Energy in the Ecosystem
All the energy in an ecosystem comes from the sun as light.
- 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- contains energy
- 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 1) uneaten, 2) undigested (this energy
is available to decomposers) or given off as 3) 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) are
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.
- More organisms can be supported if the food chain is
shortened – skip levels (more biomass available)