IB Environmental Systems and Societies/Function

2.5 Function
2.5.1 Explain the role of producers, consumers and decomposers in the ecosystem.
 * Producers: Organisms that use sunlight energy to create food are called Photoautotrophs
 * Consumers: They eat other organisms to obtain energy. For example, herbivores will eat the plants, then the herbivores are eaten by carnivores or omnivores
 * Decomposers: Obtain energy from breakdown of dead organic matter. They are key to the nitrogen cycle. They convert ammonia from decomposing organisms and excretory waste into nitrites and ultimately into nitrates. Plants then take nitrates through their Root systems

2.5.2 Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations.
 * Photosynthesis (CO2 + H2O --> C6H12O6 + O2)

Inputs: Carbon Dioxide & Water Outputs: Glucose & Oxygen Transformations: Producers transform light energy (from the sun) into chemical energy


 * Respiration (C6H12O6 + O2 --> CO2 + H2O + Heat)

Inputs: Glucose & Oxygen Outputs: Carbon Dioxide & Water Transformations: Chemical Energy turns into Heat

2.5.3 Describe and explain the transfer and transformation of energy as it flows through an ecosystem.

- Explain pathways of incoming solar radiation incident on the ecosystem including:
 * loss of radiation through reflection and absorption
 * conversion of light to chemical energy
 * loss of chemical energy from one trophic level to another
 * efficiencies of transfer
 * overall conversion of light to heat energy by an ecosystem
 * re-radiation of heat energy to the atmosphere.

- Construct and analyse simple energy-flow diagrams illustrating the movement of energy through ecosystems, including the productivity of the various trophic levels.
 * Storages = Boxes
 * Flows of energy or productivity = Arrows

2.5.4 Describe and explain the transfer and transformation of materials as they cycle within an ecosystem.


 * Processes involving the transfer and transformation of carbon, nitrogen, and water as they cycle within an ecosystem should be described, and the conversion of organic and inorganic storage noted where appropriate. Construct and analyse flow diagrams of these cycles

2.5.5 Define the terms Gross productivity, net productivity, primary productivity and secondary productivity.


 * Gross Productivity: The total gain in energy or biomass per unit area per unit time, which could be through photosynthesis in primary producers or absorption in consumers.
 * Net Productivity: The gain in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R). Other metabolic losses may take place, but these may be ignored when calculating and defining net productivity for the purpose of this course.
 * Primary Productivity: The gain by producers in energy or biomass per unit area per unit time. This term could refer to either gross or net primary productivity.
 * Secondary Productivity: The biomass gained by heterotrophic organisms, through feeding and absorption, measured in units of mass or energy per unit area per unit time.

Productivity is production per unit time.

2.5.6 Define the terms and calculate the values of both gross primary productivity (GPP) and net primary productivity (NPP) from given data.


 * Gross Primary Productivity: The total gain in energy or biomass per unit area per unit time fixed by photosynthesis in green plants.
 * Net Primary Productivity: The gain by producers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R). This is potentially available to consumers in an ecosystem.

Use the equation NPP = GPP – R, where R = respiratory loss

2.5.7 Define the terms and calculate the values of both gross secondary productivity (GSP) and net secondary productivity (NSP) from given data.


 * Gross Secondary Productivity: The total gain by consumers in energy or biomass per unit area per unit time through absorption.
 * Net Secondary Productivity: The gain by consumers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R).

Use the equation NSP = GSP – R, where R = respiratory loss Use the equation GSP = food eaten – fecal loss