The mangrove forest — Paper 2 · A Level Marine Science 9693

3 (a) Describe how a tropical cyclone develops. … … … … … … … … … … [5] (b) Explain the meaning of the terms ecosystem and biodiversity. … … … … … … … … … … [5] (c) Outline how mangroves protect tropical coastlines. … … … … … … … … … … [5] [Total: 15]

15 marks

Mark scheme: 3(a) any five of sea surface (temperature) at least 26.5 °C / 80 °F ; low (air) pressure / low (air) pressure system ; minimum sea depth of 50 m ; idea of, sufficiently far from equator to provide spin or twist / Coriolis effect ; idea of, rotating winds OR winds from different directions ; evaporation ; (gives rise to warm) moist air ; (air) rises and cools OR rises and draws in/up cooler air ; condensation ; release of latent heat ; idea of, this energy perpetuates cyclone further ; low wind-shear ; 5 A sea at least 26.5 °C A warm water at surface warm sea water unqualified is insufficient A circling / spiralling I strong wind unqualified Question Answer Marks Guidance 3(b) any five of ecosystem interaction between ; (community of) living organisms AND non-living components / biotic AND abiotic factors ; linked through, nutrient cycles ; (and) movement of, energy / nutrients, through, food chains / food webs ; biodiversity ref. number of species ; idea of, ref. evenness / relative abundance of each / AW ; (in an) ecosystem / habitat ; 5 3(c) any five of idea of, mangroves live in intertidal regions / delta regions / salt tolerant ; idea of, interlocking / thick / complex, root (system) ; idea of, protect from wave (action) ; energy dissipation ; reduction in, current / flow, speed ; reduce erosion ; increase sedimentation / fine sediment accumulates ; AVP ; 5 e.g. ref. extreme events

This question in 9693/22 May/June 2018

3 (a) Describe how a tropical cyclone develops. … … … … … … … … … … [5] (b) Explain the meaning of the terms ecosystem and biodiversity. … … … … … … … … … … [5] (c) Outline how mangroves protect tropical coastlines. … … … … … … … … … … [5] [Total: 15]

15 marks

Mark scheme: 3(a) any five of sea surface (temperature) at least 26.5 °C / 80 °F ; low (air) pressure / low (air) pressure system ; minimum sea depth of 50 m ; idea of, sufficiently far from equator to provide spin or twist / Coriolis effect ; idea of, rotating winds OR winds from different directions ; evaporation ; (gives rise to warm) moist air ; (air) rises and cools OR rises and draws in/up cooler air ; condensation ; release of latent heat ; idea of, this energy perpetuates cyclone further ; low wind-shear ; 5 A sea at least 26.5 °C A warm water at surface warm sea water unqualified is insufficient A circling / spiralling I strong wind unqualified Question Answer Marks Guidance 3(b) any five of ecosystem interaction between ; (community of) living organisms AND non-living components / biotic AND abiotic factors ; linked through, nutrient cycles ; (and) movement of, energy / nutrients, through, food chains / food webs ; biodiversity ref. number of species ; idea of, ref. evenness / relative abundance of each / AW ; (in an) ecosystem / habitat ; 5 3(c) any five of idea of, mangroves live in intertidal regions / delta regions / salt tolerant ; idea of, interlocking / thick / complex, root (system) ; idea of, protect from wave (action) ; energy dissipation ; reduction in, current / flow, speed ; reduce erosion ; increase sedimentation / fine sediment accumulates ; AVP ; 5 e.g. ref. extreme events

This question in 9693/23 May/June 2018

3 (a) (i) Outline the environmental factors of shorelines that are required for the development of mangrove forests. … … … … … … … … [4] (ii) Explain how the tidal cycle would affect the salinity in a mangrove forest in an estuary over the period of a single day. … … … … … … … … [4] (iii) Suggest two impacts of removing mangrove forests from a shoreline. 1 … … 2 … … [2] (b) Coral reefs are rarely found near river estuaries or deltas. Explain the reasons for this. … … … … … … … … … … [5] [Total: 15]

