In the IELTS reading segment, you will be given 3 to 4 reading topics to read and a series of questions to answer. The passage will always be the source of the questions. You have 60 minutes to complete all of the passages and answer all of the questions.
Now let’s get down to business and learn how to answer the questions. Read the when evolution runs backwards reading answers topic and try to answer the sample questions without looking at first.
When Evolution Runs Backwards Reading Answers
In the following sections, you will go through the main topic’s passages along with a set of different question types. You can check your speed and efficiency by answering them on your own. Now, let’s get started.
When Evolution Runs Backwards Reading Answers Paragraph A
Evolution isn’t supposed to run backwards – yet an increasing number of examples show that it does and that it can sometimes represent the future of a species.
The description of any animal as an ‘evolutionary throwback’ is controversial. For the better part of a century, most biologists have been reluctant to use those words, mindful of a principle of evolution that says ‘evolution cannot run backwards. But as more and more examples come to light and modern genetics enters the scene, that principle is having to be rewritten. Not only are evolutionary throwbacks possible, they sometimes play an important role in the forward march of evolution.
They reasoned that while some evolutionary changes involve the loss of genes and are therefore irreversible, others may be the result of genes being switched off. If these silent genes are somehow switched back on, they argued, long-lost traits could reappear.
When Evolution Runs Backwards Reading Answers Paragraph B
The technical term for an evolutionary throwback is an ‘atavism’, from the Latin atavus, meaning forefather. The word has ugly connotations thanks largely to Cesare Lombroso, a 19th-century Italian medic who argued that criminals were born not made and could be identified by certain physical features that were throwbacks to a primitive, subhuman state.
While Lombroso was measuring criminals, Belgian palaeontology called Louis Dollo was studying fossil records and coming to the opposite conclusion. In 1890 he proposed that evolution was irreversible: that ‘an organism is unable to return, even partially, to a previous stage already realised in the ranks of its ancestors.
When Evolution Runs Backwards Reading Answers Paragraph C
Early 20th-century biologists came to a similar conclusion, though they qualified it in terms of probability, stating that there is no reason why evolution cannot run backwards -it is just very unlikely. And so the idea of irreversibility in evolution stuck and came to be known as ‘Dollo’s law.
If Dollo’s law is right, atavisms should occur only very rarely, if at all. Yet almost since the idea took root, exceptions have been cropping up. In 1919, for example, a humpback whale with a pair of leglike appendages over a metre long, complete with a full set of limb bones, was caught off Vancouver Island in Canada. Explorer Roy Chapman Andrews argued at the time that the whale must be a throwback to a land-living ancestor. ‘I can see no other explanation, ‘he wrote in 1921.
When Evolution Runs Backwards Reading Answers Paragraph D
Since then, so many other examples have been discovered that it no longer makes sense to say that evolution is as good as irreversible. And this poses a puzzle: how can characteristics that disappeared millions of years ago suddenly reappear? In 1994, Rudolf Raff and colleagues at Indiana University in the USA decided to use genetics to put a number on the probability of evolution going into reverse.
The team calculated that there is a good chance of silent genes surviving for up to 6 million years in at least a few individuals in a population, and that some might survive as long as 10 million years. They reasoned that while some evolutionary changes involve the loss of genes and are therefore irreversible, others may be the result of genes being switched off. If these silent genes are somehow switched back on, they argued, long-lost traits could reappear.
When Evolution Runs Backwards Reading Answers Paragraph E
Raff’s team went on to calculate the likelihood of it happening. Silent genes accumulate random mutations, they reasoned, eventually rendering them useless. So how long can a gene survive in a species if it is no longer used?
The team calculated that there is a good chance of silent genes surviving for up to 6 million years in at least a few individuals in a population and that some might survive as long as 10 million years. In other words, throwbacks are possible, but only to the relatively recent evolutionary past.
As a possible example, the team pointed to the mole salamanders of Mexico and California. Like most amphibians these begin life in a juvenile ‘tadpole’ state, then metamorphose into the adult form – except for one species, the axolotl, which famously lives its entire life as a juvenile.
When Evolution Runs Backwards Reading Answers Paragraph F
The simplest explanation for this is that the axolotl lineage alone lost the ability to metamorphose, while others retained it. From a detailed analysis of the salamanders’ family tree, however, it is clear that the other lineages evolved from an ancestor that itself had lost the ability to metamorphose. In other words, metamorphosis in mole salamanders is an atavism. The salamander example fits with Raff’s 10million-year time frame.
