Cambridge A Level Marine Science 9693 — 2021 Oct/Nov Paper 2 · Variant 0

1 The distribution of seven different species of mangrove tree, A to G, along several Australian estuaries was investigated. In each estuary, locations were classified as upper, middle and lower. This is shown in Fig. 1.1. upper middle X lower ocean Fig. 1.1 The intertidal zones on the shore of each estuary were classified as high, medium and low. This is shown in Fig. 1.2. mean high tide high intertidal zone X medium intertidal zone low intertidal zone mean low tide Fig. 1.2 The researchers counted the number of each species of mangrove tree in the three locations in each estuary. They calculated the mean percentage of each species in each location. They recorded the presence or absence of each species in each intertidal zone. Their results are shown in Table 1.1. Table 1.1 mean percentage of each species at presence of each species at each location in the estuary each intertidal zone species upper middle lower high medium low A 82 14 4   B 70 26 4   C 25 39 36   D 35 46 19  E 30 57 13   F 3 43 54  G 4 4 92  (a) Use Fig. 1.1, Fig. 1.2 and Table 1.1 to state and explain which species, A to G: (i) is most tolerant of the widest range of salinities ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) is most tolerant of long periods exposed to air ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (iii) is most likely to be found at position X, which is shown in Fig. 1.1 and Fig. 1.2. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (b) (i) Explain why the scientists collected data from more than one estuary. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] (ii) Suggest one other variable that may affect the distribution of mangrove tree species, other than salinity or time exposed to air. ..................................................................................................................................... [1] [Total: 9]

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2 An investigation was carried out to compare the effect of cleaner fish on a species of damselfish. The cleaner fish remove external parasites from the damselfish at cleaning stations. Damselfish live in shallow-water fringing reefs. They defend their exclusive territories from other damselfish. A number of damselfish were observed at sites around each of six different islands, H to M. At each island site half of the damselfish had a cleaning station in their territory. The other half of the damselfish had no cleaning station in their territory. This is shown for one island in Fig. 2.1. island Key individual damselfish territories cleaning stations Fig. 2.1 The damselfish were collected for examination and the number of external parasites on each damselfish was counted. The mean number of external parasites per damselfish was calculated. Fig. 2.2 shows the results of the investigation. 4 3 Key (10)(10) = cleaning mean number (8)(8) station in the territoryof external 2 parasites = per no cleaning damselfish station in the (6)(6) territory 1 (10)(10) (11)(11) (13)(13) (number) = (9)(9) (8)(8) number of (10)(10) (9)(9) damselfish collected 0 H I J K L M island Fig. 2.2 (a) The data for island K are shown in Table 2.1. Table 2.1 total number total number of mean number of of damselfish external parasites external parasites collected found per damselfish damselfish with 12 8 cleaning stations ................................. damselfish without 13 22 cleaning stations ................................. (i) Calculate the mean number of external parasites per damselfish for damselfish with cleaning stations and damselfish without cleaning stations. Add this information to Table 2.1. [1] (ii) Use your calculated numbers from (i) to complete the graph for island K in Fig. 2.2. [2] (b) Use Fig. 2.2 to calculate the percentage difference between the mean number of external parasites on damselfish that do not have a cleaning station and those that do, for island M. Show your working. .......................................................% [3] (c) Discuss the extent to which these data support the theory that cleaner fish reduce the number of external parasites on damselfish. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [3] (d) Suggest two other variables that may affect external parasite numbers on damselfish. 1 ................................................................................................................................................ 2 ................................................................................................................................................ [2] [Total: 11]

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3 Ocean currents can distribute nutrients and organisms around the globe. (a) Discuss the factors that cause both surface and deep oceanic currents to form. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [7] (b) Describe the cycling of calcium within the marine environment. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [8] [Total: 15]

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4 (a) Coral polyps have a symbiotic relationship with zooxanthellae. Name and describe this relationship. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [4] (b) Productivity is the rate of production of biomass in an ecosystem. Explain why coral reefs typically have a high productivity. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [5] (c) Many fish living on coral reefs are shoaling fish. Explain why shoaling is a successful strategy for fish. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [6] [Total: 15]

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