Unlocking the Value of Research into Mite Harvestmen

The IELTS Reading section tests a candidate’s ability to understand and interpret academic texts. One excellent example is the passage “The Value of Research into Mite Harvestmen.” This exercise showcases how the study of a relatively obscure insect can provide profound insights into earth sciences and evolutionary biology. Let’s delve into the structure and details of this specific reading task to help you better understand what to expect and how to prepare.

Actual Exam Passage

The value of research into mite harvestmen:

Few people have heard of the mite harvestman, and fewer still would recognize it at close range. This insect is a relative of the far more familiar daddy longlegs. But its legs are stubby rather than long, and its body is only as big as a sesame seed. To find mite harvestmen, scientists go to dark, humid forests and sift through the leaf litter. The animals respond by turning motionless, making them impossible for even a trained eye to pick out. “They look like grains of dirt,” said Gonzalo Giribet, an invertebrate biologist at Harvard University.

Dr. Giribet and his colleagues have spent six years searching for mite harvestmen across five continents. The animals carry a record of hundreds of millions of years of geological history, chronicling the journeys that continents have made around the Earth. The Earth’s landmasses have slowly collided and broken apart several times, carrying animals and plants with them. These species provide clues to the continents’ paths.

The notion of continental drift originally came from such clues. In 1911, the German scientist Alfred Wegener noted that fossils of similar animals and plants could be found on either side of the Atlantic. The ocean was too vast for species to travel across it on their own. Wegener speculated, correctly as it turned out, that the surrounding continents had originally been welded together in a single landmass called Pangea.

Continental drift, or plate tectonics as it is scientifically known, has helped move species around the world. Armadillos and their relatives are found in South America and Africa today because their ancestors evolved when the continents were joined. When South America and North America became connected a few million years ago, armadillos spread north as well. Biogeographers learn clues about continental drift by comparing related species. However, they must also recognize cases where species have spread for other reasons, such as crossing great stretches of water. For instance, Hawaii was once home to a giant flightless goose, now extinct. Studies on DNA extracted from its bones show that it evolved from the Canada goose. This evolution occurred half a million years ago, when geologists estimate that Hawaii emerged from the Pacific.

When species jump around the planet, their histories blur. It is difficult to say much about where cockroaches evolved because they can move quickly from continent to continent. This process, known as dispersal, limits many studies. “Most studies tend to concentrate on particular parts of the world,” Dr. Giribet said. “I wanted to find a new system for studying biogeography on a global scale.”

Dr. Giribet realized that mite harvestmen might be that system. The ~5,000 mite harvestmen species can be found on every continent except Antarctica. Unlike creatures found globally like cockroaches, mite harvestmen cannot disperse well. The typical harvestman species has a range of fewer than 50 miles. They are not found on young islands like Hawaii, which emerged long after the breakup of Pangea. According to Assistant Professor Sarah Boyer, a former student of Dr. Giribet, “It’s really hard to find a group of species that is distributed all over the world but also doesn’t disperse very far.”

What mite harvestmen lack in mobility, they make up in age. Their ancestors were among the first land animals, and fossils of daddy longlegs have been found in 400 million-year-old rocks. Mite harvestmen evolved long before Pangea broke up and have been carried along by continental drift ever since. They’ve managed to get around the world only because they’ve been around for hundreds of millions of years,” Dr. Boyer said.

Dr. Boyer, Dr. Giribet, and their colleagues have gathered thousands of mite harvestmen from around the world, extracting DNA. Variations in the genes helped scientists build an evolutionary tree. By calculating how quickly the DNA mutated, scientists could determine when lineages branched off. They compared the harvestmen’s evolution to the movements of the continents. “The patterns are remarkably clear,” Dr. Boyer said.

