Aquatic Desert Animals

Paragraph 1：It may seem surprising, but desert animals have made few specific bodily adaptations to the desert environment. Rather, they manage to survive through proper timing of their biological activities, and this is best illustrated by semiaquatic and aquatic desert animals. 

 

Paragraph 2：The aquatic nature of amphibians makes them seem unlikely desert residents. Reproduction requires open water, where the female and male deposit the eggs and sperm, respectively, and fertilization occurs. Development of the fertilized eggs occurs in water, and the gilled and legless juveniles must swim and feed in water. It is only the adult that can survive on land, but the poorly developed lungs and water-permeable skin restrict them to moister habitats. Amphibians beat the odds, not with extremely adaptive structures or organic processes but with a life history in which their activity and reproduction occur during brief periods of favorable conditions. And no amphibian better illustrates this ability than the spadefoot toad of the southern United States deserts. 

 

 

1. 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. 

 

A. Amphibians have not been able to develop the structures or processes needed to survive in the desert. 

 

B. Desert amphibians survive not through physical adaptations or organic processes but by being active and reproducing during favorable conditions.

 

C. The life history of desert amphibians begins with reproduction followed by short periods of activity. 

 

D. Desert amphibians require favorable conditions in order to develop the kinds of physical adaptations needed to survive in the desert. 

 

 

 

 

 

Paragraph 3：During the drier winter season the adult spade foot remains dormant underground, sometimes nearly a meter deep. Nested below the surface, where the toad is protected from desiccating air and temperature extremes, the spadefoot is enveloped by un-shed skin that forms a cocoon of sorts. Water stored in tissue and in the bladder is slowly lost, but the spadefoot is able to lose some 50 percent of its water and survive. And so the toad waits, sometimes for more than two years, until heavy rains come with enough moisture to create temporary pools in which it can reproduce. 

 

 

 

2. According to paragraph 3, the spadefoot toad is able to survive the drier winter season for all of the following seasons EXCEPT: 

 

A. It remains inactive deep underground during the winter months. 

 

B. It is protected from harsh conditions by a layer of un-shed skin that surrounds its body. 

 

C. It is able to survive losing half of the water from its body. 

 

D. It warms itself during periods of less extreme temperatures.

 

 

 

 

 

Paragraph 4：Water will awaken spadefoot toads, but in some cases simply the thumping of raindrops on the surface is enough to arouse them from their torpor. Hastening to shallow, temporary pools, the spadefoots mate. The females lay several thousand eggs that are less than 2 millimeters in diameter. The fertilized eggs develop quickly, and in warm water the tadpoles can emerge from their eggs shells in less than two days. Tadpole development requires just one to three weeks, and if pool evaporation is outpacing development, metamorphosis (the series of physical changes occurring after hatching or birth) is accelerated, resulting in smaller spadefoots. The omnivorous tadpoles can resort to cannibalism, the larger eating the smaller, and predation by other species is also common. Mortality is high, and not infrequently the pool dries before even the largest tadpoles have fully metamorphosed into adults. Spadefoot tadpole can help prolong the life of their aquatic habitat, however. Before full metamorphosis they collect into squirming swarms that agitate the water and stir the mud, thereby creating a deeper depression that retains the water. After they are fully metamorphosed and leave their aquatic nursery, adult spadefoot toads feed on the insects flourishing in the moist post-rain environment before returning underground to wait out the next drought. 

 

 

3. Why do spadefoot tadpoles “agitate the water and stir the mud” of their aquatic habitat? 

 

A. To help reduce predation by other species 

 

B. To speed up metamorphosis 

 

C. To escape from their aquatic nursery once they have fully metamorphosed 

 

D. To deepen their pool of water so it dries up less quickly

 

 

 

4. Paragraph 4 suggests that which of the following affects the timing of when spadefoot tadpoles emerge from their shells? 

