IELTS READING LEVEL 7.5 – Naturally Selected to Survive

Naturally Selected to Survive

by Michael Stahl

 

 

The earth has changed, over and over again, throughout the course of its history. Some of these changes have happened quickly. Others have occurred over long stretches of time. For example, the planet has experienced ice ages that took place over thousands of years. During those eras, huge sheets of ice covered much of the surface of the globe. Then for a few thousand years between the ice ages, the earth warmed up. Scientists believe that this cycle has actually occurred a few times.

As the planet goes through this cycle, environments may go through changes. In order to survive in changing environments, species oftentimes must undergo a process of adaptation. Adaptation refers to a mutation or genetic change that enables an organism such as an animal or plant to survive in its environment. This trait is passed down from one generation to the next, becoming an inherited trait of the species. A species may have to adapt to warmer temperatures, increased precipitation, or even developing air pollution. If the organisms of a species cannot change along with the area in which they live, they risk dying out. Though an uncountable number of species that have roamed the earth have become extinct, the planet has seen many others adapt as well. These select organisms have been able to go on living in their environment.

A species adapts to a changing environment as organisms with favorable traits reproduce and survive. These favorable traits, which help the species survive, are passed down through different generations of the species. This process is called “natural selection.” Recent history has given us an important example of how organisms are able to survive once their environments change.

Light gray peppered moths and dark-colored peppered moths lived in the countryside between the cities of Manchester and London in England. Many years before the 19th century, more of the light gray peppered moths had been able to survive in their environment mostly because of their color.

Their thin layer of skin, as well as their large wings, was mostly gray with a little bit of black “peppered” all around. This color was advantageous because the light gray peppered moths were camouflaged when they stayed on gray-colored areas on the sides of trees in their habitat. Predators, which were mostly birds, could not see the light-colored moths on the trees because the color of the moths blended in with the color of the trees. Instead, the predators were able to see the dark-colored peppered moths more easily.

In the early 19th century, though, England began the first years of its Industrial Revolution. Many areas, especially in and between the cities of Manchester and London, became populated by a growing number of factories. This was because companies began to use a lot of new machinery that had been invented in the decades before. These machines made work a lot easier in many ways. The companies could build more products faster than ever before. However, many of these factories needed coal to provide energy for the machines. When coal burns, it gives off a lot of dark-colored smoke. Soot is a black substance that collects on a surface that comes into contact with smoke. Smoke’s dark particles stick onto surfaces like paint. In the English countryside near industrialized areas, the trees began to blacken with soot because of all of the smoke in the air from the factories. This made the light gray peppered moths much more vulnerable. Predators could see them on the trees more clearly and easily hunt them down.

Sometime in the next hundred years, scientists began to notice a huge change in the moth population living in and between the cities of Manchester and London near where many of those factories had been constructed. Most of the peppered moths were the dark-colored kind! What caused this change was the fact that predators had eaten a lot of the light gray peppered moths because the moths were clearly visible on the black-colored trees. The dark-colored peppered moths in the area survived much more easily and mated with other dark-colored peppered moths until most of the population of peppered moths became dark-colored.

Many scientists feel that this example of evolution in a species supports Charles Darwin’s theory of natural selection. An author named J.W. Tutt published a report about the moths a few years after Darwin’s death, writing that the change in the peppered moth population seemed to support Darwin’s ideas. Though Darwin was not alive to read the Tutt report, his teachings about nature live on.


Vocabulary

 

adapt       a ·dapt

Advanced Definition

transitive verb

  1. to make fit or suitable for a particular need or condition; adjust.

They adapted the reading room so they could hold meetings there.

The school water fountains are adapted for children.

intransitive verb

  1. to become adjusted.

The children of the immigrants adapted quickly to their new surroundings.

Spanish cognate

adaptar: The Spanish word adaptar means adapt.

These are some examples of how the word or forms of the word are used:

  1. One by one, the other races have gone extinct. The hypothesized reasons range from an inability to adapt to climate change to murder at the hands of more advanced humans.
  2. Natural selection allows animals that have traits best suited to a particular environment to survive and produce offspring. Animals who are unable to adapt to changes in their environments die off
  3. Another interesting variable that lets organism populations adapt to changing environments is mutation in genes. Sometimes, unpredictable changes in genetic code will appear within a new generation, not traceable back to a parental source.
  4. Conservative Jews believe in the traditional beliefs and values of Judaism. The difference is that they adapt these beliefs to fit the times. This form of Judaism was developed in the mid 1800s. Conservative Jews follow many of the same rules as Orthodox Jews. However, they are more willing to change the rules if they feel it is needed.
  5. Darwin’s theory teaches us that an animal or plant thatadapts to its environment and remains alive long enough to procreate will thrive. The dodo bird, which has gone extinct, was not lucky in this respect. A lack of predators for thousands, and maybe even millions, of years meant that the dodos never learned to fly. When humans finally arrived to their home on the island of Mauritius, the dodos had no way of protecting themselves and, in the 17th century, were wiped out.
  6. But Emine was determined to adapt to the city’s frenetic energy. On her first evening in Cairo, she took a stroll from her hotel to the banks of the Nile, and watched the boats bobbing lazily on the water. Away from the traffic, people strolled and laughed quietly; the palm trees whispered in the wind, and Emine felt calmer.
  1. Zoe had specialized in behavioral ecology during her studies at university, so when she applied for a job at the zoo, she specified that she was very interested in the ways animals adapt their behavior to changing environmental factors.
  1. Many of these species are endemic to tropical rainforests, meaning that rainforests are the only place they live on Earth. Some have had to adapt to their surroundings in order to survive. For example, toucans and parrots both have very large, strong beaks. These powerful beaks make it easy for them to crack open the tough shells of nuts that grow on many rainforest trees.
  2. Before the breakup of Pangaea, many scientists believe, all of life was situated in one ecosystem, and did not have any reason to adapt to change. Once Pangaea broke up, it was possible for evolution to happen at an increased rate.

