Oceanography and Marine Biology MCQs 50 Score: 0 Attempted: 0/50 Subscribe 1. : What percentage of Earth’s surface is covered by oceans? (A) 50% (B) 60% (C) 70% (D) 80% 2. : Which ocean is the largest by area? (A) Atlantic Ocean (B) Indian Ocean (C) Arctic Ocean (D) Pacific Ocean 3. : What is the study of the physical and biological aspects of the ocean called? (A) Geology (B) Oceanography (C) Meteorology (D) Astronomy 4. : Which marine zone is closest to the shore and is affected by tides? (A) Pelagic zone (B) Abyssal zone (C) Intertidal zone (D) Hadal zone 5. : What type of organism forms the base of most ocean food chains? (A) Zooplankton (B) Phytoplankton (C) Fish (D) Coral 6. : What is the name of the largest coral reef system in the world? (A) Red Sea Reef (B) Great Barrier Reef (C) Mesoamerican Reef (D) Belize Barrier Reef 7. : Which oceanic feature is a deep valley on the ocean floor? (A) Continental shelf (B) Ocean trench (C) Seamount (D) Abyssal plain 8. : What is the primary cause of ocean tides? (A) Wind (B) Earth’s rotation (C) Gravitational pull of the moon (D) Underwater earthquakes 9. : What is the term for the warm, nutrient-poor surface layer of the ocean? (A) Thermocline (B) Mixed layer (C) Euphotic zone (D) Epipelagic zone 10. : Which gas is most abundant in seawater? (A) Oxygen (B) Nitrogen (C) Carbon dioxide (D) Hydrogen 11. : What marine animals build calcium carbonate shells? (A) Jellyfish (B) Mollusks (C) Sea stars (D) Sharks 12. : What process do marine plants use to convert sunlight into energy? (A) Photosynthesis (B) Respiration (C) Fermentation (D) Chemosynthesis 13. : Which ocean zone is known as the “midnight zone” where no sunlight penetrates? (A) Mesopelagic (B) Bathypelagic (C) Abyssopelagic (D) Hadalpelagic 14. : Hydrothermal vents are primarily found at which oceanic feature? (A) Ocean trenches (B) Mid-ocean ridges (C) Continental shelves (D) Abyssal plains 15. : Which is the largest marine mammal? (A) Orca (B) Blue whale (C) Humpback whale (D) Sperm whale 16. : What is the function of bioluminescence in marine animals? (A) Photosynthesis (B) Attract prey or mates (C) Respiration (D) Defense against bacteria 17. : What type of plankton are small drifting animals in the ocean? (A) Phytoplankton (B) Zooplankton (C) Bacterioplankton (D) Viruses 18. : Which of the following is a key nutrient for marine plant growth? (A) Oxygen (B) Phosphorus (C) Calcium (D) Helium 19. : The process where seawater becomes denser due to cooling or increased salinity is called: (A) Evaporation (B) Upwelling (C) Thermohaline circulation (D) Diffusion 20. : Which part of a sea turtle’s body helps it to swim efficiently? (A) Flippers (B) Claws (C) Tail (D) Shell 21. : What is the name of the floating community of organisms at the ocean’s surface? (A) Benthic community (B) Pelagic community (C) Neuston (D) Nekton 22. : Which ocean layer contains the highest pressure? (A) Surface layer (B) Thermocline (C) Abyssal zone (D) Epipelagic zone 23. : What is the term for animals that live on or in the seabed? (A) Pelagic (B) Nekton (C) Benthic (D) Planktonic 24. : What is the main cause of ocean currents? (A) Tides and moon gravity (B) Wind and Earth’s rotation (C) Salinity only (D) Pressure from marine animals 25. : Which of these is a filter-feeding marine animal? (A) Shark (B) Clam (C) Dolphin (D) Octopus 26. : Which marine plant is known as “sea grass”? (A) Kelp (B) Mangrove (C) Phytoplankton (D) Seagrass 27. : What is the main component of coral reefs? (A) Silica (B) Calcium carbonate (C) Salt (D) Sand 28. : The deepest part of the ocean is known as the: (A) Continental slope (B) Abyssal plain (C) Ocean trench (D) Seamount 29. : Which gas dissolves in seawater to create carbonic acid? (A) Oxygen (B) Carbon dioxide (C) Nitrogen (D) Methane 30. : What is a major threat to coral reefs worldwide? (A) Overfishing (B) Coral bleaching (C) Plastic pollution (D) All of the above 31. : Which fish is known for its ability to generate electric shocks? (A) Electric eel (B) Barracuda (C) Clownfish (D) Anglerfish 32. : Which type of symmetry do most adult echinoderms exhibit? (A) Bilateral (B) Radial (C) Asymmetrical (D) Spherical 33. : Mangrove forests are important because they: (A) Prevent coastal erosion (B) Provide nursery habitats (C) Act as carbon sinks (D) All of the above 34. : What causes ocean acidification? (A) Increased salt content (B) Increased dissolved CO2 (C) Increased temperature (D) Decreased oxygen 35. : What kind of feeders are baleen whales? (A) Carnivores (B) Filter feeders (C) Herbivores (D) Omnivores 36. : Which of the following is a pelagic fish? (A) Flounder (B) Tuna (C) Crab (D) Lobster 37. : The process by which nutrients from deep water rise to the surface is called: (A) Downwelling (B) Upwelling (C) Thermohaline circulation (D) Tidal flow 38. : Which ocean zone supports the greatest biodiversity? (A) Abyssal zone (B) Intertidal zone (C) Hadal zone (D) Bathypelagic zone 39. : What kind of organism is a krill? (A) Fish (B) Crustacean (C) Mollusk (D) Algae 40. : What is a characteristic of plankton? (A) They actively swim against currents (B) They are free-floating organisms (C) They live only on the seabed (D) They are all animals 41. : Which part of the ocean floor is relatively flat and extends from the shore? (A) Continental shelf (B) Seamount (C) Trench (D) Abyssal plain 42. : What type of reproduction is common in marine corals? (A) Sexual and asexual (B) Only sexual (C) Only asexual (D) Budding only 43. : What is the main source of energy for hydrothermal vent communities? (A) Sunlight (B) Photosynthesis (C) Chemosynthesis (D) Heat from the sun 44. : Which marine animal has tentacles with stinging cells called nematocysts? (A) Starfish (B) Jellyfish (C) Clam (D) Crab 45. : What is the salinity of average seawater? (A) 15 ppt (B) 30 ppt (C) 35 ppt (D) 50 ppt 46. : What is the name for the large circular current systems in the oceans? (A) Tides (B) Gyres (C) Waves (D) Upwellings 47. : Which of these animals is a nekton? (A) Plankton (B) Shark (C) Coral (D) Seaweed 48. : The ocean’s biological pump helps in: (A) Heat circulation (B) Carbon sequestration (C) Salt regulation (D) Nutrient depletion 49. : Which layer of the ocean has the steepest temperature gradient? (A) Surface mixed layer (B) Thermocline (C) Deep ocean (D) Abyssal zone 50. : What is the main purpose of mangrove roots? (A) Absorb salt (B) Stabilize shorelines (C) Provide habitat (D) All of the above