 

A. The number of spadefoot eggs in the water 

 

B. The number of eggs laid by the female 

 

C. The temperature of the surrounding water

 

D. The rate of their metamorphosis 

 

 

 

5. According to paragraph 4, the metamorphosis of spadefoot tadpoles is accelerated if 

 

A. the fertilized eggs hatch too soon 

 

B. water is warmer and more plentiful than average 

 

C. water is evaporating more quickly than development is occurring

 

D. the tadpoles are too small to avoid predation 

 

 

 

6. Paragraph 4 mentions all of the following as reasons for the high mortality rate among spadefoot toad tadpoles EXCEPT 

 

A. predation by adult spadefoots

 

B. cannibalism of small tadpoles by larger tadpoles 

 

C. predation by other species 

 

D. evaporation of pools before the tadpoles have fully developed into adults 

 

 

 

 

 

Paragraph 5：Even more surprising are the aquatic animals that find a way to survive in the desert. Temporary bodies of water, including flat-bottomed basins known as playas, can host strictly aquatic species, the most prominent of which are crustaceans such as fairy shrimp. 

 

 

 

7. In describing some species as “strictly” aquatic, the author means that these species 

 

A. exist in aquatic environments only

 

B. require specific kinds of aquatic environments 

 

C. spend part but not all of their lives in water 

 

D. normally require aquatic environments 

 

 

 

 

 

Paragraph 6：The fairy shrimp survive as cysts, actually shelled embryos, in the dry playas of the Mojave Desert. Here they may reside for years, possibly even several decades, dehydrated, inactive, and inconspicuous. Under the right conditions, rain will bring the fairy shrimp out of dormancy. Cooler, near-freezing temperatures promote hatching, for in the Mojave Desert heavy rains and more reliable playa flooding occur in winter. Timely hatching is also promoted by dilute, non-saline water that comes with initial playa flooding. With time the playa’s salts permeate the water, and further cyst hatching is inhibited as the lake dries. However, additional rains may dilute the salts, and hatching is renewed with the promise that the lake’s life will be prolonged. 

 

 

 

8. According to paragraph 6, why might fairy shrimp cysts in the Mojave Desert tend to hatch when temperatures are near freezing? 

 

A. Desert rain contains the most salts during the winter. 

 

B. The heaviest rains in that area generally occur during the coldest time of the year.

 

C. Cold weather prevents the playa’s salts from entering the water. 

 

D. Damaging playa floods are less likely to occur when temperatures are low. 

 

 

Paragraph 7：The cysts hatch promptly but often face a less-than-ideal environment. Nevertheless, complete development may take as little as ten days. With time, more and more predators arrive, including winged insects that arrive from afar. The fairy shrimps that survive readily reproduce, and the resulting cysts settle to the bottom and are left to survive the next drought. Thus, as long as water persists three weeks or so, the fairy shrimp has time to complete its life cycle. 

 

 

 

9. What can be inferred from paragraphs 6 and 7 about fairy shrimps of the Mojave Desert? 

 

A. They spend only a small part of their lives as adults.

 

B. Cysts hatch during several seasons of the year. 

 

C. Cysts that take more than ten days to develop are more likely to survive. 

 

D. Adults usually reproduce multiple times during their lives. 

 

 

 

10. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selected THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points. 

 

The presence of animals that are dependent on water in the desert environment may seem surprising but it does occur. 

 

 

 

Answer Choices: 

 

A. Semiaquatic and aquatic species survive in the desert by concentrating their activity and reproduction within brief periods when water is available. 

 

B. Adult spadefoots can survive years of drought by staying dormant underground, but as soon as heavy rains come they mate and tadpoles mature fast to reach adulthood before pools dry up. 

 

C. When pools begin drying up too quickly, tadpoles often survive by burying themselves in mud until they have become fully metamorphosed into adults and are capable of reproduction. 

 

D. Semiaquatic and aquatic species reproduce in underground pools of water that are protected from drying up. 

 

E. Aquatic fairy shrimp cannot survive without water as adults, but their cysts stay dormant until the right conditions give them a chance to hatch, mature, and reproduce. 

 

F. Fairy shrimp cysts must be able to stay dormant for longer periods than adult spadefoot toads stay dormant because the near-freezing temperatures the cysts require to survive occur very infrequently. 

 

 

 

 

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