Population Viability Analysis - IELTS Reading Answers With Explanations

The IELTS Academic Reading passage, “Population Viability Analysis”, is a text that consists of 12 questions. 

With proper and consistent practice, the IELTS Reading test can be the top-scoring part for IELTS candidates like you! By solving and checking the sample Reading questions from past IELTS test papers, you can find out the ways to approach and answer all of the different question types in the test!

Let us begin by taking the reading test on the passage, Population Viability Analysis, below now!

Question Types Found in the Population Viability Analysis IELTS Reading Passage 

The types of questions found in this IELTS Reading passage are:

• IELTS Reading Yes/No/Not Given
• IELTS Matching features 
• IELTS Sentence Completion
• IELTS Reading Multiple Choice Questions

IELTS Yes/ No/ Not Given 

• The Yes/No/ Not Given type of questions in the IELTS reading test are very common and are similar to the True/False/Not Given type of questions. 
• The test-taker shouldn’t confuse themselves with True/False/Not Given type of questions, as the Yes/No/Not Given type of questions will usually contain the opinions, views or beliefs of the writer or other people who are mentioned in the reading passage.
• The test-taker should write Yes, if the statement agrees with the information in the passage, write No, if the statement disagrees or contradicts the information, and write Not Given, if the statement is not mentioned anywhere in the reading passage. 

IELTS Matching Features 

• The matching features type of questions in the IELTS reading test requires the test-taker to match the respective options to a list of statements. 
• These options are usually in the form of names or features, and are presented in a box. 
• The test-taker can scan for the options in the passage, locate the keyword, and match the features according to the statement. 

IELTS Sentence Completion 

• The sentence completion questions are one of the easiest types of questions, which require the test-taker to complete the sentence using words or numbers from the reading text. 
• The number of words filled in the blank spaces shouldn’t exceed the number of words specified in the instructions. 

IELTS Multiple Choice Question 

• The multiple choice question is one of the trickiest types of questions in the IELTS reading test, which requires the test-takers to select the correct answer out of the 3-4 possible choices. 
• The MCQ-type of questions will be in the form of a question-and-answer type. These answers appear in chronological order according to the passage.

Population Viability Analysis - IELTS Reading Passage 

Part A
To make political decisions about the extent and type of forestry in a region it is important to understand the consequences of those decisions. One tool for assessing the impact of forestry on the ecosystem is population viability analysis (PVA). This is a tool for predicting the probability that a species will become extinct in a particular region over a specific period. It has been successfully used in the United States to provide input into resource exploitation decisions and assist wildlife managers and there is now an enormous potential for using population viability to assist wildlife management in Australia’s forests. A species becomes extinct when the last individual dies. This observation is a useful starting point for any discussion of extinction as it highlights the role of luck and chance in the extinction process. To make a prediction about extinction we need to understand the processes that can contribute to it and these fall into four broad categories which are discussed below. 

Part B
A)  Early attempts to predict population viability were based on demographic uncertainty whether an individual survives from one year to the next will largely be a matter of chance. Some pairs may produce several young in a single year while others may produce none in that same year. Small populations will fluctuate enormously because of the random nature of birth and death and these chance fluctuations can cause species extinctions even if, on average, the population size should increase. Taking only this uncertainty of ability to reproduce into account, extinction is unlikely if the number of individuals in a population is above about 50 and the population is growing. 

B)  Small populations cannot avoid a certain amount of inbreeding. This is particularly true if there is a very small number of one sex. For example, if there are only 20 individuals of a species and only one is a male, all future individuals in the species must be descended from that one male. For most animal species such individuals are less likely to survive and reproduce. Inbreeding increases the chance of extinction. 

C)  Variation within a species is the raw material upon which natural selection acts. Without genetic variability, a species lacks the capacity to evolve and cannot adapt to changes in its environment or to new predators and new diseases. The loss of genetic diversity associated with reductions in population size will contribute to the likelihood of extinction.

D)  Recent research has shown that other factors need to be considered. Australia’s environment fluctuates enormously from year to year. These fluctuations add yet another degree of uncertainty to the survival of many species. Catastrophes such as fire, flood, drought or epidemic may reduce population sizes to a small fraction of their average level. When allowance is made for these two additional elements of uncertainty the population size necessary to be confident of persistence for a few hundred years may increase to several thousand. 

