17 public questions tagged with this topic.
Nutrients are not lost permanently; they are continuously recycled in ecosystems.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Nutrient Cycling - Carbon Phosphorus and Ecological Succession
Nitrogen fixation by bacteria converts atmospheric nitrogen (Nâ) into ammonia (NHâ), making it available for plant uptake.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Adaptations - Morphological Physiological Behavioural
Photosynthesis removes carbon dioxide from the atmosphere, while respiration releases it back, driving the carbon cycle.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Organism and Environment - Major Biomes Abiotic Factors
Nitrogen fixation by bacteria converts atmospheric nitrogen into ammonia, which can be used by plants.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Organism and Environment - Major Biomes Abiotic Factors
Biogeochemical cycles connect biological uptake, trophic transfer, decomposition, mineralization, and abiotic reservoirs of elements such as carbon, nitrogen, and phosphorus. Because these transfers are studied together with energy flow at the level of whole ecological systems, they belong to ecosystem ecology. Primary production supports heterotrophic food webs by converting external energy into chemical energy stored in organic matter. The fate of that energy depends on maintenance respiration, growth, consumption, death, and decomposition. Carbon can be tracked as gross fixation, producer biomass increment, or whole-system accumulation, and each quantity has a different equation. Because respiration irreversibly dissipates usable energy as heat, energy moves directionally through trophic levels even though nutrients released by decomposers may cycle repeatedly. In this context, the keyed term, Ecosystem ecology, identifies the relevant mechanism or quantitative relationship and links the observed pattern to its underlying ecological cause. The distinction is testable by measuring changes in organisms, resources, or process rates through time rather than relying on the label alone.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17
“Phosphorus” for which biogeochemical cycle is open due to loss to oceans. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. The relevant inference should follow the pathway from resource supply to organismal uptake and then to ecosystem-level flux. Productivity, trophic transfer, decomposition, and nutrient regeneration are connected, but each measures a different part of that pathway. The remaining alternatives—“Carbon”, “Nitrogen”, “Sulfur”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
“Bacteria” for which organism group performs nitrification. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Fungi”, “Algae”, “Protozoa”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
“Anaerobic” for denitrification requires what condition. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Aerobic”, “Sunlight”, “Cold temperature”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
“Rocks and sediments” for the largest reservoir of phosphorus is found in. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Atmosphere”, “Ocean”, “Plants”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
“Phosphorus” for which element’s overabundance causes algal blooms and fish kills. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The remaining alternatives—“Carbon”, “Sulfur”, “Nitrogen”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The relevant inference should follow the pathway from resource supply to organismal uptake and then to ecosystem-level flux. Productivity, trophic transfer, decomposition, and nutrient regeneration are connected, but each measures a different part of that pathway. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
“Soil and rocks” for sedimentary biogeochemical cycles have their main pool in. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Atmosphere”, “Living biomass”, “Ocean surface”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
The keyed exception is “Nitrite.” In the context of which component is not part of the sulfur cycle, that statement differs from the governing ecological pattern and must be evaluated against the mechanism rather than accepted from wording alone. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The remaining alternatives—“Sulfate”, “Sulfur dioxide”, “Hydrogen sulfide”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The relevant inference should follow the pathway from resource supply to organismal uptake and then to ecosystem-level flux. Productivity, trophic transfer, decomposition, and nutrient regeneration are connected, but each measures a different part of that pathway. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 18