15 marks

This question in 9693/20 Oct/Nov 2019

1 Fig. 1.1 shows mangroves growing in a tropical delta ecosystem. Fig. 1.1 Samples of surface water were taken from the same location in this delta at regular intervals each day over a seven day period. The salinity levels in each sample were tested and recorded in parts per thousand (‰). Fig. 1.2 shows the results. 40 35 30 salinity / ‰ 25 20 15 midnight midnight midnight midnight midnight midnight midnight 00:00 00:00 00:00 00:00 00:00 00:00 00:00 1 Nov 2 Nov 3 Nov 4 Nov 5 Nov 6 Nov 7 Nov day Fig. 1.2 (a) (i) Use Fig. 1.2 to state the maximum and minimum salinity on the 5 November. maximum … ‰ minimum … ‰ [1] (ii) Describe the patterns shown by the data in Fig. 1.2. … … … … … … [3] (iii) Explain reasons for the patterns shown in Fig. 1.2. … … … … … … [3] (b) Suggest why this ecosystem has a very specific community that can survive there. … … … … … … [3] [Total: 10]

10 marks

Mark scheme: 1(a)(i) Maximum 36.0 and minimum 25.5 ; 1 1(a)(ii) any 3 from: salinity rises and falls twice per 24hr period ; overall salinity levels rising over the seven day period ; (significant) peak on 7th Nov ; (significant) trough on 1st Nov ; peaks/troughs gradually becoming later each day ; idea of, daily range changes ; 3 1(a)(iii) any 3 from: tide rises and falls twice per 24hr period ; tidal cycle causes change in height of tide ; higher tide causes higher salinity ORA ; variations in run-off will affect dilution ; impact of varying precipitation on run-off ; tidal cycle is just over 12 hours so peaks / troughs shift slightly to right ; credit named example of factor affecting tidal height e.g. wind / air pressure ; 3 1(b) any 3 from ; idea of, must have adaptation / features allowing them to survive in this environment ; (difficulty of surviving in) changing salinity ; (difficulty of surviving in) changing oxygen levels ; temperature fluctuations ; potential for dessication due to salt / water fluctuations ; 3

This question in 9693/22 May/June 2020

1 Fig. 1.1 shows mangroves growing in a tropical delta ecosystem. Fig. 1.1 Samples of surface water were taken from the same location in this delta at regular intervals each day over a seven day period. The salinity levels in each sample were tested and recorded in parts per thousand (‰). Fig. 1.2 shows the results. 40 35 30 salinity / ‰ 25 20 15 midnight midnight midnight midnight midnight midnight midnight 00:00 00:00 00:00 00:00 00:00 00:00 00:00 1 Nov 2 Nov 3 Nov 4 Nov 5 Nov 6 Nov 7 Nov day Fig. 1.2 (a) (i) Use Fig. 1.2 to state the maximum and minimum salinity on the 5 November. maximum … ‰ minimum … ‰ [1] (ii) Describe the patterns shown by the data in Fig. 1.2. … … … … … … [3] (iii) Explain reasons for the patterns shown in Fig. 1.2. … … … … … … [3] (b) Suggest why this ecosystem has a very specific community that can survive there. … … … … … … [3] [Total: 10]

10 marks

Mark scheme: Question Answer Marks 1(a)(i) Maximum 36.0 and minimum 25.5 ; 1 1(a)(ii) any 3 from: 3 salinity rises and falls twice per 24hr period ; overall salinity levels rising over the seven day period ; (significant) peak on 7th Nov ; (significant) trough on 1st Nov ; peaks/troughs gradually becoming later each day ; idea of, daily range changes ; 1(a)(iii) any 3 from: 3 tide rises and falls twice per 24hr period ; tidal cycle causes change in height of tide ; higher tide causes higher salinity ORA ; variations in run-off will affect dilution ; impact of varying precipitation on run-off ; tidal cycle is just over 12 hours so peaks / troughs shift slightly to right ; credit named example of factor affecting tidal height e.g. wind / air pressure ; 1(b) any 3 from ; 3 idea of, must have adaptation / features allowing them to survive in this environment ; (difficulty of surviving in) changing salinity ; (difficulty of surviving in) changing oxygen levels ; temperature fluctuations ; potential for dessication due to salt / water fluctuations ;

