Chapter 11 - The Flux of Matter and Energy through Ecosystems Flashcards
What is a standing crop?
It is the bodies of living organisms within a unit area, constituting a standing crop of biomass
ex. trees
What is biomass?
It is the mass of organisms per unit area of ground/water, usually expressed in units of energy (ex. joules/sq. m), and dry organic matter (g/sq. m) or mass of carbon (g of C/sq. m).
Basically mass per area that could include all organisms
What is primary productivity?
It is the rate at which biomass is produced per unit are or volume through photosynthesis and can be expressed in many different units (ex. GPP & NPP).
Rate of biomass production per area per time
What is gross primary productivity (GPP)?
It is the total fixation of energy by photosynthesis, but a portion of this as respiratory heat (R auto)
What is respiratory heat (R auto)?
It is a portion of the GPP that is respired away by primary producers and is lost as respiratory heat
What is net primary productivity (NPP)?
It is GPP-R auto and represents the actual rate of new biomass production available for consumption by heterotrophs
What is secondary productivity?
It is the rate of biomass production by heterotrophs
What is net ecosystem productivity (NEP)?
It is the difference between GPP and the respiration of all organisms in an ecosystem (R total). It measures the net rate of accumulation/loss of OM, energy, or organic carbon from an ecosystem and is equivalent to NPP-R het (the respiration of heterotrophic organicms)
What is a live consumer system?
It is when a portion of primary production is consumed by herbivores, which are then consumed by carnivores
What is a decomposer system?
It is the other portion of NPP not eaten by herbivores but by detritivores and decomposers.
What are the 2 groups of organisms responsible for decomposition of dead OM (aka detritus)?
- Decomposers: bacteria and fungi
2. Detritivores: animals that consume dead OM
What are the necessary (and limiting) factors of primary production?
- sunlight, CO2, H2O, and nutrients
- temp does have an influence on the rate of PP
What is Liebig’s Law of the Minimum?
It states that the growth of a plant is limited primarily by one nutrient that is in relatively short supply (usually N or P). The nutrient that is the most important but least available will control NPP.
ex. tropics are more P-limited (old, weathered soil) and the boreal is more N-limited (young, nutrient-lacking soil)
What is colimitation?
It is when both N and P are limiting to PP.
ex. occurs in temperate forests
What are the most limiting factors in aquatic PP?
- nutrients (more responsive to limiting nutrients) and light (comes from phytoplankton)
- there is higher nutrient limitation b/c fewer nutrients are based on biomass
What is eutrophication?
It is the process of excess nutrient enrichment and can lead to algal blooms, which are very damaging and deplete ecosystems of oxygen
What is a positive feedback loop?
It is when one factor influences another factor and continues until it can no longer.
ex. high growth leads to high pop size which further increases growth rate and is only constrained by P
Proportions of NPP flowing along each possible energy pathway depends on:
Transfer efficiencies
What is consumption efficiency (CE)?
It is the % of total productivity that is available at one trophic level that is consumed by the above trophic level
What is assimilation efficiency (AE)?
It is the % of food energy taken into the guts of the consumers in that trophic level that is assimilated across the gut wall and becomes available for incorporation into or to do other work
What is production efficiency (PE)?
It is the % of assimilated energy incorporated into new biomass; the remainder is entirely lost to the community as respiratory heat
What is the overall trophic transfer efficiency?
It is CEAEPE and represents the % of energy or OM at one trophic level that is transferred to the next. Roughly 10% energy passed onto each level.
Look at drawing and efficiencies in slides!
What is immobilization?
It occurs when an inorganic element is incorporated into organic form (often during PP)
ex. CO2 incorporated into plants carbohydrates
What is decomposition?
It is the gradual disintegration of dead OM (bodies, feces, etc.) and is brought about by both physical and biological agencies. It includes the release of energy and mineralization of chemical nutrients
What is mineralization?
It is the conversion of elements from organic back to inorganic form
What are microbivores?
They are a group of animals that operates alongside detritivores and can be difficult to distinguish from them as they are minute animals that specialize at feeding on bacteria/fungi, but are able to exclude detritus from their guts
What are shredders?
They are detritivores that feed on coarse particulate OM, such as tree leaves fallen into a river, because they fragment material into finer particles
What are collector-filterers?
They consume fine particulate OM that would otherwise be carried downstream.
ex. river black fly larvae
What do detritivores rely on to break down cellulose?
They rely on the production of cellulase enzymes by associated bacteria/fungi and protozoa
What is the nitrogen cycle?
It is the continuing transformations of nitrogen, including biomass assimilation and ammonium mineralization
What is nitrogen fixation?
It often occurs for plants through symbionts that convert N2 into NH4 (a useable form)
What is denitrification?
It is when other bacteria are constantly converting nitrate into molecular N2 and mostly occurs in anaerobic environments
What is nitrification?
It is when other bacteria convert ammonium to nitrate (for autotrophs to fix CO2)
How can ecosystems be characterized by their openness/closedness?
By comparing their exchange of limiting nutrients across a border with the rate of recycling in an ecosystem.
ex. subtropical gyre is tightly closed because lots of recycling occurs and very few new N & P atoms enter surface water (assimilation by phytoplankton during NPP)
ex 2. heavily fertilized agricultural field has high rates of water exchange with adjacent estuaries, so the external supply of N may exceed the rate of recycling, making it open
What is weathering?
It is when the parent bedrock or soil is broken down over time by the weather conditions, which is often the main nutrient source in many terrestrial ecosystems (taken up by roots)
What is atmospheric deposition?
It is the net flux of materials from the atmosphere to an ecosystem. It is a major input source and is substantial in ecosystems with old weathered soils
What is the first law of thermodynamics?
Conservation of matter & energy: Energy can be transformed but not created nor destroyed
What is the second law of thermodynamics?
Entropy: Entropy is random, unavailable energy and disorder is always increasing
Converting energy causes an entropy tax b/c nothing is 100% efficient
