Cambridge A Level Marine Science 9693 — 2015 Oct/Nov Paper 2 · Variant 1

This document consists of 11 printed pages and 1 blank page. DC (KN/JG) 95773/4 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 4 6 9 9 9 6 5 3 9 0 * MARINE SCIENCE 9693/02 Paper 2 AS Data-Handling and Free-Response October/November 2015 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.

2 9693/02/O/N/15 © UCLES 2015 Section A Answer both questions in this section. 1 Limpets (Patella vulgata) and periwinkles (Littorina littorea) are two species of mollusc found on rocky shores. Fig. 1.1 shows limpets, which feed on producers growing on the surface of rocks. Fig. 1.1 (a) State the trophic level occupied by limpets. Give an explanation for your answer. … … … …[2]

3 9693/02/O/N/15 © UCLES 2015 [Turn over (b) An investigation was carried out into the distribution of limpets and periwinkles on a rocky shore. A quadrat measuring 0.5 m × 0.5 m was used. The numbers of these molluscs per quadrat were counted every two metres from the low water mark to the top of the shore. The results are shown in Table 1.1. Table 1.1 distance from low water mark / m number of limpets per quadrat number of periwinkles per quadrat 0 0 0 2 0 4 4 0 3 6 0 2 8 0 3 10 0 2 12 0 3 14 3 2 16 6 1 18 10 0 20 13 0 22 2 0 24 1 0 26 0 0 28 0 0 30 0 0 (i) Using the data in Table 1.1, compare the distribution of these two species of mollusc. … … … … … … …[3]

4 9693/02/O/N/15 © UCLES 2015 (ii) Suggest three environmental factors that could influence the distribution of these molluscs on a rocky shore. 1 … 2 … 3 …[3] (c) In a second investigation, a student measured the heights of the shells of 12 limpets on an exposed rocky shore. They then measured the heights of 12 limpets on a sheltered rocky shore. Their results are shown in Table 1.2. Table 1.2 height of limpet shell / mm exposed shore sheltered shore 19 15 33 19 23 17 16 18 18 12 20 18 19 23 22 18 27 15 26 18 22 10 27 14 mean = mean = (i) Complete Table 1.2 by calculating the mean height of the shells on the exposed shore and on the sheltered shore. [2] (ii) Formulate a hypothesis based on the data in Table 1.2. … …[1] [Total: 11]

5 9693/02/O/N/15 © UCLES 2015 [Turn over Question 2 starts on page 6

6 9693/02/O/N/15 © UCLES 2015 2 The concentration of phosphorus was measured in samples of sea water from six different depths, in an area of upwelling in the Atlantic Ocean. The phosphorus was in the form of phosphate ions. Table 2.1 shows the results. Table 2.1 depth / m concentration of phosphorus / μ mol dm–3 250 3.0 500 2.2 1000 1.6 1500 1.4 2000 1.2 2500 1.2 (a) Plot a graph of the data in Table 2.1. Join the points on your graph with straight lines. [4]

7 9693/02/O/N/15 © UCLES 2015 [Turn over (b) Describe the relationship between depth and the concentration of phosphorus. … … … … … … …[3] (c) Suggest what effect this upwelling would have on the productivity of producers in the surface water. Give an explanation for your answer. … … … …[2] [Total: 9]

8 9693/02/O/N/15 © UCLES 2015 Section B Answer both questions in this section. 3 (a) Outline how tectonic processes give rise to the formation of hydrothermal vents. … … … … … … … … … …[4] (b) Explain why hydrothermal vents have a relatively low biodiversity. … … … … … … … … … … … …[5]

9 9693/02/O/N/15 © UCLES 2015 [Turn over (c) Explain how energy is made available to food chains at hydrothermal vents. … … … … … … … … … … … … … … … …[6] [Total: 15]

10 9693/02/O/N/15 © UCLES 2015 4 (a) Explain the meaning of each of the following terms used in ecology. (i) habitat … …[1] (ii) community … … … …[2] (b) Striped bass are predators of other species of fish, including herring. Explain how the populations of striped bass and herring may be interrelated. … … … … … … … … … …[4]

11 9693/02/O/N/15 © UCLES 2015 (c) Many species of fish form large shoals. Discuss the advantages of shoaling to fish such as tuna. … … … … … … … … … … … … … … … … … … … … … …[8] [Total: 15]

12 9693/02/O/N/15 © UCLES 2015 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. BLANK PAGE

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the October/November 2015 series 9693 MARINE SCIENCE 9693/02 Paper 2 (AS Data Handling and Free-Response), maximum raw mark 50 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 Question Expected answers Additional guidance Marks 1 (a) second (trophic level) ; limpets are herbivores / feed on producers / are primary consumers ; [2] (b) (i) any 3 of: periwinkles found on lower shore, limpets found on middle of shore / AW ; periwinkles more widely distributed / found in 8 quadrants, limpets found in 6 quadrants ; limpets distributed over 10 m, periwinkles over 14 m ; neither species found at 0 m / at top of shore / 26 to 30 m ; [3]

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 (ii) any 3 of: immersion time / exposure / AW ; wave action ; temperature ; availability of food ; predators ; competition ; [3] (c) (i) mean on exposed shore = 22.7 ; mean on sheltered shore = 16.4 ; [2] (ii) limpets have flatter shells on a sheltered shore / converse / AW ; [1] [Total: 11]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 Question Expected answers Additional guidance Marks 2 (a) suitable linear scale ; both axes labelled with units + correct orientation ; all points plotted correctly ; points joined accurately with ruled lines + no extrapolation ; sample graph: [4] (b) as depth increases, the concentration of phosphorus decreases / converse ; reference to non-linear ; credit a quantitative reference, e.g. overall change in phosphorus of 1.8 µmol dm -3 ; [3] (c) reference to increased productivity ; producers need phosphorus for DNA ; Accept other P-containing organic substances, e.g. ATP, phospholipids, etc. [2] [Total: 9] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 500 1000 1500 2000 2500 depth / m concentration of phosphorus / micromoles per dm 3

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 Question Expected answers Additional guidance Marks 3 (a) any 4 of: reference to tectonic plates moving apart ; or together ; subduction ; leaving fissures / AW ; sea water moves in ; heated by (hot) magma ; hot water (and dissolved minerals) re-emerges / AW ; [4] (b) reference to hydrothermal vents as extreme environments ; credit two conditions associated with hydrothermal vents, e.g. high temperature, acidity, high pressure, no light ; ; few organisms adapted to survive ; credit an example of an organism associated with hydrothermal vent, e.g. tube worms ; [5]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 (c) any 6 of: reference to bacteria ; chemosynthesis ; oxidise inorganic substances, e.g. H2S ; fix carbon dioxide ; to form organic substances / named example ; for higher other organisms / higher trophic levels ; credit reference to chemosynthetic bacteria forming a symbiotic relationship with tube worms / clams ; [6] [Total: 15]

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 Question Expected answers Additional guidance Marks 4 (a) (i) the place where an organism lives ; [1] (ii) organisms of different species ; living in the same habitat / AW ; [2] (b) any 4 of: as numbers of herring increases ; more food available to striped bass ; (therefore) striped bass numbers increase ; reference to cyclic changes / graph showing changes ; may be no relationship if striped bass have alternative food source / if striped bass are not a major predator of herring ; Accept converse points [4]

Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9693 02 © Cambridge International Examinations 2015 (c) increased hydrodynamic efficiency / reduced drag ; increases swimming speed ; saves energy ; increases foraging efficiency / AW ; protection from predators ; shoal includes males and females ; proximity of mates ; increases chances of fertilisation ; [8] [Total: 15]