Paper Practice: Coral Reefs and Lagoons

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The list below gives some of the stages in the formation of an atoll.
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barrier reef forms, island subsides, fringing reef develops on a volcanic island, atoll forms
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State three factors involved in the formation of atolls.
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coral growth; subsidence/island/volcano sinks; erosion/wave action/energy; changes in sea levels; sedimentation/owtte;
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State two methods used to date reefs.
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any 2 of: carbon dating; drilling/core sampling; rock analysis/geomorphology;
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Suggest why the corals grown in a laboratory need to be illuminated.
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ref to the presence of zooxanthellae/eq in corals; need light for photosynthesis/eq; [2]
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The coral growing on the sunken ship receives more light in the summer than the coral growing in the laboratory at 24 °C. Describe how this hypothesis could be tested. Your answer should include references to the collection of quantitative results.
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reference to use of a light meter/light probe/eq; measure light intensity in sea next to wreck/where coral is growing; take measurements at different time of the day; take measurements on different days (during the summer); measure light intensity in laboratory; ref to measuring light duration; [4]
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Suggest three factors, other than temperature and light, which may affect the growth of coral in the marine environment. For each factor, predict its possible effect on growth.
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availability of food/nutrients; increase in food will increase growth; depth in water; growth decreases with increased depth; presence of predators/competitors; predators will decrease growth; ACCEPT appropriate converse effects on growth Note: other factors could include: turbidity of water; pH of sea water; dissolved oxygen; sedimentation; pollution; salinity; disease; carbon dioxide; wave action; [6]
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What are 3 factors that contribute to the erosion of coral reefs(3)
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wave action, action of other organisms, human activity, acid, storms
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How is carbon dating used to recreate the history of coral reefs(5)
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reference to radioactive isotope carbon-14, taken during photosynthesis and [asses through food chain, reference to constant proportion carbon-14 atoms to carbon-12 atoms, reference to same proportion of carbon-14 as atmosphere, reference to carbon-14 decays, half-life, dead organisms stop taking in carbon-14 atoms, ratio of carbon-14 to carbon-12 in a living thing is a constant, count number of carbon-14 atoms, compare with original atoms, calculate age
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Why do coral reefs need clear water without silt for maximum growth(2)
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silt erduces light penetration, inhabit the photosynthesis of symbiotic relationship with algae, ora
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How do artificial reefs boost the economy(2)
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new fishing/diving, boost ecotourism, business benefit increased spending
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Describe the Darwin-Dana-Daly theory of atoll formation
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fringing reef on volcanic island; land sinks/ subsidence; barrier reef forms; island sinks below sea level; atoll formed;
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Name three methods used for the reconstruction of the history of coral reefs
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drilling; geomorphological analysis; carbon dating;
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Suggest three reasons for the use of artificial reefs
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prevents erosion of land; provides anchorages/protection for harbours; provides new habitats; increases fishing areas; reference to tourism/diving;
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Describe the relationship between corals and zooxanthellae
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1 symbiosis / mutualism ; 2 corals are, animals / heterotrophic ; 3 zooxanthellae are single-celled, plants / organisms ; 4 photosynthesise ; 5 provide nutrients for coral animals ; 6 examples of nutrients (e.g. carbohydrates) ; 7 coral growth pattern provides large surface area ; 8 for maximum absorption of light (by zooxanthellae) ; 9 products of digestion by corals provide minerals / nutrients, for zooxanthellae ; 10 other valid points
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Discuss the possible reasons for the very high biodiversity on coral reefs
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1 high productivity ; 2 grow in regions of warm temperature and high light intensity ; 3 very high efficiency of energy transfer between zooxanthellae and corals / producers and primary consumers ; 4 so can support many different, secondary consumers / predators ; 5 long food chains possible (because of lower energy losses) ; 6 relatively stable environment ; 7 many different niches ;8 examples of niches / organisms that use them ; 9 other valid points
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Suggest how sedimentation can reduce coral growth
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sediment covers coral polyp; plus any two of: prevents feeding; less light can reach zooxanthellae; reduced/little photosynthesis;
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Suggest how an increase in carbon dioxide in the atmosphere can damage coral
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carbon dioxide dissolves in sea water; sea water becomes acidic; dissolves coral skeleton;
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State three reasons for the use of artificial reefs.
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create new habitat for marine organisms; reference to tourism/fishing/diving; prevent erosion of shore; dissipate energy of waves; protect anchorages; reference to research/owtte;
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Explain why the death of zooxanthellae results in coral bleaching
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zooxanthellae contain, pigment / chlorophyll ;
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Explain why the death of the zooxanthellae may lead to the death of the coral
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zooxanthellae photosynthesise ; produce, sugars / carbohydrates / other named substance ; coral (animals) rely on this as nutrient source ; ref to effect of zoonxanthellae on calcium carbonate deposition

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