This question in 9693/23 May/June 2020

4 Mangrove ecosystems are a feature of tropical river deltas. (a) Describe the importance of mangroves for the morphology of deltas. … … … … … … … … [4] (b) After long periods of rain, the volume of water passing through a delta increases. (i) Suggest impacts of this increase on the environmental conditions for organisms living in the delta. … … … … … … … … … … [5] (ii) Suggest why an increased volume of river water entering the ocean may decrease coral reef productivity. … … … … … … … … … … … … [6] [Total: 15]

15 marks

Mark scheme: 4(a) any 4 of: extensive / prop roots / large / many / system of, roots of mangroves ; (roots / mangrove) help reduce water speed / current ; (roots / mangrove) allow for (increased) sedimentation / deposition ; (roots / mangrove) ref. to accumulation of, silt / sand / fine particles ; (roots / mangrove) ref. to reduction of erosion ; 4(b)(i) any 5 of: 1 increased erosion / movement of sediments ; 2 causing changes in morphology of delta ; 3 increased turbidity ; 4 (idea of) reduction in light (for photosynthesis) ; 5 increased nutrient availability / influx of nutrients ; 6 may increase productivity ; 7 decreased salinity ; 8 due to greater influx of freshwater ; 9 increased, depth / height of water / flooding ; 10 reduced opportunity for feeding by littoral organisms ; 11 increased current flow ; 12 so reduced ability of organisms to attach / organisms washed away ; 13 water temperature, increase / decrease ; 14 correct change to oxygen content of water ; 15 AVP ; 5 Question Answer Marks 4(b)(ii) any 6 of: 1 increased (volume) of nutrients / fertilisers in water ; 2 may cause algal bloom / eutrophication ; 3 increased turbidity of water ; 4 decreased, penetration of light (intensity) ; 5 temperature will change ; 6 dissolved carbon dioxide content of water is changed ; 7 will affect (the rate of) photosynthesis ; 8 (temperature / eutrophication) correct effect on dissolved oxygen ; 9 reduced production of organic, material / nutrients ; 10 (by) zooxanthellae ; 11 sediments in water ; 12 sediments, block mouths of coral polyps / prevent coral attachment / cause abrasion ; 13 ref. uses to negative impact of pesticides on corals 14 decreased salinity ; 6

This question in 9693/21 May/June 2021

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]

9 marks

This question in 9693/20 Oct/Nov 2021

3 Mangrove forests are globally threatened ecosystems. (a) Describe one adaptation of the red mangrove tree (Rhizophora mangle) for its environment. … … [1] (b) Mangrove forests can be regenerated by growing mangrove seedlings in controlled conditions and planting them into their native forest ecosystems. Scientists investigated the survival of three species of mangrove seedlings (species X, Y and Z) in different salinities of sea water. 50 seedlings of each species were grown in three different salinities: • low salinity (4 ppt) • moderate salinity (16 ppt) • high salinity (34 ppt). The seedlings were kept at these salinities for 30 weeks. The percentage of seedlings surviving was recorded every two weeks. (i) Suggest how the scientists created the different salinity treatments. … … … … [2] (ii) Describe two ways in which this investigation could be improved. 1 … … 2 … … [2] (c) Fig. 3.1 shows the results from this investigation. Key low salinity moderate salinity high salinity 100 80 percentage 60 of seedlings surviving 40 20 species X 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 time / weeks 100 80 percentage 60 of seedlings surviving 40 20 species Y 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 time / weeks 100 80 percentage 60 of seedlings surviving 40 20 species Z 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 time / weeks Fig. 3.1 (i) Describe how the percentage of seedlings surviving in each salinity was calculated. … … [1] (ii) Calculate how many seedlings of species Z survived the first 10 weeks of the investigation in the highest salinity. Show your working. … [2] (d) Fig. 3.2 shows three locations, A, B and C, in a delta. shoreline C A B river water flow delta channels Fig. 3.2 Use the information in Fig. 3.1 and Fig. 3.2 to suggest which species is best adapted to survive at location A. Explain your answer. … … … … … … [3] (e) At the delta, seedlings will be exposed to changes in the tidal cycle. Suggest why the tidal cycle will cause variations in the salinity of the water at location B. … … … … … … [3] (f) The conservation of mangrove ecosystems is important for human populations. State two benefits. 1 … … 2 … … [2] [Total: 16]

