ECOLOGICAL PYRAMIDS

http://www.envf.port.ac.uk/geog/teaching/environ/sect2-3c.htm
http://resources.edb.gov.hk/biology/english/images/environment/pyramid.gif


It allows us to compare the tropic levels in a food chain. There are three types.
Pyramids of numbers
This allows us to compare the number of organisms present in each trophic level at a particular time.

In this pyramid, all the numbers at each trophic level are counted regardless of size and stage development.
http://www.sturgeon.ab.ca/rw/Pyramids/pyrakind.htm







Pyramid of biomass

This allows us to compare the mass of organisms present in each trophic level at a particular time

The pyramid of biomass is constructed based on the dry mass of organisms in each trophic level at any one time. This is called the standing mass of organisms.
The unit of biomass is dry weight of organic matter( per square metre)

pyramid of energy

The total energy at various trophies levels of a food chain represented in a pyramid is called a pyramid of energy.

This is constructed based on total energy level in each trophic level over a certain period of time . down a food chain as energy is transferred from one trophic level to the next, energy is loss. Which is why a this pyramid is always broad at the base and narrow toward the top .


http://resources.edb.gov.hk/biology/english/images/environment/pyramid.gif