Population Viability Analysis Reading Answers
The Academic passage ‘Population Viability Analysis’ is a reading passage that appeared in an IELTS Test. Read the passage below and answer questions 1-12. Beyond the questions, you will find the answers along with the location of the answers in the passage and the keywords that help you find out the answers.
Population Viability Analysis
The answers to these questions are given below with their explanations.
|1||YES||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||NO||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||NO||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||NOT GIVEN||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||VI||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||III||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||I||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||II||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||will(/may) not survive, or, [will (/ may/ could) become extinct]||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||locality/ distribution||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||logging takes place/ logging occurs||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||B||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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