16 marks

Mark scheme: 3(a) any 1 of: prop roots ; salt exclusion by roots / roots help filter salt water ; viviparous reproduction / propagules ; 1 3(b)(i) either: known mass of, sodium chloride / salt ; dissolved in, known / stated, volume / mass, of water ; or: use, (stock) solution / sea water, of known concentration / 34 ppt ; and dilute known volume with known volume of water ; or: add salt to, distilled / fresh, water OR (dilute) seawater with distilled / fresh, water + using a, salinometer / refractometer ; until it reaches the correct salinity ; 2 3(b)(ii) any 2 of: (investigate for) longer than 30 weeks ; (investigate) more (than 3) species ; (investigate) a greater range of salinities ; more seedlings ; 2 3(c)(i) surviving number / 50,  100 ; 1 Question Answer Marks 3(c)(ii) 48  100  50 OR 48  is 48 in 100 so 24 in 50 OR 24 / 50  0.48 OR 48  2 ; 24 ; 2 3(d) species X + highest survival rate in most saline water ; Site A highest salinity (closest to sea / shoreline) ; Site A will experience, least mixing with fresh water / fresh water spread out over a wider area / more time mixed with incoming sea water AW ; 3 3(e) (idea of) high tide increasing salinity / water becomes more saline at high tide / as tide comes in more salty water will be at B / as tide goes out more fresh water will be at B / ORA ; (idea of) increased (proportion of) sea water to freshwater / ORA ; (idea of) spring tides cause greater increase in salinity (at high water) / ORA for neap tides ; 3 3(f) any 2 of: tourism ; food sources / nursery grounds for fish / fisheries / provide nutrients ; (source of) timber ; coastal protection / flooding / reduce wave energy / prevent erosion ; (source of) fuel ; (source of) (antifungal) drug / medicines / medical use ; 2

This question in 9693/21 May/June 2023

1 Mangrove forests are important ecosystems. (a) Explain the term ecosystem. … … … … [2] (b) Fig. 1.1 shows the area of mangrove forest in ten countries and the areas of mangrove forest that are protected and unprotected. Key protected mangrove forest unprotected mangrove forest 30 000 25 000 20 000 area of mangrove 15 000 forest / km2 10 000 5000 0 IndonesiaBrazilAustraliaMexicoNigeriaMalaysiaMyanmar GuineaBangladeshCuba New Papua countries Fig. 1.1 (i) State the name of the country which protects the greatest percentage of its mangrove forest. … [1] (ii) Calculate the percentage of mangrove forest in Mexico that is protected. Show your working. … % [2] (iii) State two major threats to mangrove forests. 1 … 2 … [2] (c) Some species of macroalgae grow attached to the roots of mangrove trees. Scientists planned an investigation to compare the rate of photosynthesis at different light intensities in two of these species of macroalgae. (i) State the word equation for photosynthesis. … [1] Fig. 1.2 shows their experimental set-up. This closed system is used to fully contain a standardised volume of water which is circulated. An oxygen sensor recorded oxygen concentration in the water. The whole apparatus was submerged into a much larger tank of sea water for the investigation. circulation pump sealed plastic dome macroalgae grid sealed plastic base dissolved oxygen sensor Fig. 1.2 (ii) Identify the dependent variable. … [1] (iii) Suggest two variables that should be standardised in this investigation. 1 … 2 … [1] (iv) Suggest how the light intensity was changed. … … [1] (v) The scientists allowed the macroalgae to photosynthesise for 8 minutes in the closed system. They then exchanged the water in the closed system with some of the water in the surrounding tank, before beginning to collect results. Suggest one reason the scientists exchanged the water. … … [1] Table 1.1 shows the results from the investigation. Table 1.1 light intensity oxygen production / μmol mm–2 min–1 / arbitrary units macroalgae species A macroalgae species B 50 650 210 350 1750 580 600 2410 1530 900 2950 3090 1200 2910 3310 (vi) Plot a graph of the two sets of data in Table 1.1 on the grid below and draw an appropriate line for each data set. Complete the axes for the graph. oxygen production / … … [5] (vii) The two species of macroalgae used in the investigation are found at different depths on the mangrove tree roots. Use Table 1.1 to explain the expected depth distribution of the two species of macroalgae on the mangrove tree roots. … … … … … … [3] (viii) At a light intensity of zero the oxygen level decreased during the investigation. Explain this observation. … … … … [2] [Total: 22]

