Two Kinds of Lizards

 

Paragraph 1：Lizards can be divided into two types according to the way they look for food: sit-and-wait foragers and active foragers. Sit-and-wait lizards normally remain in one spot from which they can survey a broad area. These motionless lizards detect the movement of an insect visually and capture it with a quick run from their observation site. Sit-and-wait lizards may be most successful in detecting and capturing relatively large insects like beetles and grasshoppers. Active foragers, on the other hand, spend most of their time on the ground surface, moving steadily and poking their heads under fallen leaves and into crevices in the ground. These lizards apparently rely largely on chemical cues to detect insects, and they probably seek out local concentrations of prey such as termites. Active foragers appear to eat more insects than do lizards that are sit-and-wait predators. Thus, the different foraging behaviors of lizards lead to differences in their diets, even when the two kinds of lizards occur in the same habitat. 

 

 

 

 

1. According to paragraph 1, sit-and-wait foragers and active foragers are different in all of the following EXCEPT 

 

O the methods that they primarily use to detect insects 

 

O the number of insects they typically eat 

 

O the habitats in which they can be found

 

O the amount of time they spend moving 

 

 

 

2. According to paragraph 1, compared to the insects typically consumed by sit-and-wait lizards, insects typically consumed by active lizards 

 

O move more quickly 

 

O are generally found in smaller groups 

 

O are often hidden from view

 

O spend more time on the surface of the ground 

 

 

 

 

 

Paragraph 2：The different foraging modes also have different consequences for lizards regarding their exposure to predators. A lizard that spends 99 percent of its time resting motionless is relatively inconspicuous, whereas a lizard that spends most of its time moving is easily seen. Sit-and-wait lizards are probably most likely to be discovered and captured by predators that are active searchers, whereas widely foraging lizards are likely to be caught by sit-and-wait predators. Because of this difference, foraging modes may alternate at successive levels in the food chain: insects that move about may be captured by lizards that are sit-and-wait foragers, and those lizards may be eaten by active predators, whereas insects that are sedentary are more likely to be discovered by lizards that are active foragers, and those lizards may be caught by sit-and-wait predators. 

 

 

 

3. In paragraph 2, why does the author contrast the visibility of lizards that remain motionless most of the time with the visibility of lizards that move most of the time？ 

 

O To show that it is possible for lizards to alternate their foraging modes at successive levels in the food chain 

 

O To suggest that sit-and-wait lizards are more likely than active lizards to be attacked by predators 

 

O To explain why sit-and-wait lizards are more successful than active lizards at preying on insects 

 

O To explain how a lizard’s foraging strategy affects the type of predator likely to attack it

 

 

 

 

 

Paragraph 3：The body forms of sit-and-wait foragers may reflect selective pressures different from those that act on active foragers. Sit-and-wait lizards are often stout bodied, short tailed, and colored to match their background. Many of these species have patterns of different-colored blotches that probably obscure the outlines of the lizard’s body as it rests motionless on a rock or a tree trunk. Active foragers are usually slim and elongated with long tails, and they often have patterns of stripes that may produce optical illusions as they move. However, one predator-avoidance mechanism, the ability to break off their tails when they are seized by predators, does not differ among lizards with different foraging modes.  

 

 

 

 

 

4. Paragraph 3 supports which of the following ideas about active-forager lizards？ 

 

O They are less likely to break off their tails when seized by predators than sit-and-wait lizards are. 

 

O They tend to vary widely in their individual colors. 

 

O They lack well-developed mechanisms for avoiding predators. 

 

O They may be easier to identify when they are not moving than when they are moving.