Part C
Besides these processes, we need to bear in mind the distribution of a population. A species that occurs in five isolated places each containing 20 individuals will not have the same probability of extinction as a species with a single population of 100 individuals in a single locality. Where logging occurs (that is, the cutting down of forests for timber) forest-dependent creatures in that area will be forced to leave. Ground-dwelling herbivores may return within a decade. However, arboreal marsupials (that is animals which live in trees) may not recover to pre-logging densities for over a century. As more forests are logged, animal population sizes will be reduced further. Regardless of the theory or model that we choose, a reduction in population size decreases the genetic diversity of a population and increases the probability of extinction because of any or all of the processes listed above. It is, therefore, a scientific fact that increasing the area that is loaded in any region will increase the probability that forest-dependent animals will become extinct. 

Questions 1-4:
Do the following statements agree with the views of the writer in Part A of Reading Passage 1? 

In boxes 1-4 on your answer sheet, write: 

YES            if the statement agrees with the writer
NO              if the statement contradicts the writer
NOT GIVEN   if it is impossible to say what the writer thinks about this 

1.   Scientists are interested in the effect of forestry on native animals.
2.   PVA has been used in Australia for many years.
3.   A species is said to be extinct when only one individual exists.
4.   Extinction is a naturally occurring phenomenon.  

Questions 5-8:
These questions are based on Part B of Reading Passage 1. 

In paragraphs A to D the author describes four processes which may contribute to the extinction of a species.
Match the list of processes (i-vi) to the paragraphs.
Write the appropriate number (i-vi) in boxes 5-8 on your answer sheet. 

There are more processes than paragraphs so you will not use all of them.

5. _________

6. _________

7. _________

8. _________

Questions 9-11:
Based on your reading of Part C, complete the sentences below. 

Use NO MORE THAN THREE WORDS for each answer. 

Write your answers in boxes 9-11 on your answer sheet. 

While the population of a species may be on the increase, there is always a chance that small isolated groups .......... (9) .......... Survival of a species depends on a balance between the size of a population and its .......... (10) ......... The likelihood that animals which live in forests will become extinct is increased when ..........  (11) ........... 

Question 12:
Choose the appropriate letter A-D and write it in box 12 on your answer sheet. 

12.  An alternative heading for the passage could be:
    A.  The protection of native flora and fauna
    B.  Influential factors in assessing survival probability
    C.  An economic rationale for the logging of forests
    D.  Preventive measures for the extinction of a species

Population Viability Analysis IELTS Reading Answers and Explanations

The answers to these questions are given below with their explanations.

1 Answer: Yes 

Question type: Yes/ No/ Not Given 

Answer location: Part A 

Answer explanation: In part A of the passage, the writer states that one tool for ‘assessing the impact of forestry on’ the ‘ecosystem’ (native animals) is population viability analysis (PVA). This is a tool for ‘predicting the probability that a species will become extinct in a particular region’ over a specific period. It has been successfully used in the United States to provide input into resource exploitation decisions and assist wildlife managers. This ‘observation’ (scientific process) is a useful starting point for any discussion of extinction as it highlights the role of luck and chance in the extinction process. Hence, the answer is ‘YES’ as the statement agrees with the writer.

2 Answer: No 

Question type: Yes/ No/ Not Given 

Answer location: Part A

Answer explanation: Part A mentions that one tool for assessing the impact of forestry on the ecosystem is ‘population viability analysis (PVA)’. This is a tool for predicting the probability that a species will become extinct in a particular region over a specific period. It is further added that ‘there is now an enormous potential for using population viability to assist wildlife management in Australia’s forests’. Therefore the tool has not been used yet. Hence, the answer is ‘NO’ as the statement contradicts the writer.

3 Answer: No

Question type: Yes/ No/ Not Given 

Answer location: Part A 

Answer explanation: Part A points out the fact that ‘species becomes extinct’ when the ‘last individual dies’. Hence, the answer is ‘NO’ as the statement contradicts the writer.

4 Answer: Not Given 

Question type: Yes/ No/ Not Given 

Answer location: Part A 

Answer explanation: In part A, it is noted that ‘a species becomes extinct when the last individual dies’. This observation is a useful starting point for any discussion of extinction as it highlights the ‘role of luck and chance in the extinction process’. As there is no mention that extinction is a naturally occurring phenomenon, the answer is ‘NOT GIVEN’.