 

camouflage       cam ·ou ·flage

Advanced Definition

noun

  1. a method of concealing something such as a person, vehicle, or building, esp. from an enemy military force, by covering it or coloring it so as to imitate its surroundings.

Camouflage is crucial to the defense of any army.

The coats of many animals serve them as a natural form of camouflage.

  1. the material, such as paint, fabric, or foliage, used to conceal something by this method.

The soldiers covered their vehicles with camouflage.

  1. any method of disguising for the purpose of concealing.

His apparent calmness was camouflage for his real fears.

transitive verb

  1. to conceal by coloring or covering to imitate the surroundings.

In winter the soldiers camouflaged themselves by wearing white.

  1. to conceal by disguising.

She camouflaged her true motives.

Spanish cognate

camuflaje: The Spanish word camuflaje means camouflage.

These are some examples of how the word or forms of the word are used:

  1. The peppered moth was light in color and had speckled wings. It was hard to pick out against many of the trees and buildings in England and could camouflage itself easily.
  2. Startled onlookers watched as a veiled chameleon climbed up a tree branch and changed color. The chameleon’s ability tocamouflage, or conceal itself by changing its appearance, helps the creature hide from predators and curious museum-goers.
  3. The okapi is only one-third as tall as a giraffe with a shorter neck. It’s also a solitary animal; except for mothers and infants, okapis keep to themselves. And then there are the zebra-like stripes on its legs and hind flanks, which serve as camouflage. Camouflage is a disguise that protects an animal from predators-in the okapi’s world, leopards.
  1. Penguins are a type of bird that live mostly in water. Their black and white appearance is known as countershading, which is a form of camouflage that helps keep them safe in the water.
  1. Another way animals adapt to life in the rainforest is by camouflaging themselves to hide from predators. An insect called the “walking stick” lives in the palm tree, and it blends in so well with it that it’s practically unnoticeable unless it moves. When they close their wings, some butterflies look identical to leaves, which masks them from predators.

Name: ___________________________________ Date: _______________
Comprehension Questions
1. According to the text, what happens when organisms cannot adapt to changes in their environment?
A. They move to another environment.
B. They risk dying out.
C. Nothing happens.
D. They wait for the environment to change again.
2. What does the author mainly describe in the text?
A. how natural selection changed the population of peppered moths
B. how the Industrial Revolution improved the lives of workers
C. how Charles Darwin devised his theory of natural selection
D. how humans influence organisms via artificial selection
3. Smoke given off by the factories threatened the survival of the light gray peppered moths. What evidence from the text best supports this conclusion?
A. Soot is a black substance that collects on a surface that comes into contact with smoke.
B. When coal burns, it gives off a lot of dark-colored smoke.
C. Predators could see the light gray peppered moths on the black trees covered by soot and easily hunt them down.
D. The trees began to blacken with soot because of all of the smoke in the air from the factories.
4. What conclusion can be drawn from the change in population of light gray peppered moths and dark-colored peppered moths?
A. The color change had nothing to do with the change in environment.
B. There were previously no dark-colored peppered moths.
C. The lighter peppered moths migrated to a new environment.
D. Darker coloring is currently better for the peppered moth’s survival.
5. What is this text mostly about?
A. Charles Darwin
B. the Industrial Revolution
C. natural selection
D. Earth’s ice ages
6. Read the following sentences: “In the English countryside near industrialized areas, the trees began to blacken with soot because of all of the smoke in the air from the factories. This made the light gray peppered moths much more vulnerable. Predators could see them on the trees more clearly and easily hunt them down.”
What does “vulnerable” mean?
A. quick to change
B. open to attack
C. easily defended
D. in a strong position
7. Choose the answer that best completes the sentence below.
___________ of the smoke given off by coal burned in the factories, the nearby trees
became blackened with soot.
A. On the other hand
B. Primarily
C. As an illustration
D. As a result
5. What is this text mostly about?
A. Charles Darwin
B. the Industrial Revolution
C. natural selection
D. Earth’s ice ages
6. Read the following sentences: “In the English countryside near industrialized areas, the trees began to blacken with soot because of all of the smoke in the air from the factories. This made the light gray peppered moths much more vulnerable. Predators could see them on the trees more clearly and easily hunt them down.”
What does “vulnerable” mean?
A. quick to change
B. open to attack
C. easily defended
D. in a strong position
7. Choose the answer that best completes the sentence below.
___________ of the smoke given off by coal burned in the factories, the nearby trees
became blackened with soot.
A. On the other hand
B. Primarily
C. As an illustration
D. As a result
8. What is natural selection?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
9. How did the peppered moth’s environment change, and what caused this change?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
10. How did the peppered moth population become mostly dark-colored?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________

ReadWorks.org · © 2013 ReadWorks®, Inc. All rights reserved.

 

Phụ huynh và học viên có thể xem đáp án (answer key) và download file PDF tại đây

Trả lời

Email của bạn sẽ không được hiển thị công khai. Các trường bắt buộc được đánh dấu *

Call Now Button