 

 

 

 

 

Paragraph 4：What physiological characteristics are necessary to support different foraging modes? The energy requirements of a quick motion that lasts for only a second or two are quite different from those of locomotion that is sustained nearly continuously for several hours. Sit-and-wait lizards and active foragers differ in their relative emphasis on the two ways that most animals use adenosine triphosphate (ATP), a molecule that transports energy within cells for activity, and in how long that activity can be sustained. Sit-and-wait lizards move in brief spurts, and they rely largely on anaerobic metabolism to sustain their movements, namely the kind of metabolism that does not use oxygen. Anaerobic metabolism uses glycogen stored in the muscles and produces lactic acid as its end product. It is a way to synthesize ATP quickly (because the glycogen is already in the muscles), but it is not good for sustained activity because the glycogen is quickly exhausted and lactic acid inhibits cellular metabolism. Lizards that rely on anaerobic metabolism can make brief sprints but become exhausted when they are forced to run continuously. In contrast, aerobic metabolism uses glucose that is carried to the muscles by the circulatory system, and it produces carbon dioxide and water as end products. Aerobic exercise can continue for long periods because the circulatory system brings more glucose and carries carbon dioxide away. As a result, active foragers can sustain activity for long periods without exhaustion. Active species of lizards have larger hearts and more red blood cells in their blood than do sit-and-wait species. As a result, each beat of the heart pumps more blood, and that blood carries more oxygen to the tissues of an active species than a sit-and-wait species. 

 

 

 

5. According to paragraph 4, compared with active lizards, the movements of sit-and-wait lizards are 

 

O more sudden

 

O more sustained 

 

O more predictable 

 

O more frequent 

 

 

 

6. According to paragraph 4, all of the following are true about anaerobic metabolism in lizards EXCEPT: 

 

O It uses the glycogen in the muscles of lizards. 

 

O It produces lactic acid that interferes with metabolism within the cells of lizards. 

 

O It allows lizards to maintain their foraging activity over a long period of time. 

 

O It allows lizards to run fast for short periods of time. 

 

 

 

7. Which of  the following can be inferred from paragraph 4 about sit-and-wait lizards？ 

 

O They have less glycogen than active-forager lizards. 

 

O They have highly variable heart rates. 

 

O They have metabolic systems that do not depend on the efficient removal of carbon dioxide.

 

O They synthesize adenosine triphosphate continuously. 

 

 

 

8. According to paragraph 4, how are active-foraging lizards and sit-and-wait lizards different from each other？ 

 

O Sit-and-wait lizards tend to have more red blood cells in their blood than active-foraging lizards do. 

 

O Active-foraging lizards’ blood carries less oxygen to the tissues than sit-and-wait foraging lizards’ blood does. 

 

O Sit-and-wait lizards carry out cellular metabolism more efficiently than active-foraging lizards do. 

 

O Active-foraging lizards tend to have larger hearts than sit-and-wait lizards do.

 

 

 

 

 

Paragraph 3：The body forms of sit-and-wait foragers may reflect selective pressures different from those that act on active foragers. Sit-and-wait lizards are often stout bodied, short tailed, and colored to match their background. ■Many of these species have patterns of different-colored blotches that probably obscure the outlines of the lizard’s body as it rests motionless on a rock or a tree trunk. ■Active foragers are usually slim and elongated with long tails, and they often have patterns of stripes that may produce optical illusions as they move. ■However, one predator-avoidance mechanism, the ability to break off their tails when they are seized by predators, does not differ among lizards with different foraging modes.■

 

 

 

9. Look at the four squares that indicate where the following sentence could be added to the passage. 

 

Such visual effects make it harder for predators to catch these moving targets. 

 

Where would the sentence best fit? Click on a square to add the sentence to the passage. 

 

 

 

 

 

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. Drag your choices to the spaces where they belong. To review the passage, click on View Text. 

 

 

 

Answer Choices 

 

O Sit-and-wait lizards use brief spurts of energy to forage, while the movements of active lizards are more sustained.

 

O Lizards that are active foragers are able to detect insects even when those insects are stationary, but sit-and-wait lizards are able to detect only moving insects. 

 

O Sit-and-wait lizards tend to have predators that are active, while active lizards tend to have sit-and-wait predators.

 

O Sit-and-wait lizards have less need for bodies that match their environment than active lizards do because of the ease with which they can break off their tails to escape from predators. 

 

O The body forms and metabolic functions of the two types of lizards differ in ways that support the requirements of their different foraging behaviors.

 

O Sit-and-wait lizards derive energy for movement from anaerobic metabolism alone, while active lizards rely almost equally on aerobic and anaerobic metabolisms.  

 

 

 

 

 

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