Life At The Limit - IELTS Reading Answers & Explanations
From Collins Practice Tests For IELTS 3 Academic Reading Test 1 · Part 3 · Questions 29–40
Reading Passage
You should spend about 20 minutes on Questions 29-40, which are based on Reading Passage 3 below.
Life at the limit
What are the physical limits to life in extreme environments? Although microbes are the Earth's simplest organisms, they live in places where it is impossible for more complex life forms to survive. Some microbes are able to thrive in the water surrounding deep sea hydrothermal vents, which emit water heated up to 400°C. At the other extreme, some microbes can survive in sub-zero temperatures. In fact, marine microbes living in all regions of the ocean make up over 98% of the total organisms living in the ocean. But what exactly are the limits to survival? Can organisms live in places that lack nutrients, and how long can they survive?
The middle of the Pacific Ocean, in an area known as the South Pacific Gyre, is the place furthest from any land, and it lacks nutrients or signs of life. According to Steven D'Hondt, an oceanographer at the University of Rhode Island, it is the deadest spot in the ocean. It seemed to be the obvious place to look for limits of life on Earth, and microbes have, in fact, been found far beneath this oceanic desert. Researchers think that they have been there for at least 100 million years. The previous record for longevity was held by microbes that had survived for 15 million years but this most recent discovery exceeds that tenfold and raises some intriguing questions.
The microbes from the South Pacific Gyre were discovered by geomicrobiologist Yuki Morono of the Japan Agency for Marine-Earth Science and Technology. Morono wanted to know whether organisms are able to survive where there is very little to sustain them. He drilled 5,700 metres below the seabed and extracted clay samples. The samples were found to contain oxygen, enough to allow the microbes to live, although the clay was extremely poor in nutrients. When Morono and his team then introduced nutrients into the samples, they were absorbed by the microbes that were living in the clay. Within a few days, the microbes started to multiply and 557 days later they were still forming thriving communities.
How the organisms survived for so long is a remarkable puzzle that scientists are trying to understand. The microbes are under intense pressure from miles of mud and water above them and do not have food or sunlight. Under inhospitable conditions, some microbes can form spores, or endospores. In this inactive state, they can stay dormant in order to survive extended periods of starvation. But the Pacific microbes had not formed these spores, suggesting two different possibilities.
A microbe can either reproduce by dividing or it can conserve its energy and maintain only its most basic functions. One possibility is that in the unfavourable conditions under the South Pacific floor, the microbes could have been dividing very slowly over centuries. In this case, the microbes in Morono's study may be the descendants of microbes from an even more distant past. However, at the depth where the microbes were found, there is so little nutrition that it seems unlikely that they would have the energy to divide and multiply. In fact, it seems that the most they could do is to self-repair. But if that is the case, and the microbes are not reproducing, they must have been living at the very edge of life for millions of years. This would mean that their metabolism can slow down so much that they can survive with only the tiniest amounts of nutrients. To the researchers, it seemed almost impossible that the microbes would be able to wake up and grow but they did just that.
The study is globally important and, as Yuki Morono stated, it shows that some of the simplest living creatures in the world 'do not actually have the concept of lifespan'. Unfortunately, the research is very difficult to replicate because different areas of the seabed have different compositions and therefore different environments, so is this a unique find? Scientists have collected samples of material from the sub-seabed that are 200 million years old; could they hold even older organisms? This points to another question: at which point under the seafloor does life end and what are the conditions that limit life? These are important questions, not only for life on Earth but also for potential life on other planets. According to Bo Barker Jorgensen from Aarhus University, 'low food and energy seem not to set the ultimate limit for life on Earth'. So, could life exist on places such as Mars or Jupiter's moons? If a planet seems to be uninhabitable, perhaps life may still exist in some form beneath the extra-terrestrial surface.
Questions
Questions 29–31 Multiple Choice (One Answer)
Choose the correct letter, A, B, C or D.
Questions 32–37 True / False / Not Given
Do the following statements agree with the information given in Reading Passage 3?
TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this
Questions 38–40 Summary Completion
Complete the summary below.
Choose ONE WORD ONLY from the passage for each answer.
It seems microorganisms do not have limits to their 38 However, this is hard to confirm because different conditions exist in the seabed and therefore it is hard to 39 the study. According to some scientists, having very little 40 or food is not a barrier to life.