22 marks

Mark scheme: Question Answer Marks 1(a) interactions between, different species / community / biotic factors ; 2 and their (physical), environment / habitat / abiotic factors ; 1(b)(i) Bangladesh ; 1 1(b)(ii) correct reading of two figures from graph ; 2 (protected area  total area)  100 = (value between) 61.34%–70.41% ; 1(b)(iii) any 2 from: 2 global warming / climate change / temperature change ; over-harvesting / deforestation ; storm damage ; change in land use or named example e.g. shrimp farms ; 1(c)(i) carbon dioxide + water → glucose + oxygen ; 1 1(c)(ii) oxygen concentration ; 1 1(c)(iii) any 2 from: 1 temperature (of water) / size, mass, length, of algae / salinity / carbon dioxide / water, type or quality / volume of water or water flow or flow rate (through system) / pH / initial oxygen concentration / colour of light or wavelength ; 1(c)(iv) lamp / light source, moved different distances (from the apparatus) ; 1 1(c)(v) any 1 from: 1 add additional carbon dioxide / remove built up oxygen ; to acclimatise the macroalgae to the conditions before collecting results OWTTE ; 1(c)(vi) both axes labelled with units ; 5 (suitable) linear scale ; points plotted  ½ small square with x or dot in circle ; appropriate lines drawn for both sets of data ; key to identify the 2 data sets ; 1(c)(vii) Any 3 from: 3 species B closer to the surface / species A, can extend to greater depth ; (as species B), require a higher light intensity to photosynthesise / higher rate of photosynthesis than A at shallow depths / lower rate of photosynthesis than A at lower light intensities ORA ; correct ref. to data comparison or manipulation (from their graph) ; the lines cross over at stated light intensity (from their graph) OR the same rate (of photosynthesis) at stated light intensity ; species B may be found at a narrower range of depths / ORA ; both species found near the surface / at high light intensities ; 1(c)(viii) no photosynthesis occurring (as no light) ; 2 respiration uses oxygen ;

This question in 9693/21 Oct/Nov 2023

1 Mangrove forests are important ecosystems. (a) Explain the term ecosystem. … … … … [2] (b) Fig. 1.1 shows the area of mangrove forest in ten countries and the areas of mangrove forest that are protected and unprotected. Key protected mangrove forest unprotected mangrove forest 30 000 25 000 20 000 area of mangrove 15 000 forest / km2 10 000 5000 0 IndonesiaBrazilAustraliaMexicoNigeriaMalaysiaMyanmar GuineaBangladeshCuba New Papua countries Fig. 1.1 (i) State the name of the country which protects the greatest percentage of its mangrove forest. … [1] (ii) Calculate the percentage of mangrove forest in Mexico that is protected. Show your working. … % [2] (iii) State two major threats to mangrove forests. 1 … 2 … [2] (c) Some species of macroalgae grow attached to the roots of mangrove trees. Scientists planned an investigation to compare the rate of photosynthesis at different light intensities in two of these species of macroalgae. (i) State the word equation for photosynthesis. … [1] Fig. 1.2 shows their experimental set-up. This closed system is used to fully contain a standardised volume of water which is circulated. An oxygen sensor recorded oxygen concentration in the water. The whole apparatus was submerged into a much larger tank of sea water for the investigation. circulation pump sealed plastic dome macroalgae grid sealed plastic base dissolved oxygen sensor Fig. 1.2 (ii) Identify the dependent variable. … [1] (iii) Suggest two variables that should be standardised in this investigation. 1 … 2 … [1] (iv) Suggest how the light intensity was changed. … … [1] (v) The scientists allowed the macroalgae to photosynthesise for 8 minutes in the closed system. They then exchanged the water in the closed system with some of the water in the surrounding tank, before beginning to collect results. Suggest one reason the scientists exchanged the water. … … [1] Table 1.1 shows the results from the investigation. Table 1.1 light intensity oxygen production / μmol mm–2 min–1 / arbitrary units macroalgae species A macroalgae species B 50 650 210 350 1750 580 600 2410 1530 900 2950 3090 1200 2910 3310 (vi) Plot a graph of the two sets of data in Table 1.1 on the grid below and draw an appropriate line for each data set. Complete the axes for the graph. oxygen production / … … [5] (vii) The two species of macroalgae used in the investigation are found at different depths on the mangrove tree roots. Use Table 1.1 to explain the expected depth distribution of the two species of macroalgae on the mangrove tree roots. … … … … … … [3] (viii) At a light intensity of zero the oxygen level decreased during the investigation. Explain this observation. … … … … [2] [Total: 22]