The scientists found they could trace mite harvestmen to their ancestors on Pangea. One lineage includes species in Chile, South Africa, Sri Lanka, and other places separated by thousands of miles of ocean. But 150 million years ago, all those sites were in Gondwana, a region of Pangea. The harvestmen preserve smaller patterns of continental drift as well. After analyzing the DNA of a Florida harvestman, Metasiro americanus, scientists were surprised to find that it was not related to other North American species. Its closest relatives live in West Africa. Dr. Boyer began investigating Florida’s geological history and found recent research explaining the mystery. Florida started welded to West Africa near Senegal. North America then collided with this region as Pangea formed. About 170 million years ago, North America ripped away from West Africa, taking Florida with it. The African ancestors of Florida’s harvestmen came along for the ride.

Dr. Giribet now hopes to study dozens or even hundreds of species to find clues about plate tectonics that a single animal could not show.

Mite Harvestman

Reading Answers

1. Questions 27-32

   • 27 (C. They are hard to distinguish from their surroundings): Why is it difficult to find mite harvestmen?
   • 28 (D. They provide evidence relating to a field of study other than insects): Why are mite harvestmen of interest to Dr. Giribet and his colleagues?
   • 29 (B. The distance that species could travel): What factor contributed to Wegener’s idea that present-day continents used to form a single landmass?
   • 30 (A. Regions have both separated and become connected): What point is made by the reference to armadillos?
   • 31 (D. The Hawaiian goose became flightless after it had reached Hawaii): Which of the following is stated in the fifth paragraph?
   • 32 (A. They spread too fast): Why is evidence from cockroaches of limited value?

2. Questions 33-36

   • 33 (NO): The colonization of Hawaii by geese provides evidence of continental drift.
   • 34 (YES): The reason why mite harvestmen don’t exist on Hawaii can be explained.
   • 35 (NOT GIVEN): The DNA of certain species has evolved more quickly than that of others.
   • 36 (NOT GIVEN): Dr. Boyer’s theory concerning the origins of Florida is widely accepted.

3. Questions 37-40

   • 37 (H – ancestors): Some of the first creatures to live on land were the ancestors of mite harvestmen.
   • 38 (D – DNA): Boyer, Giribet, and others study differences in the DNA of these insects.
   • 39 (A – branches): They trace the development of a number of branches of the species.
   • 40 (I – continents): Their evolution appears to reflect changes in the location of continents.

Common Errors in This Type of IELTS Question

• Misinterpreting Details: Candidates often mix up specific details about when and where certain species evolved or dispersed.
• Overlooking Keywords: Missing key terms that hint at the correct answer.
• Not Understanding Question Format: Some candidates struggle with different types of IELTS reading questions, such as True/False/Not Given versus Multiple Choice.

Challenging Vocabulary in the Passage

1. Relative (of) (n.) – A connected organism or species: “The mite harvestman is a relative of the daddy longlegs.”
2. Stubby (adj.) – Short and blunt: “The mite harvestman has stubby legs.”
3. Sift through (v.) – To search by passing through: “Scientists sift through leaf litter to find mite harvestmen.”
4. Geologist (n.) – Scientist who studies earth processes: “The story told by mite harvestmen is of interest to geologists.”
5. Evolve (v.) – Develop over successive generations: “The Canada goose evolved into the giant flightless goose.”
6. Dispersal (n.) – The act or process of distributing: “This process, known as dispersal, limits many studies.”

Important Grammar Structures to Note

1. Passive Voice – Often used in scientific texts as observed in: “Mite harvestmen cannot be distinguished…”

   • Example: Fossils of daddy longlegs have been found in 400 million-year-old rocks.

2. Conditional Sentences – Frequently used to link causes and effects: “If the DNA mutates faster, scientists can determine the branch timelines more accurately.”

   • Example: When species jump around the planet, their histories blur.

Employing these structures and familiarizing yourself with academic vocabulary are key strategies for excelling in the IELTS Reading section.

By understanding these components, IELTS candidates can improve their reading comprehension and answer questions more accurately. Use this guide to navigate similar passages effectively and boost your IELTS score.