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Populations in Ecosystems 2023 Formative
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- AQA
Past paper questions 2016 to 2023 on populations and ecosystems used in A levels and mock exams
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AQA Biology A-Level - Populations in Ecosystems QP PhysicsAndMathsTutor.comQ1.
Read the following passage.
Lake Malawi in East Africa has more species of fish than any other lake in the
world. Many of these species have evolved from a common ancestor. Lake
Malawi is one of the largest lakes in the world and was formed several million
years ago. Since then, the water level has fluctuated greatly. As a result,
5 what is now a large lake was at one time many smaller, separate lakes.
The country of Malawi has a total area of 118 000 km2. The actual land area is
only 94 080 km2, because approximately one-fifth of the country is Lake
Malawi.
In December 1990, forests covered 41.4% of the actual land area of Malawi.
10 In December 2016, forests covered 26.4% of the actual land area of Malawi.
Deforestation and farming along the shores of Lake Malawi have caused
increased soil erosion and loss of nutrients into the lake. This has resulted in
a decrease in some fish populations. The mark-release-recapture method can
be used to estimate the size of a fish population. However, this method can
15 produce unreliable results in very large lakes.
Use the information in the passage and your own knowledge to answer the
following questions.
(a) Lake Malawi in East Africa has more species of fish than any other lake in
the world (line 1).
Suggest and explain how this speciation may have occurred.
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(4)
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, AQA Biology A-Level - Populations in Ecosystems QP PhysicsAndMathsTutor.com
(b) The percentage of forest cover in Malawi decreased between December
1990 and December 2016 (lines 9–10).
Calculate the mean loss of forest cover in km2 per week during this time
period.
Answer _______________ km2 per week
(2)
(c) Loss of nutrients into Lake Malawi has resulted in a decrease in some fish
populations (lines 12–13).
Explain why.
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(4)
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