22 marks

Mark scheme: Question Answer Marks 1(a) interactions between, different species / community / biotic factors ; 2 and their (physical), environment / habitat / abiotic factors ; 1(b)(i) Bangladesh ; 1 1(b)(ii) correct reading of two figures from graph ; 2 (protected area  total area)  100 = (value between) 61.34%–70.41% ; 1(b)(iii) any 2 from: 2 global warming / climate change / temperature change ; over-harvesting / deforestation ; storm damage ; change in land use or named example e.g. shrimp farms ; 1(c)(i) carbon dioxide + water → glucose + oxygen ; 1 1(c)(ii) oxygen concentration ; 1 1(c)(iii) any 2 from: 1 temperature (of water) / size, mass, length, of algae / salinity / carbon dioxide / water, type or quality / volume of water or water flow or flow rate (through system) / pH / initial oxygen concentration / colour of light or wavelength ; 1(c)(iv) lamp / light source, moved different distances (from the apparatus) ; 1 1(c)(v) any 1 from: 1 add additional carbon dioxide / remove built up oxygen ; to acclimatise the macroalgae to the conditions before collecting results OWTTE ; 1(c)(vi) both axes labelled with units ; 5 (suitable) linear scale ; points plotted  ½ small square with x or dot in circle ; appropriate lines drawn for both sets of data ; key to identify the 2 data sets ; 1(c)(vii) Any 3 from: 3 species B closer to the surface / species A, can extend to greater depth ; (as species B), require a higher light intensity to photosynthesise / higher rate of photosynthesis than A at shallow depths / lower rate of photosynthesis than A at lower light intensities ORA ; correct ref. to data comparison or manipulation (from their graph) ; the lines cross over at stated light intensity (from their graph) OR the same rate (of photosynthesis) at stated light intensity ; species B may be found at a narrower range of depths / ORA ; both species found near the surface / at high light intensities ; 1(c)(viii) no photosynthesis occurring (as no light) ; 2 respiration uses oxygen ;

This question in 9693/22 Oct/Nov 2023

5 Weathering and erosion affect the shape and structure of coastlines and shores. (a) (i) Explain the difference between weathering and erosion. … … … … [2] (ii) Erosion can be caused by the action of water. State two other causes of erosion. 1 … 2 … [2] (b) Scientists investigated the effect of sediment diameter on sinking speed during deposition. Sediments of three different diameters, 1 mm, 3 mm and 5 mm, were allowed to fall through a cylinder of sea water. Data loggers were used to record their sinking speed over time. Fig. 5.1 shows the mean results from the investigation. 1.1 Key 5mm 1.0 3mm 1mm 0.9 0.8 0.7 0.6sinking speed /ms–1 0.5 0.4 0.3 0.2 0.1 0 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 time/s Fig. 5.1 (i) Calculate the maximum difference in sinking speed for sediments of 1 mm and 5 mm diameter. difference in sinking speed = … m s–1 [1] (ii) Use Fig. 5.1 to compare the effect of sediment diameter on sinking speed. … … … … … … [3] (iii) Suggest one factor, other than diameter, that will affect the sinking speed of sediments. … … [1] (c) Mangrove forests are tidal ecosystems which have a major influence on biodiversity and the distribution of sediments. (i) Explain how mangrove forests affect the distribution of sediments. … … … … [2] (ii) Other than increasing biodiversity, explain the ecological importance of mangrove forests trapping sediments. … … … … [2] [Total: 13]

