CAMBRIDGE IELTS 1
PRACTICE TEST 4
READING
READING PASSAGE 3
You should spend about 20 minutes on Questions
28-39 which are based on Reading Passage 3 below
Population
viability analysis
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Part A
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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.
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Part B
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Part C
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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.
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Questions 14-19
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
YES
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if the statement agrees with the
writer
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NO
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if the statement contradicts the
writer
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NOT GIVEN
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if it is impossible to say what
the writer thinks about this
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Example
A link exist
between the consequences of decisions and the decision making process itself.
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Answer
YES
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28
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Scientists
are interested in the effect of forestry on native animals.
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29
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PVA has been
used in Australia for many years.
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30
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A species is
said to be extinct when only one individual exists.
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31
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Extinction
is a naturally occurring phenomenon.
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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 answer sheet.
NB There are more
processes than paragraphs so you will not use all of them.
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Processes
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32
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Paragraph A
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i
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Loss of ability to adapt
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33
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Paragraph
B
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ii
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Natural disasters
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34
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Paragraph
C
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iii
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An imblance of the sexes
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35
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Paragraph
D
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iv
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Human disasters
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v
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Evolution
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vi
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The haphazard nature of reproduction
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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) ...
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Question 39
Choose the appropriate letter A-D and
write it in box 39 on your answer sheet.
39
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An alternative heading for the passage
could be:
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A
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The protection of native flora and
fauna
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B
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Influential factors in assessing
survival probability
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C
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An economic rationale for the logging
of forests
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D
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Preventive measures for the extinction
of a species
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ANSWER KEY
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