Answers & Explanations Summary
| # | Answer | Evidence | Explanation |
|---|---|---|---|
| Q29 | B | Although microbes are the Earth's simplest organisms, they live in places where it is impossible for more complex life forms to survive | Excerpt/Passage Explanation: The passage says that even though microbes are very simple, they stay alive in areas where larger and more complicated animals and plants are unable to live. Answer Explanation: The answer means that tiny living things called microbes can grow very well in harsh environments where most other animals or plants cannot survive. Reason For Correctness: The correct answer is B because the text explains that microbes are simple organisms that live in locations that are too difficult for bigger, more 'complex' life forms. It mentions they can 'thrive' (which means to flourish or grow well) in extremely hot or cold water where other creatures would die. |
| Q30 | D | It seemed to be the obvious place to look for limits of life on Earth, and microbes have, in fact, been found far beneath this oceanic desert | Excerpt/Passage Explanation: The passage explains that while the South Pacific Gyre is a very empty place, scientists actually found tiny living things called microbes living deep under the ocean floor in that area. Answer Explanation: The answer identifies a statement that is false based on the text. Specifically, it says that living things cannot survive in the South Pacific Gyre, which is incorrect because life was discovered there. Reason For Correctness: The correct answer is D because the second paragraph clearly states that 'microbes have, in fact, been found' in that location. Since microbes are living creatures, their presence proves that it is not 'impossible' for life to exist there. The other choices (A, B, and C) are all supported by the text: it is the point 'furthest from any land', it 'lacks nutrients' (supporting the idea of no means of support), and it is described as an 'obvious place to look for limits of life'. Only choice D is directly contradicted by the evidence of survival mentioned in the passage. |
| Q31 | C | When Morono and his team then introduced nutrients into the samples, they were absorbed by the microbes that were living in the clay. Within a few days, the microbes started to multiply | Excerpt/Passage Explanation: The passage explains that when the scientists gave food to the tiny living things in the clay, the microbes took the food and began to produce more of themselves after just a few days. Answer Explanation: The answer means that Yuki Morono's researchers gave food (nutrients) to the tiny living things (microbes), which caused them to become active and start growing again. Reason For Correctness: The correct answer is correct because the passage describes an experiment where the team added 'nutrients' to the clay samples they had collected. After the microbes 'absorbed' (took in) this food, they 'started to multiply' within a few days. This increase in reproduction is a clear sign that the microbes' level of 'activity' increased because of the nutrients provided by the team. |
| Q32 | TRUE | Researchers think that they have been there for at least 100 million years | Excerpt/Passage Explanation: The passage says that the people who study these things believe the tiny organisms have lived in that place for a minimum of 100 million years. Answer Explanation: The answer is TRUE because the passage states that scientists believe these tiny organisms have survived in that location for 100 million years. Reason For Correctness: The correct answer is TRUE because the text directly supports the statement. In the second paragraph, the author notes that researchers (scientists) believe the microbes found in the South Pacific Gyre have been present for at least 100 million years. This indicates that they 'believe' or 'think' this extreme age is possible for the discovered organisms. |
| Q33 | TRUE | Under inhospitable conditions, some microbes can form spores, or endospores | Excerpt/Passage Explanation: The passage states that when the environment is not easy to live in, some tiny living things (microbes) are able to make special protective cases called spores or endospores. Answer Explanation: The answer means that it is true that microbes create endospores when they are in a environment that is difficult to live in. Reason For Correctness: The correct answer is TRUE because the text says that when conditions are bad for life, some microbes make spores or endospores. In testing, 'inhospitable conditions' and 'physical stress' mean the same thing—times when it is hard to stay alive. The passage explains that microbes use these endospores to stay in a sleeping state called 'dormant' so they can live without food for a long time. |
| Q34 | NOT GIVEN | The microbes are under intense pressure from miles of mud and water above them and do not have food or sunlight | Excerpt/Passage Explanation: The passage says that there is a lot of pressure from the deep water and mud. However, it does not say if this pressure is more than the pressure in other oceans, so we cannot make a comparison. Answer Explanation: The answer is NOT GIVEN because the text does not compare the pressure in the South Pacific Gyre to the pressure in other parts of the ocean. Reason For Correctness: The correct answer is NOT GIVEN because while the passage mentions that these microbes face "intense pressure," it does not provide information about how this pressure compares to what microbes experience in other ocean locations. To answer "True" or "False," the passage would need to specifically state whether this pressure is higher or lower than elsewhere. Since the text only describes the pressure in one specific area (the South Pacific Gyre) and remains silent about the pressure tolerances of microbes in other ocean regions, we cannot confirm the statement. |
