14 public questions tagged with this topic.
Tropical rainforests have the highest net primary productivity due to their high biodiversity, warm climate, and abundant rainfall.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
Primary productivity varies across ecosystems and is influenced by factors such as sunlight, nutrient availability, and temperature.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
Net Primary Productivity (NPP) is the amount of energy left after plants use some for respiration (R), calculated as NPP = GPP - R.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
NPP is always less than GPP because it accounts for the energy lost through respiration.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
Tropical rainforests have the highest net primary productivity per unit area due to abundant sunlight, water, and nutrient availability.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
NPP is the energy available to herbivores after accounting for the energy used in respiration by plants.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
NPP is always less than GPP because it accounts for the energy used in respiration by plants.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Productivity - Primary Secondary GPP NPP
Open-ocean producers have very low standing biomass but extremely rapid turnover. Small phytoplankton cells divide quickly, experience efficient nutrient exchange, and are continually consumed, so annual net primary production can be large relative to the biomass present at any one sampling time. 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, Ocean, 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
Net primary productivity is the rate at which producers accumulate new organic matter after meeting their own respiratory costs. Gross primary productivity represents all carbon fixed or energy captured by autotrophs. Autotrophic respiration consumes part of that material to support cellular maintenance, active transport, tissue construction, and repair. The balance is therefore NPP = GPP − R, where R in this formula means respiration by primary producers, often written Ra. NPP supplies plant growth and reproduction and is the energy potentially available to herbivores and decomposers. Adding respiration would count respired carbon as retained production, while reversing the subtraction could yield a biologically meaningless negative value. Division by respiration is a ratio, not a production rate. This equation must also be distinguished from net ecosystem production, which subtracts both autotrophic and heterotrophic respiration from GPP. The carbon-balance mechanism explains the sign: photosynthesis adds organic carbon to producer biomass, whereas respiration oxidizes some organic carbon and returns carbon dioxide, leaving the difference as net production.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17
“Deserts < Temperate forests < Tropical forests” for npp per unit leaf area increases in. 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—“Deserts < Tropical forests < Temperate forests”, “Temperate forests < Tropical forests < Deserts”, “Tropical forests < Temperate forests < Deserts”—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.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
The sequence hot deserts below temperate grasslands below tropical forests is a plausible increasing order of daily plant productivity per unit leaf area. Desert productivity is constrained by water shortage, heat, and short growth windows. Temperate grasslands gain more consistently during favourable seasons but face winter or drought, while tropical forests benefit from warm conditions and long growing periods. This metric should not be confused with standing biomass or productivity per unit ground area. Climate, nutrients, disturbance, species traits, and food-web structure interact, so broad ecological generalisations describe tendencies rather than universal rules. Energy is lost as metabolic heat at every trophic transfer, while elements such as nitrogen and phosphorus are recycled through organisms and the physical environment. Mechanistic interpretation connects individual physiology and species interactions to population change, community composition, and ecosystem-level fluxes. Reliable inference requires the complete experimental design, definitions, units, and statistical evidence; missing labels cannot be reconstructed from an answer key alone.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
The workbook attributes age-related decline in tree net primary productivity to statements A, B, and C, but their contents are omitted. Established mechanisms include greater respiratory maintenance costs as living biomass increases, hydraulic limitation over longer transport paths, nutrient constraints, changing allocation, and reduced photosynthetic capacity or leaf-area efficiency. No single mechanism explains every species and stand. Because the three assertions are unavailable, their combined selection cannot be scientifically verified from this row alone. Net primary production equals gross primary production minus plant respiration and represents biomass or energy made available for growth and consumers. Rates must be compared on the same area, biomass, leaf-area, and time basis because changing the denominator can reverse an apparent ecosystem ranking. Climate, nutrients, disturbance, species traits, and food-web structure interact, so broad ecological generalisations describe tendencies rather than universal rules. Energy is lost as metabolic heat at every trophic transfer, while elements such as nitrogen and phosphorus are recycled through organisms and the physical environment.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
