1
Photosynthesis – Inputs
carbon dioxide, water, chlorophyll certain visible wavelengths of light TO PRODUCE – organic matter oxygen

2
Photosynthesis – energy transformation
transformation of light energy into the chemical energy of organic matter

3
Respiration – Inputs organic matter oxygen TO PRODUCE Carbon dioxide
Water WITHOUT Oxygen carbon dioxide other waste products are formed

4
Respiration – Outputs Energy is released in a form available for use by living organisms, but is ultimately lost as heat.

5
Primary Productivity What do “producers” gain?
Energy-rich organic compounds from inorganic materials through photo- and chemosynthesis These energy rich compounds can be used in producing more of themselves either through growth or reproduction Production = the incorporation of energy and materials into the bodies of organisms

6
primary productivity “the quantity of organic material produced, or solar energy fixed, by photosynthesis in green plants per unit time” (IB definition) Rate at which autotrophs synthesize new biomass

7
gross primary productivity (GPP)
Total amount of organic material fixed by autotrophs Result of photosynthesis (or chemosynthesis) CO2 + H20 + light energy glucose + O2

8
net primary productivity (NPP)
Rate of production of biomass potentially available to consumers (herbivores) Not all of the total productivity (energy) goes into making biomass (growth and reproduction) Some productivity is used in the autotroph’s own life processes (respiration) and this energy is ultimately lost as heat So, NPP = GPP – R

9
Calculating/Measuring Primary Productivity
Productivity Review Calculating/Measuring Primary Productivity

10
The Formula NPP = GPP – respiration
Gain in energy or biomass per unit time AFTER respiratory losses GPP less the biomass or energy used by autotrophs in respiration Expressed as Energy per unit area per unit time e.g. J/m2/yr Biomass added per unit area per unit time e.g. g/m2/yr

11
Light-Dark Bottle Technique
Measure O2 production in light and dark bottles Light bottle: photosynthesis and respiration Dark bottle: respiration only Determine GPP = Light – Dark NPP = Light – Initial Respiration= Initial – Dark

12
Measuring Primary Productivity
Harvest method – measure biomass change over time and express as biomass per unit area per unit time Destructive! CO2 assimilation – measure CO2 uptake in photosynthesis and release by respiration Assume any CO2 removed is incorporated into organic material by photosynthesis Use dark bottle to measure respiration in absence of photosynthesis to get GPP CO2 is difficult to measure in aquatic systems

13
Factors that Affect Primary Productivity
Solar radiation: quality (type) of light quantity of light productivity (to a point when too much light will inhibit photosynthesis) Temperature: temp. Þ productivity (to a point when high temperatures can denature enzymes) CO2: CO2 productivity (since CO2 is an input) H2O: H2O productivity (again since H2O is an input)

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

Similar presentations