| Q35 | FALSE | However, at the depth where the microbes were found, there is so little nutrition that it seems unlikely that they would have the energy to divide and multiply. In fact, it seems that the most they could do is to self-repair | Excerpt/Passage Explanation: The passage explains that because there is almost no food, the microbes cannot grow or make more microbes (divide and multiply). They can only use their tiny amount of energy to fix their own bodies to stay alive. Answer Explanation: The answer is "FALSE," which means the text says something opposite to the statement provided. The statement says the microbes make babies (reproduce) slowly, but the text says they likely do not make babies at all while trapped deep underground. Reason For Correctness: The correct answer is "FALSE" because the passage explains that it is very hard for these microbes to make new ones deep under the sea. While scientists considered the idea of them reproducing slowly, the text says it is "unlikely" because there was not enough food (nutrition) for that to happen. Instead of reproducing, the microbes likely only used their tiny bit of energy to keep themselves alive by fixing their own bodies, which is called "self-repair." |
| Q36 | TRUE | But if that is the case, and the microbes are not reproducing, they must have been living at the very edge of life for millions of years | Excerpt/Passage Explanation: The passage states that if the tiny living things were not making new copies of themselves (reproducing), it means the same individuals have been alive for many millions of years. Answer Explanation: The answer means that if the tiny living things found under the ocean were not making new cells, then the original cells themselves had stayed alive for millions of years. Reason For Correctness: The correct answer is TRUE because the passage explores two ways these tiny organisms (microbes) could have survived. One way is by dividing (splitting to make new cells), while the other is by simply staying alive as the same individual cells. The text clearly states that if they were not reproducing (which is a synonym for not dividing), they must have been living for millions of years. Since the statement matches this specific logic from the passage, it is true. |
| Q37 | FALSE | The samples were found to contain oxygen, enough to allow the microbes to live, although the clay was extremely poor in nutrients | Excerpt/Passage Explanation: The passage explains that when scientists tested the clay from the deep ocean, they found that it had oxygen inside it. This oxygen was sufficient for the microbes to stay alive, even though there was very little food (nutrients) for them. Answer Explanation: The answer is FALSE because the statement claims the microbes lived without oxygen or food, but the passage says they actually had oxygen. Reason For Correctness: The correct answer is FALSE because the passage explicitly mentions that the samples containing the microbes had oxygen. It states that there was enough oxygen available to support the life of these microbes. This information directly conflicts with the part of the question stating they survived 'without oxygen'. Additionally, while nutrients were very low (poor), they were not completely absent, and the presence of oxygen is the main reason why the statement is incorrect. |
| Q38 | lifespan | The study is globally important and, as Yuki Morono stated, it shows that some of the simplest living creatures in the world 'do not actually have the concept of lifespan' | Excerpt/Passage Explanation: The passage explains that, according to a scientist named Yuki Morono, very tiny and simple living things do not have a set length of time that they are allowed to live; they can survive much longer than expected. Answer Explanation: The answer 'lifespan' refers to the amount of time that a person, animal, or plant is expected to live. Reason For Correctness: The correct answer is 'lifespan' because the passage discusses microbes that have survived for at least 100 million years, which is a record-breaking length of time. Yuki Morono, a scientist in the text, concludes that these simple life forms do not seem to follow the normal rules of how long a creature can live. The summary sentence matches this part of the passage where it mentions that these organisms lack a 'concept of lifespan.' |
| Q39 | replicate | Unfortunately, the research is very difficult to replicate because different areas of the seabed have different compositions and therefore different environments, so is this a unique find | Excerpt/Passage Explanation: The passage says that the study is hard to copy or repeat because different places on the ocean floor are made of different things. Answer Explanation: The answer means to do a piece of research or an experiment again in the exact same way to see if you get the same results. Reason For Correctness: The correct answer is 'replicate' because the passage explains that it is very hard for other scientists to repeat Yuki Morono’s experiment. This is because different parts of the ocean floor (the seabed) have different materials and conditions. Since the environments are not the same everywhere, scientists cannot easily do the same study again to check the findings. In the text, the phrase 'difficult to replicate' matches the summary's 'hard to replicate'. |
| Q40 | energy | According to Bo Barker Jorgensen from Aarhus University, 'low food and energy seem not to set the ultimate limit for life on Earth' | Excerpt/Passage Explanation: The passage explains that a scientist thinks having only a small amount of food and power (energy) does not stop life from existing on our planet. Answer Explanation: The answer 'energy' refers to the power or fuel that microorganisms need to stay alive and function. Reason For Correctness: The correct answer is 'energy' because the summary is paraphrasing a specific statement made by a scientist at the end of the text. The passage mentions that according to Bo Barker Jorgensen, 'low food and energy' do not set the 'ultimate limit' for life. In the summary, the word 'barrier' is used as a synonym for 'limit', and 'very little' is used as a synonym for 'low'. Since 'food' is already mentioned in the summary, 'energy' is the missing word from that pair. |