How Animals in Rain Forests Make Themselves Heard

Paragraph 1：Scientists have discovered that animals are experts at exploiting weather conditions and the physical conditions of their environments so that they are heard or not heard, and seen or not seen. The species living in rain forests must engineer their calls to accommodate all of the obstacles, such as leaf cover, that can deflect and degrade the sounds intended for a potential receiver. Over, short, loud bursts of sound tend to be more effective than longer calls at cutting through the dense foliage. 

 

 

Paragraph 2：There is no natural environment on Earth noisier than a virgin rain forest. In the Peruvian rain forest, every species has developed clever or remarkably sophisticated strategies to ensure that its voice is heard. The noise creates a real challenge for the smaller residents, such as male tree crickets, which need to get the attention of females, often from a relatively long distance. Some species of crickets maximize the volume of their calls by chewing a hole in the middle of a leaf to create a sound baffle, similar to a stereo speaker. The leaf functions as a speaker cabinet, with the cricket in the center acting as the speaker. 

 

 

 

1. Why does the author describe how some cricket species “maximize the volume of their calls”? 

 

O To argue that crickets are a major source of noise in virgin rain forests 

 

O To help explain why it is difficult for many smaller animals to be heard in rain forests 

 

O To help explain why rain forests are noisier than other natural environments 

 

O To illustrate a sophisticated way of making a call heard in a rain forest

 

 

 

2. The author mentions a “stereo speaker” in the passage in order to 

 

O contrast the ways in which humans and insects magnify their sounds 

 

O compare the ranges of sounds produced by humans and insects 

 

O support the claim that small size is a disadvantage for insects that produce calls 

 

O help explain how small insects magnify the sounds of their calls

 

 

 

 

 

Paragraph 3：A species of tree frog in Borneo has an inventive approach to getting its mating call heard over the noise. Mataphrenella sudana, which is only an inch long, has learned to exploit the sound properties of a water-filled hole in a tree in the same way that a person uses resonance, the intensification and enrichment of a sound by added vibration, in the shower to sing like a professional performer. The frog searches for a suitable hole and then partially submerges itself in the water. Its forte is the ability to adjust the frequency of its call to the size of the hole and play the tree like a musical instrument. As it sits in the hole, it begins vocalizing at different frequencies until it hits the one note that makes the hole and tree resonate. 

 

 

 

3. According to paragraph 3, which of the following is NOT part of the process that the Borneo tree frog used to make its mating call heard? 

 

O Finding a tree that has a hole of adequate size 

 

O Immersing part of its body in a water-filled hole 

 

O Aiming its call at a particular frog in a nearby tree

 

O Trying out a number of distinct call frequencies 

 

 

 

 

 

Paragraph 4：The time of day affects how sound travels in any environment, and this fact is not lost on animals and insects. Early morning and late evening produce conditions that allow sound to travel greater distances than during the middle parts of the day. Sound travels best at night, which is why the rain forest is so wonderfully noisy between dusk and dawn. For species that sleep at night, dusk and dawn are their windows of opportunity to get the best resonance and distance out of a signal. This is why animals, especially birds, tend to be more active and noisy in the early morning and late evening. The British call the phenomenon of birds singing in the early morning the dawn chorus. Because of the superior sound conditions, dusk and dawn are the times to conduct the serious business of attracting mates and defending territory. For predators, it is the best time to track down their noisy prey. 

 

 

 

4. According to paragraph 4, why do birds prefer to sing at the beginning and end of the day? 

 

O Their calls are less likely to produce echoes. 

 

O Their calls do not have to compete with the sounds of other animals. 

 

O They are less vulnerable to predators then. 

 

O The sound of their voices travels farther.

 

 

 

5. According to paragraph 4, what is a disadvantage of many birds all singing at dusk and dawn? 

 

O There is more competition from other birds at these times. 

 

O These are the safest times for birds to sleep. 

 

O It is easier for predators to locate birds when so many are making noise.

 

O There are the best times for birds to find prey. 

 

 

 

6. It can be inferred from paragraph 4 that a tropical rain forest is most quiet at 

 

O dawn 

 

O the middle of the day

 

O dusk 

 

O night 

 

 

 

 

 

Paragraph 5：Another way animals and insects ensure that their calls connect with the intended receivers is by developing their own specialized frequencies, which are determined primarily by the size of their bodies. Recently, a scientist visiting the Peruvian rain forest made an audiotape of a little of the night’s music. When he took the tape back to his lab and analyzed it, he discovered that this seemingly chaotic banquet of sound was actually highly ordered. Each animal and insect is tuned to and calling on its own species-specific frequency, in the same way that radio stations use different signals so that many stations can broadcast at the same time. 

 

 

 

7. According to paragraph 5, a scientist recently visiting the Peruvian rain forest discovered that 

 

O the specialized frequencies of the sounds made by animals are determined by their body size 

 

O the frequencies of sounds made by animals at night are generally random 

 

O animals and insects of particular species make sounds at specific frequencies

 

O animal and insect calls differ depending on whether they are heard in the laboratory or outside in nature 

 

 

 

 

 

Paragraph 6：Bernard Krause, a professor at the University of Oregon in Eugene, has found that in older tropical rain forests some species, such as the Asian paradise flycatcher, have become so specialized that their voices occupy several niches of the sound spectrum at the same time, thus laying territorial claim to several audio channels. His recordings from undisturbed rain forests around the world demonstrate a remarkable stability in the combined voices of the residents from year to year. The stability of the ambient sound gives each region a unique sound signature, or fingerprint. 

 

 

 

8. According to paragraph 6, what did the research of Professor Krause indicate about sound in rain forests? 

 

O Older rain forests have more varied sound frequencies than younger rain forests. 

 

O The patterns of sounds in rain forests are consistent over time.

 

O The speed of sound movement can be affected by the location of the rain forest. 

 

O It is difficult to distinguish the atmospheric sound patterns of rain forests in one region from those in another. 

 

 

 

 

 

Paragraph 5：Another way animals and insects ensure that their calls connect with the intended receivers is by developing their own specialized frequencies, which are determined primarily by the size of their bodies. ■Recently, a scientist visiting the Peruvian rain forest made an audiotape of a little of the night’s music. ■When he took the tape back to his lab and analyzed it, he discovered that this seemingly chaotic banquet of sound was actually highly ordered. ■Each animal and insect is tuned to and calling on its own species-specific frequency, in the same way that radio stations use different signals so that many stations can broadcast at the same time.■ 

 

 

 

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

 

Indeed, there were numerous layers of sound, each clearly distinct from the others.

 

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 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. 

 

Animal species in rain forests have developed a series of adaptations to make themselves heard. 

 

 

 

Answer Choices 

 

O Scientists have discovered that animals in rain forests adapt the length of their calls to overcome the barriers created by dense plant growth. 

 

O Many species of predators in rain forests prefer dawn rather than dusk as the best time to hear and pursue their prey. 

 

O Specialized frequencies facilitate sound transmission within species and also create regional sound environments that are highly stable.

 

O Some smaller animals that live in rain forests use special strategies to increase the volume of their calls and the distance that their calls travel. 

 

O Because time of day affects how sound travels, many animals restrict their calls to either nighttime, when sound travels best, or dusk and dawn. 

 

O Research conducted in the Peruvian rain forest indicates that well-ordered periods of sound alternate with more chaotic sound periods. 

 

 

 

答案请付费后查阅：