elearn site

 
IELTS COURSES --> IELTS PRACTICE --> ACADEMIC READING
 Taking soundings
 
A Until recently it was thought that dolphins, porpoises and bats were the only mammals to use echolocation to locate prey and to navigate their environment. New research suggests that ‘great whales’, like the blue whale and the humpback whale, might be able to ‘see’ in a similar way. Underwater sound recordings of humpback whales have captured sonar clicks similar to those made by dolphins.
 
B The ability of ‘great whales’ to use sound to communicate has been known for decades. In deep water, where light cannot penetrate, whales use sound like we use our eyes. Low frequency vocalizations, in the form of grunts and moans are inaudible to the human ear, but form a pattern or song that enables whales to recognize their own species. Blue whales are the loudest animals on earth and their sounds can travel for hundreds of kilometres. Highly sensitive hearing allows whales to avoid shipping and to orientate themselves to the land by listening to waves crashing on the shore. Whales might also use sound to detect the seabed or polar ice packs by listening to the echoes of their own whale song. Man-made ocean sound, or ‘noise pollution’, can drown out whale calls. Increasing amounts of background noise from motorized shipping and from oil and gas drilling is making it difficult for whales to communicate and navigate via sound.
 
C Echolocation, also called bisonar, is a different form of sensory perception. A dolphin, for example, sends out a series of short clicks and waits for an echo to be reflected back from the obstacle or prey. Both the size and distance of an object can be determined from the echo. The clicks, known as ultrasound, consist of high-pitch (frequency) sound waves, well above the range of the human ear, and distinct from the low-pitched whale song. Whilst there is evidence supporting the use of ultrasound by whales, it has not been shown that they can use echolocation. Instead, the clicks might serve to scare and control shoals of small fish on which some whales prey.
 
A major concern of environmentalists is that high-power military sonar might disorientate or harm whales, and that it is responsible for the mass strandings seen on beaches. However, whales were beaching themselves before the invention of sonar and evidence from fossils indicates that stranding goes back thousands of years. Today though, stranding occurs more frequently in waters where navy training exercises take place. The impact of man-made sonar on the stranding of whales and dolphins can no longer be ignored. Following pressure from environmentalists, US law requires that the navy take steps to minimize the effects of sonar on mammals wherever possible. Most of these precautions are common sense and include avoiding whale migration routes when whales are present, not operating the sonar when dolphins are riding a bow wave, and checking to see if a stranding has taken place after sonar has been deployed.
 
E The phenomenon of stranding is not well understood but it can occur for entirely natural reasons. One explanation involves the ability of whales, like many animals, to use the earth’s magnetic field for direction finding. Ocean currents are thought to cause fluctuations in the earth’s magnetic field, which may leave whales vulnerable to navigation errors when they migrate to their breeding grounds. Other reasons for stranding include straying into shallow coastal water when following prey, or when attempting to escape predators such as killer whales. Sea currents, winds and storms are all known to play their part. When a single whale is found dead on a beach it might have died from natural causes out at sea and been washed up on shore. It is apparent that multiple deaths at sea cannot produce a ‘mass stranding’ on a single beach because the carcases would have washed up along different parts of the shoreline. In these circumstances there is concern that the multiple deaths may be man-made, linked to marine pollution, over-fishing, which deprives the whales of food, or entanglement with nets. However, a mass stranding of whales on a single beach, like those shown on television, can also arise naturally. Whales are social animals that swim in groups known as ‘pods’. Some scientists have speculated that if a sick or injured whale takes refuge in shallower water the rest of the pod might follow on to become trapped when the tide goes out.

The reading passage has five paragraphs A to E. Which paragraph contains the following information?


1. an example of sound being used other than for navigation and location of prey
A. Paragraph B
B. Paragraph D
C. Paragraph E
D. Paragraph A
E. Paragraph C
Explain:


2. examples of mammals other than whales and dolphins that use echolocation
A. Paragraphs A
B. Paragraph B
C. Paragraph E
D. Paragraph C
E. Paragraph D
Explain:


3. how man′s behavior has increased the number of whales being stranded
A. Paragraphs D
B. Paragraph E
C. Paragraph B
D. Paragraph A
E. Paragraph C
Explain:


4. an example of whales living in a community
A. Paragraph C
B. Paragraph D
C. Paragraphs E
D. Paragraph A
E. Paragraph B
Explain:


5. why people cannot hear whale song.
A. Paragraphs B
B. Paragraph C
C. Paragraph E
D. Paragraph A
E. Paragraph D
Explain:

 Complete the summary below. Choose NO MORE THAN TWO WORDS from the passage for each answer.


1.
training exercises major concern common sense migration routes


The harmful effects of high-power sonar on whales are a  . It is recognized that the navy pose a threat to whales during   when the number of beachings have been observed to increase. The impact of sonar on mammals can be lessened by taking a number of   steps. For example, it is clear that ships with sonar equipment should keep away from whale  .


 Complete the summary below. Choose ONLY ONE WORD from the passage for each answer.


1.
social cannot predators navigation


Several reasons, not linked with human activities, have been proposed to explain why whales beach themselves. Changes in the earth′s magnetic compass can lead to mistakes in  . Alternatively, whales might stray into shallow water when pursued by  , or to chase prey, and then become trapped by the tide. Whilst one whale on a beach might have died naturally out at sea and been washed ashore, a group of whales   because their bodies would appear on different stretches of sand. ‘Mass stranding′ appears to be linked to the   nature of whales and their tendency to swim into shallow water as a group.


Total: 65 page(s)
Score: 0/10
No.DateRight ScoreTotal Score
 
PARTNERS
NEWS
Khai giảng lớp học tiếng anh miễn phí cho trẻ em nghèo

Triển khai chương trình hoạt động xã hội nhằm tích cực đóng góp cho cộng đồng

Báo Doanh Nhân Sài Gòn viết về trang web elearn.edu.vn

"Better English, Better Choice" (tạm dịch: Tiếng Anh tốt hơn, Lựa chọn tốt hơn) là khẩu hiệu của website ôn luyện tiếng Anh trực tuyến http://elearn.edu.vn.

 

BEES Group
Address: 57/8A Đường số 3, KP1, P.Tăng Nhơn Phú B, Q.9, TP.HCM
Tel: 0932 727 818
Copyright 2010-2020 - All Rights Reserved