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Population Viability Analysis: Reading Answers

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Cambridge 1 Academic Test 4 – Passage 03: Population viability analysis reading answers location, explanation and pdf summary. This reading paragraph has been taken from our huge collection of Academic & General Training (GT) Reading practice test PDF’s.

IELTS reading module focuses on evaluating a candidate’s comprehension skills and ability to understand English. This is done by testing the reading proficiency through questions based on different structures and paragraphs (500-950 words each). There are 40 questions in total and hence it becomes extremely important to practice each and every question structure before actually sitting for the exam.

This reading passage mainly consists of following types of questions:

  • Multiple choice questions
  • Match the following
  • Fill in the blanks

We are going to read about the role of population analysis in nature preservation. You must read the passage carefully and try to answer all questions correctly. 

Population viability analysis

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 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

Beside 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 28-31

Do the following statements agree with the views of the writer in Part A of Reading Passage 3? In boxes 28-31 on your answer sheet write:

Population Viability Analysis: Reading Answers

28. Scientists are interested in the effect of forestry on native animals.

29. PVA has been used in Australia for many years.

30. A species is said to be extinct when only one individual exists.

31. Extinction is a naturally occurring phenomenon.

Questions 32-35

These questions are based on Part B of Reading Passage 3.

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 32-35 on your population viability analysis reading answers sheet.

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

Population Viability Analysis Reading Answers

Questions 36-38

Based on your reading of Part C, complete the sentences below with words taken from the passage.

Use NO MORE THAN THREE WORDS for each answer. Write your answers in boxes 36-38 on your answer sheet.

While the population of a species may be on the increase, there is always a chance that small isolated groups … (36) …

Survival of a species depends on a balance between the size of a population and its … (37) …

The likelihood that animals which live in forests will become extinct is increased when … (38) …

Question 39

Choose the appropriate letter A-D and write it in box 39 on your answer sheet.

39. 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


Check out your Population viability analysis reading answers below with locations and explanations given in the text.

QuestionsTaskSkills tested
28-31Yes, No, Not Given• skimming for detailed information
• understanding gist and paraphrase
• identifying opinion
32-35Matching (processes to paragraphs)• detailed reading
• identifying main and supporting points
• understanding gist and paraphrase
36-38Sentence completion• skimming for information
• understanding paraphrase
39Global multiple choice• understanding the overall theme of the passage

Questions 32-35

(Suggested approach)

• Read the task rubric carefully. Note that these questions are based on Part B of the reading passage. You will have to decide which paragraphs in this part cover which processes.

• Note that there are two extra processes which are not described. The extra processes will be close to the correct answers but not correct. Read the text carefully so that you do not fall into any traps.

• Read through the list of processes to familiarise yourself with them.

• Read paragraph A carefully, noting any sections that relate to the processes described in i – vi.

• Paragraph A states that survival of a species is largely a “matter of chance” and that not all animals produce young at the same rate. The meaning of this paragraph can therefore be glossed as “the haphazard nature of reproduction” and vi is the correct answer to question 32.

• Repeat this procedure with questions 33-35.

QuestionAnswerFocus of paragraph
32viThe fluctuation in reproduction rates.
33iiiThe problems of having a small or unequal number of one sex.
34iThe effect on survival of an animal’s ability to adapt to changes and therefore avoid extinction.
35iiThe fluctuating environment in Australia, e.g. fire, flood and drought.
36will/may not survive//will/may/could become extinct
38logging takes place/occurs
Have any doubts??? Discuss in the comments ...

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