Flows of Energy and Matter (2.3)
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Notes & ReviewNotes: Topics 2.2, 2.3, 1.2, 1.3jeopardy Review (2.2, 2.3, 1.2, 1.3) |
Energy Pathways through an ecosystem
Energy that enters an ecosystem begins with the Sun. The amount of energy produced by the sun that reaches the atmosphere of earth is referred to as the solar constant (1,400 J s-1 m-2). However, not all of the energy reaches the producers on the earths surface either. Reasons why it does not reach the surface include:
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Productivity
Productivity: the conversion of energy into biomass over a given time period
Environmental Factors affecting Plant Productivity Biomass and Productivity Biomass and production |
■Biomass= living mass of (an) organism(s)
Why is productivity important?
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Gross Productivity
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Net Productivity
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primary Productivity
Primary Productivity (PP): energy converted by producers into chemical energy
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Secondary Productivity
In general:
Carnivores:
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Secondary productivity deals with consumers. It is overall harder to measure and therefore not often used as a measurement of productivity.
Nutrients that are assimilated (absorbed through the digestive tract) can be incorporated into the animals biomass. Once absorbed, the following things can occur:
The total amount of food ingested included what is removed from the body is Gross Secondary Productivity (GSP).
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productivity and Farming Practices
How efficient is productivity assimilation? In general not the efficient. To determine this we need to things:
- The proportion of NPP from one trophic level that is assimilated into the next trophic level
- How much of the assimilated material is turned into biomass vs being respired.
- How much of the grass an animal eats is assimilated into the body of the animal? (This helps the farmer decide how many animals their land can sustain)
- How much of what is assimilated is used for productivity (converted into biomass/ meat)? (Helps the farmer determine profits)
- Maximizing either or both of these can be an advantage to the farm.
Trophic Levels energy transfers are inefficient. This is due to a variety of reasons.
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Every living things or population has a quantitative amount of energy needed to survive = Energy budget.
- we can measure the amount of energy entering and staying within the animal and then leaving.
Energy Subsidy = the additional energy a farm is required to put into the system. Energy can come in the form of:
Higher densities within cities forced higher and more efficient agricultural practices. These forced greater energy subsidies to be added to the system. |
Economically, farms are often looked at in terms of Energy: Yield Ratios = Energy in and energy out in the form of food.
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Carbon CYCLES
Nutrient cycles can be broken into storage and flow diagrams much like any system. Storages will be in red and flows will be in blue
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Human interference and Consequences
Most scientists agree that there is a finite amount of carbon on Earth, we generally know where it goes.
- CO2 is the main culprit in global warming (according to current science)
- Burning forests and fossil fuel combustion release more CO2 in atmosphere adding to global warming and climate change. This is the primary way in which we disrupt the carbon cycle.
- Deforestation for agriculture use is another way we disrupt the cycle. By removing trees that pull CO2 out of the atmosphere and disturb soil which acts as a carbon sink we release (and keep) more CO2 in the atmosphere.
Nitrogen Cycle
Nutrient cycles can be broken into storage and flow diagrams much like any system. Storages will be in red and flows will be in blue
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Human interference and Consequences
Humans disrupt the nitrogen cycle in a few different ways:
- Release of more nitric oxides (NOx) into atmosphere through cars
- This is one of the main causes of photochemical smog
- The industrial Haber process uses nitrogen fixation to create fertilizers.
- The addition of fertilizers add more NOx in the soil causing nitrogen rich soils crowding out plant life.
- Run-off from farms and industry add NOx to water ways creating dead zones, eutrophication, and other issues within the water ways.
- Waterlogged soils also mean bacteria vital to the nitrogen cycle often are unable to breakdown the nitrogen to keep the process going.
Energy Flow Diagrams
Like nutrient cycles, energy cycles/ food webs can be broken into storage and flow diagrams much like any system. Storages will be in red and flows will be in blue.
Remember: storages are boxes and flows are labeled on the arrows.
Remember: storages are boxes and flows are labeled on the arrows.
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