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Cambridge International Examinations Cambridge ...4 UCLES 2018 9693/23/M/J/18 2 Coral bleaching, in...
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*9680930396* This document consists of 10 printed pages and 2 blank pages. DC (JM) 162447 © UCLES 2018 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level CANDIDATE NAME CENTRE NUMBER CANDIDATE NUMBER MARINE SCIENCE 9693/23 Paper 2 AS Data-Handling and Free-Response May/June 2018 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Section A Answer both questions in this section. Write your answers in the spaces provided on the Question Paper. Section B Answer both questions in this section. Write your answers in the spaces provided on the Question Paper. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.
Transcript of Cambridge International Examinations Cambridge ...4 UCLES 2018 9693/23/M/J/18 2 Coral bleaching, in...
*9680930396*
This document consists of 10 printed pages and 2 blank pages.
DC (JM) 162447© UCLES 2018 [Turn over
Cambridge International ExaminationsCambridge International Advanced Subsidiary and Advanced Level
CANDIDATENAME
CENTRENUMBER
CANDIDATENUMBER
MARINE SCIENCE 9693/23Paper 2 AS Data-Handling and Free-Response May/June 2018 1 hour 15 minutesCandidates answer on the Question Paper.No Additional Materials are required.
READ THESE INSTRUCTIONS FIRST
Write your Centre number, candidate number and name on all the work you hand in.Write in dark blue or black pen.You may use an HB pencil for any diagrams or graphs.Do not use staples, paper clips, glue or correction fluid.DO NOT WRITE IN ANY BARCODES.
Section AAnswer both questions in this section.Write your answers in the spaces provided on the Question Paper.
Section BAnswer both questions in this section.Write your answers in the spaces provided on the Question Paper.
Electronic calculators may be used.You may lose marks if you do not show your working or if you do not use appropriate units.
At the end of the examination, fasten all your work securely together.The number of marks is given in brackets [ ] at the end of each question or part question.
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Section A
Answer both questions in this section.
1 When a whale dies, its carcass (body) falls to the deep ocean floor. The carcass creates a complex ecosystem, which supports a variety of deep-sea organisms for decades.
At first, scavengers and decomposers feed on the carcass. Later, the community of organisms resembles the community found at a hydrothermal vent.
Only the skeleton of the whale remains, and bacteria feeding on it generate hydrogen sulfide. This is used by chemosynthetic bacteria, which support a food web including many diverse and rare species of mussels, worms and snails.
(a) State the trophic level of the chemosynthetic bacteria. Explain your answer.
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Table 1.1 shows the change in the number of species on a newly fallen whale carcass over time.
Table 1.1
age of whale carcass / months number of specieson the whale carcass
6 15
14 31
24 33
33 38
42 42
57 50
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(b) On the grid, plot a graph of the data in Table 1.1. Join the points on your graph with ruled straight lines.
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(c) Describe the relationship between the age of whale carcass and the number of species present.
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[Total: 9]
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2 Coral bleaching, in which coral polyps expel their zooxanthellae, can be caused by increased sea water temperature.
(a) State the type of interrelationship between coral and zooxanthellae.
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Some marine biologists suggested the hypothesis that coral reef communities do not recover from coral bleaching.
Fig. 2.1 is a graph of the predicted changes following a severe coral bleaching event based on this hypothesis.
0–1.0
–0.5
0.0
0.5
1.0
1 2 3 4 5 6 7 8 9 10time after severe
coral bleaching event / years
proportionalchange
severe coralbleaching event
algae cover
coral cover
number of fish species
Fig. 2.1
(b) (i) Describe how the coral reef communities ten years after a bleaching event are predicted to differ from the communities before the event occurred.
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(ii) Suggest how the predicted changes in algae cover may result in a reduction in coral cover.
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(c) In 1998, a reef in Western Australia suffered a severe coral bleaching event.
Fig. 2.2 shows the results of a study of the changes in percentage coral cover and percentage algae cover before and after this event. It also shows the changes in the density of herbivorous fish.
1996 1998 2000 2002 2004 2006 2008 20100
25
50
75
100
year
75
50
25
0
percentagecover
fish density/ arbitrary
units
herbivorous fish
algae cover
coral cover
severe coralbleaching event
Fig. 2.2
(i) Suggest how percentage coral cover may be measured on a coral reef.
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(ii) Explain why the hypothesis that coral reef communities do not recover from a bleaching event is not supported by the results shown in Fig. 2.2.
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(iii) Use information from Fig. 2.2 to suggest a reason for the changes in density of herbivorous fish.
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[Total: 11]
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Section B
Answer both questions in this section.
3 (a) Describe how a tropical cyclone develops.
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(b) Explain the meaning of the terms ecosystem and biodiversity.
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(c) Outline how mangroves protect tropical coastlines.
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[Total: 15]
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4 The Humboldt Current off the coasts of Chile and Peru causes upwelling. This supports huge shoals of the Peruvian anchoveta, which provide the greatest catches of any fish species.
(a) Explain how upwelling supports large numbers of fish.
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(b) Discuss the advantages of shoaling in fish such as the Peruvian anchoveta.
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(c) Describe the causes of El Niño events. Explain how such an event may result in the collapse of the Peruvian anchoveta population.
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[Total: 15]
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