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2.5.5 .7


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2.5.5 .7

  1. 1. 2.5.5-.7 Productivity 5/11/2013 Author-Guru IB/ESS 1
  2. 2. • PRODUCTIVITY is production per unit time. energy per unit area per unit time (J m-2 yr-1) Or biomass added per unit area per unit time (g m-2 yr-1) • PRODUCTION is the incorporation of energy and materials into the bodies of organisms (biomass). • BIOMASS is the mass of organic material in organisms of ecosystems. • Usually expressed per unit area. • Standing crop = ecosystem biomass. 5/11/2013 Author-Guru IB/ESS 2
  3. 3. GROSS PRODUCTIVITY (GP) • is the total gain in energy or biomass per unit time. • Could be through photosynthesis or absorption in consumers. 5/11/2013 Author-Guru IB/ESS 3
  4. 4. NET PRODUCTIVITY (NP) • is the gain in energy or biomass per unit time remaining after allowing for respiratory loss. • Organisms use some of the energy they capture to keep themselves growing and alive (metabolism). • The energy used by organisms for essential tasks is called RESPIRATORY ENERGY, and eventually it is released to the environment as heat. 5/11/2013 Author-Guru IB/ESS 4
  5. 5. NP = GP – respiration (for both producers and consumers) When energy is released from ATP it is lost as heat. (2nd Law of Thermodynamics) 5/11/2013 Author-Guru IB/ESS 5
  6. 6. GROSS PRIMARY PRODUCTIVITY (GPP) • is the quantity of matter produced, or solar energy fixed, by photosynthesis in green plants • measured per unit area per unit time. [Chemosynthesis and non-green plant autotrophs too] 5/11/2013 Author-Guru IB/ESS 6
  7. 7. • Energy enters an ecosystem through sunlight. • Only 2% of the light energy falling on a tree is captured and turned into chemical energy (glucose) by photosynthesis. • The rest is reflected, or just warms up the tree as it is absorbed. 5/11/2013 Author-Guru IB/ESS 7
  8. 8. Net Primary Productivity (NPP) • The quantity of biomass potentially available to consumers in an ecosystem. • It is measured in unit of mass or energy per unit area per unit time. • Plants have to use some of the energy they capture to keep themselves growing and alive (metabolism). NPP = GPP - respiration 5/11/2013 Author-Guru IB/ESS 8
  9. 9. SECONDARY PRODUCTIVITY (SP) • biomass gained by heterotrophic organisms through feeding and absorption. • Not all food eaten is absorbed (assimilated) into an animals body. • Unassimilated food = feces or droppings SP = food eaten – fecal loss 5/11/2013 Author-Guru IB/ESS 9
  10. 10. In a food web you can usually assume that: • The energy input into an organism = GP. • The energy output to the next trophic level = NP. • The difference between GP and NP = R and/or loss to decomposers. 5/11/2013 Author-Guru IB/ESS 10
  11. 11. Measuring Primary Productivity 1. Harvest method - measure biomass and express as biomass per unit area per unit time. 2. CO2 assimilation - measure CO2 uptake in photosynthesis and release by respiration. 3. O2 production - Measure O2 production and consumption. 5/11/2013 Author-Guru IB/ESS 11
  12. 12. Measuring Primary Productivity 4. Radioisotope method - use C14 tracer in photosynthesis. 5. Chlorophyll measurement - assumes a correlation between amount of chlorophyll and rate of photosynthesis. 5/11/2013 Author-Guru IB/ESS 12
  13. 13. What affects productivity? 1. 2. 3. 4. 5. 6. 5/11/2013 Solar radiation Temperature CO2 H2O Nutrients Herbivory Author-Guru IB/ESS 13
  14. 14. Therefore… • The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients. • The most productive ecosystems are those with high temperatures, lots of water, light and nutrients. 5/11/2013 Author-Guru IB/ESS 14
  15. 15. Biome Productivity Estuaries Swamps and marshes Tropical rain forest Temperate forest Northern coniferous forest (taiga) Savanna Agricultural land Woodland and shrubland Temperate grassland Lakes and streams Continental shelf Open ocean Tundra (arctic and alpine) Desert scrub Extreme desert 800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600 Average net primary productivity (kcal/m2/yr) 5/11/2013 Author-Guru IB/ESS 15
  16. 16. Three years of satellite data on the earth’s GP. LAND: high = dark green low = yellow 5/11/2013 OCEAN: high = red IB/ESS blue low = Author-Guru 16
  17. 17. 73% Not used by humans Human use of biomass produced by photosynthesis (NPP). 3% Used directly 8% 5/11/2013 Lost or degraded land 16% Author-Guru Altered by human activity IB/ESS 17