5 Answer: VI

Question type: Matching Features 

Answer location: Paragraph A, part B 

Answer explanation: In paragraph A of part B, it is given that some pairs of individuals may ‘produce several young in a single year’ while others may ‘produce none in that same year’. Small populations will fluctuate enormously because of the ‘random nature of birth’ (haphazard nature of reproduction) and death and these chance ‘fluctuations’ (random changes) can cause species extinctions. Hence, the answer is VI (The haphazard nature of reproduction).

6 Answer: III

Question type: Matching Features

Answer location: Paragraph B, part B 

Answer explanation: In paragraph B of Part B, it is revealed that small populations cannot avoid a certain amount of inbreeding which leads to ‘very small number of one sex’ (imbalance). For example, if there are ‘only 20 individuals of a species’ and ‘only one is a male’, all future individuals in the species must be descended from that one male. Hence, the answer is III (An imbalance of the sexes).

7 Answer: I

Question type: Matching Features 

Answer location: Paragraph C, part B 

Answer explanation: In paragraph C of part B, it is said that variation within a species is the raw material upon which natural selection acts. ‘Without genetic variability’, a ‘species lacks the capacity to evolve’ and ‘cannot adapt to changes in its environment’ (loss of ability to adapt) or to new predators and new diseases. The loss of genetic diversity will ‘contribute to the likelihood of extinction’. Hence, the answer is I (Loss of ability to adapt).

8 Answer: II

Question type: Matching Features 

Answer location: Paragraph D, part B 

Answer explanation: In paragraph D of part B, it is pointed out that  ‘fluctuations in environment add’ yet another degree of ‘uncertainty to the survival of many species’. ‘Catastrophes’ (natural disasters) such as fire, flood, drought or epidemic ‘may reduce population’ sizes to a small fraction of their average level. Hence, the answer is II (Natural disasters).

9 Answer: will (/may) not survive, or (will (/may/could) become extinct) 

Question type: Sentence Completion 

Answer location: Part C

Answer explanation: In part C, the writer discusses the distribution of a population. It is said that ‘a species that occurs in five isolated places’ each containing ‘20 individuals’ (small group) ‘will not have the same probability of extinction’ (there is a chance that it may survive or it may or may not become extinct) as a species with a ‘single population of 100 individuals in a single locality’ (growing population). Hence, the answer is ‘will(/may) not survive, or, [will (/ may/ could) become extinct]’.

10 Answer: locality, distribution 

Question type: Sentence Completion 

Answer location: Part C

Answer explanation: Part C refers to the fact that besides other factors for extinction of a species, ‘distribution of a population’ has to be kept in mind. ‘A species that occurs in five isolated places each containing 20 individuals’ will not have the same probability of extinction as ‘a species with a single population of 100 individuals in a single locality’. So, there should be a balance between the size of the population and the locality. Hence, the answer is ‘locality/ distribution’.

11 Answer: logging takes place/ logging occurs 

Question type: Sentence completion 

Answer location: Part C 

Answer explanation: In part C, it is brought out that ‘where logging occurs’ (that is, the cutting down of forests for timber) ‘forest-dependent creatures in that area will be forced to leave’. As more forests are logged, ‘animal population sizes will be reduced further’ (which will lead to extinction of species). Hence, the answer is ‘logging takes place/logging occurs’.

12 Answer: B 

Question type: Multiple Choice Question 

Answer location: Part A, Paragraph A (part B), Paragraph B (part B), Paragraph C (part B), paragraph D (part C), Part C 

Answer explanation: In part A, the writer talks about ‘population viability analysis (PVA)’, a tool for assessing the impact of forestry on the ecosystem. This is ‘a tool for predicting the probability that a species will become extinct’ in a particular region over a specific period. In paragraph A of part B, it is said that ‘early attempts to predict population viability were based on demographic uncertainty’ whether an individual survives from one year to the next will largely be a matter of chance. In paragraph B of part B, it is noted that ‘inbreeding increases the chance of extinction’, which is further supported by the fact that the ‘loss of genetic diversity associated with reductions in population size will contribute to the likelihood of extinction’ in paragraph C of part B. In paragraph D of part B, it is added that recent research has shown that other factors like ‘catastrophes such as fire, flood, drought or epidemic may reduce population sizes’ to a small fraction of their average level. Finally, in part C, it is concluded that more factors like ‘distribution of a population’ and ‘logging’ will increase the probability that forest-dependent animals will become extinct. Hence, the answer is ‘B’ (Influential factors in assessing survival probability).

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