PYRAMID OF PRODUCTIVITY

Pyramids of numbers and mass

Pyramids of numbers:

We can use pyramids of numbers to represent the number of individuals in an ecosystem feeding at each trophic level.
For instance:
external image numbers.gif

The pyramid shows that a large number of producers support a smaller number of primary consumers which in turn provides food for and even smaller number of secondary consumers and so on.

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PROBLEMS WITH PYRAMID OF NUMBERS
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external image pyramid-oak-wood.jpg

  • We see immidiately that in this is no longer a pyramid . It has the shape of an inverted pyramid .
  • In this inverted pyramid an oak tree can't suppport many primary consumers.
  • It does not seem logical that 1 tiny organism is represented in the same way as 1 relatively massive organism.

THE SOLUTION
use a pyramid of Biomass.

BIOMASS: is the total mass of organic(living) material , once water is removed.
external image 300px-BioPyramid.png

In the inverted pyramid of numbers it becomes a regular pyramid of biomass.
Units of biomass are typically kilograms per square meter. (kg/m² ) or kgm²