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