ECOSYSTEMS DIFFER IN PRODUCTIVITY

Food webs, food chains, pyramids – you can also look at ecosystems through their productivity.

Productivity is the rate at which chemical energy is produced in an ecosystem – expressed as ‘gram of organic matter per square metre per year’

Primary Productivity of Ecosytems

1.Gross primary productivity (GPP) is the rate at which an ecosystem's producers convert solar energy into chemical energy as biomass.

2. Net primary productivity (NPP) is the rate at which energy for use by consumers is stored in new biomass.

NPP = GPP – R [rate at which producers use biomass]

Productivity of ecosystems

Generally ecosystems with the highest net productivity are those with the greatest accumulated producer biomass

The higher the net primary production of an ecosystem, the more food is available for consumer organisms and the greater the biomass of consumers living in that ecosystem.

More producer biomass

More photosynthe

sis

More chemical energy

stored in organic matter

1. Why does a desert ecosystem have a lower productivity than a tropical rainforest?

2. What affects do temperature and hours of sunlight have on productivity?

3. List some limiting factors for ecosystems?

4. Explain why Australia does not have rich fishing grounds near its coast.

1. If light is needed for photosynthesis, but does not penetrate to the depths of the ocean, how does a consumer in ocean darkness feed?

2. Explain how producers can exist in the dark depths of the ocean.

3. Explain the difference between photosynthetic organisms and chemosynthetic organisms.

4. What is the energy source for photosynthetic organisms? What is the waste product?

5. What is the energy source for chemosynthetic organisms? What is the waste product?

Photosynthesis: use of chlorophyll. Energy storing process.

6 CO2 + 6 H2O + solar energy C6H12O6 + 6 O2 Cellular Respiration:

Aerobic Respiration: energy releasing process. C6H12O6 + 6 O2 6CO2 + 6 H2O + energy (ATP)

Anaerobic Respiration Ex. Fermentation: energy releasing process used

by yeast and bacteria