More recently, however, examples have been reported that break the time limit, suggesting that silent genes may not be the whole story. In a paper published last year, biologist Gunter Wagner of Yale University reported some work on the evolutionary history of a group of South American lizards called Bachia.
When Evolution Runs Backwards Reading Answers Paragraph G
Many of these have minuscule limbs; some look more like snakes than lizards and a few have completely lost the toes on their hind limbs. Other species, however, sport up to four toes on their hind legs. The simplest explanation is that the toed lineages never lost their toes, but Wagner begs to differ.
According to his analysis of the Bachia family tree, the toed species re-evolved toes from toeless ancestors and, what is more, digit loss and gain have occurred on more than one occasion over tens of millions of years.
So what’s going on? One possibility is that these traits are lost and then simply reappear, in much the same way that similar structures can independently arise in unrelated species, such as the dorsal fins of sharks and killer whales.
When Evolution Runs Backwards Reading Answers Paragraph H
Another more intriguing possibility is that the genetic information needed to make toes somehow survived for tens or perhaps hundreds of millions of years in the lizards and was reactivated. These atavistic traits provided an advantage and spread through the population, effectively reversing evolution.
But if silent genes degrade within 6 to million years, how can long-lost traits be reactivated over longer timescales? The answer may lie in the womb. Early embryos of many species develop ancestral features.
Snake embryos, for example, sprout hind limb buds. Later in development these features disappear thanks to developmental programs that say ‘lose the leg’. If for any reason this does not happen, the ancestral feature may not disappear, leading to an atavism.
IELTS Reading Answers Questions
Here is a set of questions with answers from the above passage. By going through them, you will get an idea about the types of questions that can be asked in your IELTS exam. We have covered three types of questions in this section:
#1. Fill in the blanks
#3. True or false
IELTS Exam Fill in the Blanks Questions
In the questions below, you will have to fill the gaps with the relevant word from the given passage.
Q. Because of ________ , a 19th-century Italian physician who claimed that criminals were born, not produced, and could be detected by physical characteristics that harken back to a primordial, subhuman existence, the phrase has a negative connotation.
Ans. Cesare Lombroso
Q. An evolutionary throwback is known as a ‘ ________,’ which comes from the Latin word atavus, which means forefather.
Q. The most straightforward explanation is that only the axolotl lineage lost its capacity to ________ , while others kept it.
Q. The toed species re-evolved toes from toeless ancestors, as per his research of the ________, and digit loss and gain occurred on several occasions over tens of millions of years.
Ans. Bachia family tree
IELTS Exam Questions: Vocabulary
In the questions below, you will have to answer the antonyms and synonyms of the words from the given passage.
Q. Synonym of achieve
Q. Synonym of quarantine
Q. Synonym of valid
Q. Synonym of pacify
Q. Synonym of recalcitrant
Q. Antonym of important
Q. Antonym of simple
Q. Antonym of straight
Q. Antonym of demand
Q. Antonym of grow
True or False Questions for IELTS Preparation
In the questions below, you will have to check if the statement is true or false by comparing it to the given passage.
Q1. Raff’s team then calculated the chances of it happening. They reasoned that silent genes accrue random mutations, ultimately rendering them worthless.
Q2. Because of Cesare Lombroso, a 18th-century Italian physician who claimed that criminals were born, not produced, and could be detected by physical characteristics that harken back to a primordial, subhuman existence, the phrase has a negative connotation.
Q3. Early 19th century scientists reached a similar result, albeit they tempered it by saying that there is no reason why evolution can’t go backwards.
Q4. Silent genes have a strong probability of surviving for up to 6 million years in at least a few individuals in a community, and some may survive for up to 10 million years, according to the researchers.
Q5. Rudolf Raff and colleagues at Indiana University in the United States decided to use genetics to calculate the likelihood of evolution going backwards in 1994.
Some IELTS Exam Day Tips
#1. The test is very long, therefore, you must take good rest and food the day before the main exam.
#2. Wear comfortable clothes on exam day. This will help you feel relaxed through the exam
#3. You can drink water during the test. Make sure to bring a transparent bottle for that.
#4. Always arrive early at the exam centre. Sometimes you might get stuck in the traffic or getting directions.
#5. Double-check on taking all the required IDs and documents for the exam.
We hope that this reading passage topic helped you in adding a plus point in your preparation journey. So, could you answer the questions without looking? If yes, you are doing the right kind of practice. If not, you must practice reading more topics.
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