13 marks

Mark scheme: 5(a)(i) weathering, wears away / breaks down /dissolves, rocks ; 2 erosion is the, movement / transport, of sediments ; 5(a)(ii) any two from: 2 wind ; ice / glacial erosion ; gravity ; 5(b)(i) 1.07 – 0.51 = 0.56 ; 1 5(b)(ii) any three from: 3 sinking speed the same for all diameters initially ; the smaller the diameter the lower the maximum sinking speed ORA ; the smallest diameter reaches maximum sinking speed sooner ORA ; the larger the sediments the less the difference in maximum sinking speed ORA ; correct use of manipulated data ; 5(b)(iii) any one from: 1 density of particle material ; temperature of the water / fluid ; shape / texture, of each particle sinking ; movement of water ; density of the water / fluid ; 5(c)(i) any two from: 2 prop roots ; help slow, water flow / current speed ; allows increased deposition / sedimentation ; stabilise settled sediments ; 5(c)(ii) any two from: 2 stabilises / protects, coastline ; prevents sediment build up on coral reefs / seagrass beds ; (removing sediment) increases light intensity in open ocean for phytoplankton ;

This question in 9693/22 Oct/Nov 2025

5 Weathering and erosion affect the shape and structure of coastlines and shores. (a) (i) Explain the difference between weathering and erosion. … … … … [2] (ii) Erosion can be caused by the action of water. State two other causes of erosion. 1 … 2 … [2] (b) Scientists investigated the effect of sediment diameter on sinking speed during deposition. Sediments of three different diameters, 1 mm, 3 mm and 5 mm, were allowed to fall through a cylinder of sea water. Data loggers were used to record their sinking speed over time. Fig. 5.1 shows the mean results from the investigation. 1.1 Key 5mm 1.0 3mm 1mm 0.9 0.8 0.7 0.6sinking speed /ms–1 0.5 0.4 0.3 0.2 0.1 0 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 time/s Fig. 5.1 (i) Calculate the maximum difference in sinking speed for sediments of 1 mm and 5 mm diameter. difference in sinking speed = … m s–1 [1] (ii) Use Fig. 5.1 to compare the effect of sediment diameter on sinking speed. … … … … … … [3] (iii) Suggest one factor, other than diameter, that will affect the sinking speed of sediments. … … [1] (c) Mangrove forests are tidal ecosystems which have a major influence on biodiversity and the distribution of sediments. (i) Explain how mangrove forests affect the distribution of sediments. … … … … [2] (ii) Other than increasing biodiversity, explain the ecological importance of mangrove forests trapping sediments. … … … … [2] [Total: 13]

13 marks

Mark scheme: 5(a)(i) weathering, wears away / breaks down /dissolves, rocks ; 2 erosion is the, movement / transport, of sediments ; 5(a)(ii) any two from: 2 wind ; ice / glacial erosion ; gravity ; 5(b)(i) 1.07 – 0.51 = 0.56 ; 1 5(b)(ii) any three from: 3 sinking speed the same for all diameters initially ; the smaller the diameter the lower the maximum sinking speed ORA ; the smallest diameter reaches maximum sinking speed sooner ORA ; the larger the sediments the less the difference in maximum sinking speed ORA ; correct use of manipulated data ; 5(b)(iii) any one from: 1 density of particle material ; temperature of the water / fluid ; shape / texture, of each particle sinking ; movement of water ; density of the water / fluid ; 5(c)(i) any two from: 2 prop roots ; help slow, water flow / current speed ; allows increased deposition / sedimentation ; stabilise settled sediments ; 5(c)(ii) any two from: 2 stabilises / protects, coastline ; prevents sediment build up on coral reefs / seagrass beds ; (removing sediment) increases light intensity in open ocean for phytoplankton ;

This question in 9693/23 Oct/Nov 2025