Oceans and Life: 20 flashcards
All 20 flashcards from this kit, free and with no sign-up.
1. What percentage of Earth's surface is covered by the ocean?
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About 71%
2. What percentage of Earth's water is held by the ocean?
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About 97%
3. What is the sunlit zone also called?
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The euphotic zone
4. Up to what depth does the sunlit (euphotic) zone extend?
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About 200 m
5. What are phytoplankton?
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Microscopic photosynthetic organisms that form the base of the marine food web
6. What do zooplankton feed on?
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Phytoplankton
7. What is the depth range of the twilight (mesopelagic) zone?
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200–1000 m
8. Can photosynthesis occur in the twilight zone?
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No — light is too faint
9. What is the depth range of the dark (bathypelagic) zone?
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1000–4000 m
10. What is bioluminescence?
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The ability of organisms to produce their own light, used for hunting and defence
11. What process supports life at hydrothermal vents?
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Chemosynthesis — bacteria use chemicals like hydrogen sulphide to make food
12. What two factors affect water density and drive ocean currents?
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Salinity and temperature
13. What is thermohaline circulation?
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The global movement of ocean water driven by differences in temperature and salinity
14. How does the ocean buffer climate change?
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It absorbs carbon dioxide and heat from the atmosphere
15. Name three human threats to ocean life.
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Overfishing, plastic pollution, oil spills (also nutrient runoff and climate change)
16. What causes algal blooms that create dead zones?
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Nutrient runoff from farms
17. What is ocean acidification and what does it stress?
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The ocean becoming more acidic due to absorbed CO₂; it stresses corals and shell-forming organisms
18. What is the abyssal zone's depth range?
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4000–6000 m
19. Give one adaptation of deep-sea organisms to high pressure.
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No gas-filled swim bladders; flexible, watery tissues
20. Why is the ocean central to the water cycle?
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The Sun evaporates seawater; vapour condenses into clouds and falls as freshwater rain
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