Ecosystem Ecology & PRODUCTIVITY

Ecosystem Ecology & PRODUCTIVITY

Which of the following expresses productivity and NOT biomass?

Productivity is a rate of biomass or carbon production and therefore requires dimensions of mass per area per time. Grams per square metre per day includes the essential time denominator, whereas grams per square metre, kilograms per hectare, and grams dry weight describe standing amount rather than production rate. Carbon accounting separates gross fixation from respiratory expenditure. Gross primary productivity records all photosynthetic carbon fixation; net primary productivity subtracts autotrophic respiration, while net community productivity subtracts total ecosystem respiration. Keepin

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Chemoautotrophs are mainly responsible for primary productivity in:

At deep-sea hydrothermal vents sunlight is absent, but reduced chemicals such as hydrogen sulfide and hydrogen provide usable energy. Chemolithoautotrophic bacteria and archaea oxidize these compounds and use the released energy to fix inorganic carbon, supporting food webs independent of photosynthesis. 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

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Decomposition mainly occurs in:

Topsoil usually contains the greatest concentration of fresh litter, fine roots, oxygen, moisture, and decomposer organisms. Fungi, bacteria, and detritivores fragment and enzymatically break down dead organic material there, releasing mineral nutrients and converting part of the carbon into microbial biomass or carbon dioxide. Ecosystem production is measured over a stated area and interval because it is a flux, not simply material present at one moment. Producers convert inorganic carbon into organic compounds, respiration returns some carbon to the environment, and heterotrophs redistribute

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Energy transfer from one trophic level to another is termed:

Energy flow describes the directional transfer of chemical energy through feeding relationships, beginning with energy captured by primary producers and continuing through consumers and decomposers. Unlike matter, energy is not recycled indefinitely; metabolic work ultimately dissipates much of it as heat. Carbon accounting separates gross fixation from respiratory expenditure. Gross primary productivity records all photosynthetic carbon fixation; net primary productivity subtracts autotrophic respiration, while net community productivity subtracts total ecosystem respiration. Keeping fluxes d

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

The study of biogeochemical cycles falls under:

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 b

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Which of these is not an autotroph?

Fungi obtain organic carbon by secreting extracellular enzymes and absorbing the resulting soluble compounds. They lack photosynthetic pigments and do not fix inorganic carbon as their principal carbon source, unlike cyanobacteria, algae, and photosynthetic members of the phytoplankton. Ecosystem production is measured over a stated area and interval because it is a flux, not simply material present at one moment. Producers convert inorganic carbon into organic compounds, respiration returns some carbon to the environment, and heterotrophs redistribute and mineralize the remainder. Aquatic and

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

The most productive aquatic system is:

Estuaries commonly sustain exceptionally high areal primary productivity because river inputs, tidal mixing, and sediment regeneration continuously supply nutrients to shallow, well-lit water. Marsh plants, seagrasses, benthic algae, and phytoplankton may all contribute, while tidal exchange prevents persistent nutrient exhaustion. Carbon accounting separates gross fixation from respiratory expenditure. Gross primary productivity records all photosynthetic carbon fixation; net primary productivity subtracts autotrophic respiration, while net community productivity subtracts total ecosystem res

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Which of the following has the highest NPP per unit biomass?

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 incremen

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Autotrophic respiration is abbreviated as:

Autotrophic respiration is conventionally written RA because it is respiration performed by primary producers. It represents carbon fixed by photosynthesis that plants or other autotrophs consume for maintenance, ion uptake, biosynthesis, growth, and tissue turnover rather than retaining as new biomass. Ecosystem production is measured over a stated area and interval because it is a flux, not simply material present at one moment. Producers convert inorganic carbon into organic compounds, respiration returns some carbon to the environment, and heterotrophs redistribute and mineralize the remai

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Net Community Productivity (NCP) is:

Net community productivity is the net rate at which organic carbon accumulates in an ecosystem after respiration by both autotrophs and heterotrophs. Ecosystem respiration, RE, includes plant respiration plus respiration by consumers and decomposers, so subtracting RE from gross primary productivity gives NCP. Carbon accounting separates gross fixation from respiratory expenditure. Gross primary productivity records all photosynthetic carbon fixation; net primary productivity subtracts autotrophic respiration, while net community productivity subtracts total ecosystem respiration. Keeping flux

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

The total ecosystem respiration (RE) is:

Total ecosystem respiration, RE, is the combined carbon dioxide release from autotrophic respiration, RA, and heterotrophic respiration, RH. Autotrophs respire to maintain and build plant, algal, or microbial tissues; heterotrophs—including animals, fungi, and many bacteria—respire while consuming living or dead organic matter. Adding these fluxes gives RE = RA + RH. Gross primary productivity removes CO2 from the atmosphere or water through carbon fixation, whereas ecosystem respiration returns CO2 through oxidation of organic carbon. Their difference defines net ecosystem production: NEP = G

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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Ecosystem Ecology & PRODUCTIVITY

Which is NOT a type of biocenose?

Biocenosis means the interacting living community within a habitat. Standard organism-based subdivisions include zoocenosis for animals, phytocenosis for plants, microbiocenosis for microorganisms, and sometimes mycocenosis for fungi. Terms such as hydrocenosis can describe a community in water, while pedocenosis can describe a soil community; these are habitat-based labels rather than universally standardized taxonomic subdivisions. Consequently, selecting hydrocenosis as the sole item that is “not a type” is not scientifically well supported, because aquatic communities are valid biocenoses

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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