Week 8: Flux of Energy & Matter Flashcards
Standing crop
The bodies of the living organisms within a unit area constitute a standing crop of
biomass.
Biomass
The mass of organisms per unit area of ground (or water), usually expressed
in units of energy (such as joules per square meter),
dry organic matter (grams per square meter), or mass of carbon (grams of carbon per square meter).
Primary productivity
The rate at which biomass is produced per unit area or volume through photosynthesis. Like biomass, it can be expressed in many different units, including energy (such as joules per square meter per day, or per year), dry organic matter (grams per square meter per day), or mass of carbon (grams carbon per square meter per day). Ecologists consider both gross primary pro- ductivity and net primary productivity.
Gross primary productivity
The total fixation of energy by photosynthesis. A proportion of this, however, is respired away by the primary producer organisms (the autotrophs) themselves and is lost from the ecosystem as respiratory heat (R_auto)
Respiratory heat (R_auto)
The production portion of carbon dioxide in an ecosystem’s carbon flux, while photosynthesis typically accounts for the majority of the ecosystem’s carbon consumption.
Net Primary Productivity
This is the difference between GPP and R_auto. It represents the actual rate of production of new biomass that is available for consumption by heterotrophic organisms (bacteria, fungi, and animals).
Secondary productivity
The rate of production of biomass by heterotrophs.
Net ecosystem productivity
Net ecosystem
productivity is the difference between GPP and the respiration of all organisms in an ecosystem (R auto)- It measures the net rate of accumulation or loss of
organic matter, energy, or organic carbon from the ecosystem and is equivalent to the rate of NPP minus the respiration of all heterotrophic organisms (R het).
Live consumer system
A proportion of primary
production is consumed by herbivores, which, in turn, are consumed by carnivores.
Decomposer system
The fraction of NPP that is not eaten by herbivores
Decomposer
Fungi, bacteria, invertebrates such as worms and insects have the ability to break down dead organisms into smaller particles and create new compounds.
Detritivore
Nnimals that consume dead matter
Colimitation
In some ecosystems, both nitrogen and phosphorus are limiting to production.
Eutrophication
The process of excess nutrient enrichment.
Positive feedback
Occurs to increase the change or output.
Transfer efficiencies
The proportions of net primary production flowing along
each of the possible energy pathways.
Consumption efficiency (CE)
The percentage of total productivity available at one trophic level that is consumed (‘ingested’) by the trophic level above. For primary consumers, CE is the percentage of joules (or organic carbon, which is the source of the potential energy) produced per unit time and area as NPP that finds its way into the guts of herbivores. In the case of secondary consumers, it is the percentage of herbivore productivity eaten by carnivores. The remainder dies without being eaten and enters the decomposer system. Reasonable average values for CE by herbivores are approximately 5% in forests, 25% in grasslands, and 50% in phytoplankton-dominated communities. For carnivores, CE varies from 25% to almost 100%.
Production efficiency (PE)
The percentage of assimilated energy incorporated into new biomass; the remainder is entirely lost to the community as respira- tory heat. PE varies according to the taxonomic class of the organisms concerned. Invertebrates in general have high efficiencies (30-50%), losing relatively lit- tle energy in respiratory heat. Among the vertebrates, ectotherms (whose body temperature varies accord- ing to environmental temperature; see Chapter 3) have intermediate values for PE (around 10%), while endotherms, which expend considerable energy to maintain a constant temperature, convert only 1% to 5% of assimilated energy at most into production. Microorganisms, including protozoa, tend to have very high PEs, 50% or greater.
Trophic transfer efficiency
One trophic level to the next is simply CE x AE x PE. This represents the percentage of energy (or organic matter)
at one trophic level that is transferred to the next.
Assimilation efficiency (AE)
The percentage of food energy taken into the guts of consumers in a tro- phic level that is assimilated across the gut wall and becomes available for incorporation into growth or to do work. The remainder is lost as feces and enters the decomposer system. It is harder for us to ascribe an assimilation efficiency to microorganisms, in which food does not pass through a gut and feces are not pro- duced. Bacteria and fungi digest dead organic matter externally and, between them, typically absorb almost all the product: they are often said to have AEs of 100%. AEs are typically low for terrestrial herbivores, detritivores, and microbivores (20-50%), somewhat higher for aquatic herbivores, and high for carnivores (around 80% and sometimes higher). The way plants allocate production to roots, wood, leaves, seeds, and fruits also influences their usefulness to herbivores. Seeds and fruits may be assimilated with efficiencies as high as 60-70% and leaves with about 50% efficiency, while the AE for wood may be as low as 15%.
Immobilization
Occurs when
an inorganic element is incorporated into organic form, often during primary production, for example, when carbon dioxide becomes incorporated into a plant’s carbohydrates.
Mineralization
Chemical nutrients—the conversion of elements from organic back to an inorganic form.
Decomposition
The gradual disintegration of dead organic matter (dead bodies, shed parts of bodies, feces) and is brought about by both physical and biological agencies.
Microbivore
A group of animals that
operate alongside the detritivores and can be difficult to distinguish from them.
Shredder
Detritivores that feed on coarse particulate
organic matter, such as tree leaves fallen into a river; these animals fragment the material into finer particles.
Collecter-filterer
Such as larvae of blackflies in rivers, consume the fine particulate organic matter that otherwise would be carried downstream.
Cellulase
Enzymes that break down the cellulose found in plant cell walls into simple sugars that can serve as the raw materials for biofuels, as well as many of the biobased chemicals, plastics, and other materials
Nitrogen cycle
The continuing transformation of nitrogen including assimilation into biomass and mineralization back to ammonium.
Nitrogen fixation
Any natural or industrial process that causes free nitrogen
(De)Nitrification
Denitrification occurs in environments largely devoid of oxygen and is a type of respiration in which the bacteria use nitrate instead of oxygen as an electron acceptor.
Closed system
Ecosystems that do not rely on matter exchange with any part outside the system.
Open system
One in which energy can be transferred between the system and its surroundings.
Weathering
The breaking down or dissolving of rocks and minerals on the surface of the Earth
Deposistion
The net flux of materials from the atmosphere to the ecosystem.
