Nutrient Cycling MCQs (Quiz 9) Posted on May 30, 2026Author agropublishers 0 1. Acid rain mainly affects structures made of ___________________ Sandstone and shale Granite and quartzite Basalt and gabbro Limestone and marble 2. When a leaf falls to the forest floor and fungi and bacteria break it down, what is the key outcome for the ecosystem? Nutrients locked in the dead leaf are released as inorganic ions, making them available to plants again Carbon dioxide is absorbed from the atmosphere into the leaf material New organic proteins are synthesized and passed to herbivores Solar energy trapped in the leaf is converted into heat permanently 3. Which weathering agent is most responsible for forming rounded river pebbles? Plant roots Carbon dioxide Flowing water and abrasion Oxygen 4. Which essential plant nutrient is commonly released through weathering of feldspar minerals? Nitrogen Potassium Phosphorus Sulfur 5. When forests are burned, carbon stored in biomass is primarily released as ________________ Methane Carbon dioxide Oxygen gas Nitrogen gas 6. Why is the phosphorus cycle described as sedimentary rather than gaseous, unlike the carbon and nitrogen cycles? Living organisms convert all available phosphorus into organic compounds permanently Ocean currents prevent phosphorus from entering the atmosphere Phosphorus reacts with oxygen in the atmosphere and is rapidly destroyed Phosphorus has no stable gaseous form under normal conditions, so it cycles mainly through rocks, soil, water, and living organisms 7. Which of the following processes represents assimilation in the nitrogen cycle? Anaerobic bacteria reducing nitrates into nitrogen gas Decomposers breaking down dead organic matter into ammonium ions Bacteria converting ammonia into nitrites in the soil Plants absorbing nitrate ions and incorporating them into amino acids and proteins 8. Two groups of bacteria are involved in nitrification. Which pair correctly performs the two oxidation steps? Nitrobacter converts NH₄⁺ to NO₂⁻; Nitrosomonas converts NO₂⁻ to NO₃⁻ Nitrosomonas converts NH₄⁺ to NO₂⁻; Nitrobacter converts NO₂⁻ to NO₃⁻ Rhizobium converts NH₄⁺ to NO₂⁻; Pseudomonas converts NO₂⁻ to NO₃⁻ Azotobacter converts NH₄⁺ to NO₂⁻; Rhizobium converts NO₂⁻ to NO₃⁻ 9. Which organism is often the first colonizer of bare rock surfaces? Trees Shrubs Lichens Grass 10. When soil microorganisms take up mineral nutrients and lock them into their own body tissues, making them temporarily unavailable to plants, this is called ________________ Assimilation Denitrification Nutrient immobilization Leaching Loading … Question 1 of 10
