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Ecosystems (Energy and Nutrients)
Terms in this set (17)
How does energy and nutrients flow/cycle through ecosystems?
Organisms capture energy, and transform it to biomass and/or heat.
energy is passed through "levels" in the ecosystem. Various routes through which energy can pass.
Where does energy go and what role do primary producers play? What is primary production? NPP? GPP?
Ultimately, all is lost as heat, along the way, it may reside in energy rich compounds. Primary producers make biological tissues using inorganic molecules (own food).
NPP = organic biomass available for non-photosynthetic organisms to eat. Represents the amount of energy available to consumers and decomposers for growth and reproduction
GPP = the total amount of photosynthesis in a given area in a given time.
How do food webs and food chains differ? Why is it useful to describe ecosystems based on feeding relationships and why are primary producers particularly important?
Food Chain = a straight line sequence of who eats whom in an ecosystem
Food Webs = a diagram of all the food chains with their interconnections within an ecosystem.
Most food chains in an ecosystem are interconnected and primary producers make their own food from the sun resulting in them carrying 100% of the base energy for each ecosystem.
Identify the different trophic levels (e.g., primary producer, primary decomposer, primary/secondary/tertiary consumer) and what each of these level eat (e.g., herbivore eats plant tissue, carnivore eats...decomposer eats...)
Primary producers(1000)>Primary Consumers and Decomposers (200, 20% energy transfer)>Secondary Consumers (30, 15% energy transfer)>Tertiary Consumers (3, 10%)
How does grazing vs. detrital (decomposer based) food chains differ? Which captures most of the available NPP and why?
Grazing food chain is composed of network of herbivores (primary consumers) and the organisms that eat herbivores (secondary consumers).
Decomposer food chain is made up of species that eat the dead remains of organisms.
Most primary production goes into detrital food webs (bacteria, archaea, fungi are all decomposers that consume detritus).
Trophic pyramids are used to illustrate the efficiency of energy transfer from one trophic level to the next. In general, we use the 10% rule to describe how energy transfers, describe this rule.
Efficiency varies widely, in general efficiency of biomass transferred between trophic levels is about 10%
What the 10% rule does not take into account is that efficiency of energy transfer varies widely among organisms and systems. What are some factors that reduce trophic transfer efficiency? Certain fish and cows are both primary consumers (herbivores). Which is more efficient (which gets more energy for growth/reproduction) and why?
-Not all production at one trophic level is eaten at the next.
-Not all material is eaten can be digested and assimilated.
-Energy that is used for metabolism is unavailable for growth and reproduction.
-Heat loss in any chemical rxn.
-Basic maintenance (respiration).
Fish are more efficient because body temperature is higher for cows than fish and because cows expend ERG heating bodies rather than biomass
What is biomagnification and how does it relate to food chains? Use an example to illustrate your understanding... describe the trophic pathway and the consequences. Specifically, describe how concentrations of pollutants accumulate as you move up the chain?
Biomagnification = substance increases in concentration as they transfer to different trophic levels.
Methyl mercury levels in fish
(EPA advice for consumptions)
Mercury Mine->Methylmercury flows down through streams->Krill eat it->Salmon Pollock oyster eat krill->Trout Tuna eat Salmon Pollock Oyster->Shark Pike Albacore Halibut eat Trout Tuna
Krill & Salmon Pollock Oyster (unlimited)
Trout Tuna (eat a few times per week)
Shark Pike (Eat only a few times per month)
Trophic cascades are seen in terrestrial and aquatic systems. What is a trophic cascade and be able to illustrate with an example.
When effects extend through additional trophic levels.
Wolf re-introduction into park
In general, trophic cascades are driven by top-down control but sometimes can be driven by bottom-up. What is the difference between top-down and bottom-up control and give an example of each of these regulation factors.
Top-Down Control = Consumer limits a prey population (e.g., Sea star and mussels, Orca and sea otter, Wolves and elk)
-Consumers depress trophic levels on which they feed and regulate populations
Bottom-Up Control = Availability of food and/or habitat (resources) limit or regulates populations
Patterns in NPP = which biomes show the highest and lowest NPP in terrestrial vs. aquatic ecosystems and why? What limits NPP in terrestrial vs aquatic ecosytems?
High: Tropic, wet forests, wetlands, estuaries and coral reefs.
Low: Tropical forests, wetlands, estuaries and coral reefs.
Few nutrients productivity in aquatic environments limited by nutrients.
How do nutrients cycle along coastlines vs. the open ocean?
Coastlines: Nutrients in terrestrial run-off, nutrients in up-welled water from deep ocean
Open ocean: They drift down; nutrients are tied up in organisms, if they are not eaten, they sink.
The rate of nutrient cycling in terrestrial environments is influenced by what factors? Thinking about two extreme biomes (Tropical forest vs. Boreal Forests) predict the rate of decomposition relative to one another and describe what factors influence these rates.
Decomposition of detritus limits the overall rate at which nutrients move through an ecosystem (i.e. until decomposition occurs, nutrients stay tied up in intact tissues).
Decomposition rate is influenced by:
1. Abiotic factors (e.g. oxygen availability, temperature, and precipitation).
2. The quality of the detritus as a nutrient source for decomposers.
Boreal Forests - organic matter builds up because cold and wet conditions limit the metabolic rates of decomposers.
Topic forests - decomposers keep pace with detrital inputs as a result of high temperatures and precipitation.
How are nutrients lost or gained? How can human activities accelerate nutrient loss?
Lost: Nutrients leave an ecosystem whenever biomass leaves.
-Herbivore eats a plant and moves out of the ecosystem before excreting the nutrients or dying
-Nutrients leave ecosystems when flowing water or wind removes particles or inorganic ions and deposits them somewhere else
-released as rocks weather
-Blow n in on soil particles or arrive as solutes in streams
-Nitrogen is added when nitrogen-fixing bacteria convert molecular nitrogen (N2) in the atmosphere to usable nitrogen in ammonium or nitrate ions.
Deforestation, agricultural practices, habitat conversion
Nutrient cycles consist of pools (reservoirs) and fluxes that illustrate storage and movement of organic and inorganic material. What are the major pools and fluxes in the carbon cycle.
1) Fossil Fuels (5-10,000)
2) Rock (limestone, 1,000,000)
3) Oceans (dCO2, 40,000)
1) Oceans (about 90/year, net 1.5 uptake)
2) Photosynthesis (110/year, 3.0 net uptake)
*Atmosphere is very sensitive to changes in flux from large pools
How are humans impacting the carbon cycle? Think about both how we liberate it from pools (fossil fuels) and reduce our carbon sinks (deforestation). We talked about several greenhouse gasses, what are they? CH4 is particularly of concern, how do humans add methane.
Human activity accounts for about 7.9 Gt/year of carbon being added to atmosphere.
-2Gt fixed by photosynthesis
-2 Gt fixed by physical and chemical processes in Oceans
-remaining 3.9 Gt is added to atmosphere each year
Liberation of Carbon pools:
-combustion of living plant material fossil fuels
-dramatically increases rate of carbon cycling
CH4 = a potent greenhou gas (20x CO2)
Responsible for about 20% of greenhouse effects. Added from fossil fuels, methanogenesis in agriculture (rice, cows, etc)
Which countries are most responsible carbon additions to the atmosphere? Do you think these countries have an ethical obligation to mitigate affects for other countries?
U.S. (25.0), Canada (24.3), South Korea (19.2), Norway(17.1), Australia (15.8).Yes, cause of the problem.
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