social hunting is likely to evolve where prey is too large to be taken by individuals operating alone. To capture wildebeest some members of a group of lions follow their prey and herd them toward others lying in ambush. In other species, individuals forage or hunt simultaneously and share the food. Vampire bats that have had a bad day, for instance, are fed by more successful members of the community, but they are expected to return the favor in the future. Cooperation can even involve sharing information about the location of food. Some colonial birds, such as bank swallows, use the departure direction of a successful forager (food hunter) to locate concentrations of prey. Information transfer can be unintentional though some species make use of special assembly calls or behavior.

 

 

5. According to paragraph 4, how do lions increase their chances of successfully hunting wildebeest?

 

O They work together as a team to chase and capture the animals.

 

O They wait until groups of the animals come close to their hiding place.

 

O They follow and catch the animals that are operating alone.

 

O They focus on the smallest members of the species.

 

 

 

6. Which of the following can be inferred from paragraph 4 about how bank swallows find food cooperatively?

 

O They give special favors to members of their community that have been successful foragers.

 

O They use special calls and signals to indicate to other swallows where food is located.

 

O They observe the direction a successful forager took to locate prey.

 

O They locate concentrations of prey by setting off in different directions.

 

 

 

 

 

Paragraph 5: Cooperation in group defense, such as we see in circles of musk oxen or elephants, is quite rare among vertebrates but is prevalent among the social insects. The strategy of employing many eyes to watch for danger, on the other hand, is widespread in birds and mammals. A herd of gazelles (small antelope) is far more likely to spot a lurking lion or a concealed cheetah than is a lone individual, and at a greater distance. In fact, a group enters into a kind of time-sharing arrangement in which individual antelope alternate biting off a mouthful of grass with a period of erect and watchful chewing. A larger group can afford more bites per individual per minute, there being more eyes to scan for danger. For a small antelope living in a forest where visibility is limited, however, remaining hidden is probably a better bet than assembling into noisy herds.

 

 

7. According to paragraph 5, how does cooperation help gazelles avoid predation?

 

O The herd forms a defensive circle around the weakest members of the group.

 

O Because they share food, all of the animals are well nourished and ready to run.

 

O The herd makes a lot of noise, which scares off predators.

 

O Some animals watch for danger while others concentrate on feeding.

 

 

 

 

 

Paragraph 6: Among the millions of species of insects, only a few thousand are social. Those rarities are generally confined to termites and Hymenoptera. All termites are social: their diet (cellulose) requires that each generation feed a special kind of bacteria or fungi to the next generation to aid in its digestion. Of the numerous hymenopterans, some are social—including all ants and a few bees and wasps—but many are solitary.

 

 

 

8. Which of the following can be inferred from paragraph 6 about termites?

 

O They are the only insect species whose members are all social.

 

O They have smaller communities than hymenopterans.

 

O They are more independent than hymenopterans.

 

O They have to live together to pass on digestive bacteria to their young.

 

 

 

 

 

Paragraph 2: We know, or think we know, that social groups are good. ■ Wolves are better predators when they hunt in packs, and pigeons escape from falcons far more often when feeding in flocks. ■ Group building projects—the dams beavers build to block a body of water that provides them with relative safety from predators and the lodges they build for shelter, for instance—can provide a high level of protection and comfort. ■ Why, then, are social species so very rare? ■ In fact, living socially presents inevitable problems that transcend habitat needs so that only when these costs are offset by corresponding benefits is group living a plus.

 

 

 

9. Look at the four squares [■] that indicate where the following sentence can be added to the passage.

 

The engineering of structures of such size and complexity is unknown among solitary animals.

 

Where would the sentence best fit?

 

 

 

 

 

10. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. Drag your choices to the spaces where they belong. To review the passage, click on View Text.

 

Some animal species demonstrate sociability, but solitary behaviors are far more typical among animals.

 

 

 

Answer Choices

 

O Because birds and mammals engage in courting, mating, and establishing year-round family groups to rear young, they are most likely to be social species.

 

O Some social animals obtain food through cooperation and share food and information about food sources with each other.

 

O Social animals help each other watch for danger more effectively, and some species work together to combat predators.

 

O Living in communities presents disadvantages, such as the competition for resources and the easy transmission of diseases.

 

O Some entire species of social animals have become extinct because of disease epidemics.

 

O Although some species of ants, bees, and wasps are famous for their sociality, most social insects are not hymenopterans.

 

 

 

 

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