Energy in the Ecosystem
All the energy in an ecosystem comes from the sun.
- 1 - 2 % of the sun’s energy that strikes the earth is
absorbed by plants
- Plants use that energy through photosynthesis to
produce sugar (glucose) which can then be converted to
the biomass of the plant.
Biomass – This is the mass of all matter at any level in a
food chain
- The amount of biomass in a food chain creates a
pyramid (diagram)
- Approximately 10% of biomass at one level becomes
biomass at the next level.
- The other 90% is uneaten, undigested (this energy is
available to decomposers) or given off as heat from the
activities of the organism.
* Biomass decreases with each additional step in a food
chain
* Energy is lost as heat (and cannot be reused) in each
step of the food chain
Number Pyramid – This is a pyramid showing that a large
number of organisms (see primary productivity) is required
at the base of the food chain (there are exceptions) to
support a small number of organisms at the top.
Primary productivity – The amount of biomass produced by
plants in an ecosystem.
- The number of organisms at the highest level in a food
chain is directly related to the number of levels in the
chain.
- More organisms can be supported if the food chain is
shortened (more biomass available)