READING PASSAGE 2:

You should spend about 20 minutes on Questions 14 – 26, which are based on Reading Passage 2 on pages 6 and 7

The horseshoe crab

A

One of the world’s oldest animal species, the horseshoe crab, is found along the

east coast of the United States and Mexico. Fossil records indicate this creature dates

back 450 million years, and it has changed very little over time. This is because its

anatomy has been so successful. In fact, the horseshoe crab is more closely related to

spiders, scorpions and ticks than it is to true crabs and other crustaceans.

B

The soft body of the horseshoe crab is protected by a large oval shell with

jagged, point spines. The two-part body consists of a head and an abdominal region.

The head region contains a brain, heart, mouth, four eyes and six pairs of legs. What is

significant is that horseshoe crabs possess the rare ability to regrow lost limbs. They

also use crawling as their primary means of movement, and commonly bury themselves

under the surface of the sand. However, in the water, they will occasionally turn onto

their backs and swim upside-down. The mouth of the horseshoe carb is located

between the twelve legs. They can only eat when crawling, as the motion allows them to

open and close their mouths. Their diet consists mainly of worms and clams.

The abdominal region contains mules far movement and is for breathing. A long

spine forming a tail, called a telson, is located behind the abdominal region. Although

this part of the body looks intimidating, it is not dangerous, poisonous or used to sting.

Horseshoe crabs use it to flip over if they happen to be pushed on their backs, but this

is only possible under the sea. Every year, about 10 percent of the horseshoe crab

breeding population dies while on the beach, when rough surf flips the creatures onto

their backs, a position from which they often cannot right themselves.

C

Another distinctive feature of horseshoe crabs is that they do not have

hemoglobin (a protein that contains the mineral iron), which gives blood its red color.

Hemoglobin is the basis of oxygen transport in the blood of mammals, reptiles and

birds. Rather, the blood of horseshoe crabs has a copper-containing protein called

hemocyanin. Hemocyanin is dark blue when it is transporting oxygen and colorless

when it is not. The oxygen is also transported in a fluid on the exterior of the cell, in

contrast to most animals, where oxygen molecules are transported inside red blood

bacteria and fungi. In fact, there enzymes are used by astronauts in the International

Space Station to test surfaces for unwanted bacteria and fungi. Another application is a

protein from horseshoe crab blood that is under investigation as an antibiotic.

D

The horseshoe crab faces the greatest dangers in early life. Between April and

June, adult horseshoe crabs travel from deep ocean waters to converge on beaches.

Crawling out of the sea and onto the beach is especially common at high tides during

full and new moons. The males arrive first and await the females for breeding. Female

horseshoe crabs communicate by releasing a scent to signal to the males.

The female horseshoe crabs crate nests by digging holes in the sand and laying

between 60000 and 120000 eggs at a time before covering them with sand for

Protection. Most eggs do not survive the hatching period before being eaten, as the

eggs are a food source for numerous birds, reptiles and fish.>> Form đăng kí giải đề thi thật IELTS 4 kĩ năng kèm bài giải bộ đề 100 đề PART 2 IELTS SPEAKING quý đang thi (update hàng tuần) từ IELTS TUTOR

E

If the egg does survive, the young horseshoe cab will hatch after five weeks.

Referred to as larvae, they look like miniature versions of adult horseshoe crabs. When

first entering the sea, they exhibit a ‘swimming frenzy’ similar to that of newborn sea

turtles, swimming vigorously and continuously for hours. During the larval stage, which

can last a year or more, newly hatched horseshoe crabs travel into the ocean water and

settle on the sandy bottom in shallow waters. As they develop, they move into deeper

waters.

After the larval stage, horseshoe crabs move into the juvenile period. The

juvenile horseshoe crabs will slowly grow over a period of about ten years. The growing

process requires shedding small exterior shells, known as exoskeletons, in exchange

for larger shells. Horseshoe crabs can shed up to 17 exoskeletons during development

and their can reach 45-50 centimeters from head to tail, while the males grow to

approximately 35-40 centimeters.

F

Despite their long history, horseshoe crabs face increased threats in modern

times. For this reason, scientists have been studying the populations of horseshoe

crabs, but more investigation is needed, particularly on the coast of Florida. A

widespread decline in their abundance in the last 20 years may be especially severe in

the Indian River Lagoon system in Florida, while the horseshoe crab is not currently

listed as threatened, there is rising concern about the fact that it is increasingly absent

from the Indian River Lagoon system, where it has historically been common. Loss of

the horseshoe crab would negatively impact species that feed on the animal and its

eggs and would decrease the biodiversity of the lagoon. Moreover, his development

might indicate serious ecological disturbance in the region. In the northeast, the use of

horseshoe crabs as bait to catch fish over the past ten years is, in part, responsible for a

rapidly declining population of this unique species, and it is suspected that this is also a

problem in Florida. However, the extent of this has not been well documented

Questions 14 – 18

Reading Passage 2 has six sections, A – F

Which section contains the following information?

Write the correct letter, A – F in boxes 14 – 18 on your answer sheet.

NB You may use any letter more than once.

14 a mention of the horseshoe crab’s potential value in medical science

15 an explanation of the function of the horseshoe crab’s tail>> IELTS TUTOR có hướng dẫn kĩ SỬA BÀI IELTS WRITING TASK 2 ĐỀ THI THẬT NGÀY 22/8/2020 của HS IELTS TUTOR đạt 6.5 Writing

16 a reference to the horseshoe crab’s feeding habits

17 a description of horseshoe crab reproduction

18 an account of the horseshoe crab’s development to adulthood

Questions 19 and 20

Choose TWO letter, A – E Write the correct letters in boxes 19 and 20 on your answer sheet. According to the writer, which TWO of the following are true about the characteristics of horseshoe crabs?

A They bury themselves upside down.

B They must continue moving while eating.

C They most commonly move by swimming.

D They are able to replace their missing legs.

E They breathe through their mouth while on land.

Questions 21 and 22

Choose TWO letter, A – E Write the correct letters in boxes 21 and 22 on your answer sheet. According to the write, in which TWO ways is horseshoe crab blood different from that of most other animals?

A It has a different mineral composition.

B It lack a bacteria – fighting protein.

C Harmless fungi regularly grow in the blood.

D Its colour changes from blue to red as it circulates.

E The blood cell carries oxygen its surface.

Question 23-26

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

The horseshoe crab in Florida

A study of the Indian River Lagoon system in Florida has shown a 23 …………….. in the horseshoe crab’s population. This means that animals that eat both horseshoe crabs and their 24 ……………… could also be impacted. The result would affect the Indian River Lagoon system’s 25 ……………… Local fishmen taking horseshoe crabs for 26 ……………… could be one cause of the reduction in numbers.