Pyramids

Numbers, Biomass, & Productivity

FOOD CHAINS AND PYRAMIDS

Pyramid diagrams give information about the organisms in a food chain: numbers of organisms biomass of organisms energy stored in organisms productivity of organisms

Pyramid diagrams

are drawn to scale the width of each rectangle is

proportional to: the number of organisms per square

meter or the biomass in grams per square

meter or the productivity in joules per square

meter per month/year

Pyramid of Numbers The information collected for each trophic

level is the total number of organisms in the area, which depends on: the size of individual organisms the standing crop at the trophic level

Problem is each organism is counted equally. 1000 kg tree = 1 gram grass plant

Units = organisms Number pyramid diagrams may be:

upright pyramids inverted pyramids

Pyramid of Biomass Takes the total biomass of all organisms

at each trophic level in the area , and depends on: the energy available at each trophic level the standing crop at each trophic level

Problem it is a measure in one instant of time

Unit = grams Biomass pyramid diagrams may be:

upright pyramids inverted pyramids

Pyramid of Productivity These show productivity of organisms at

different trophic levels, which depends on: the energy available from the previous

trophic level the efficiency of the organisms

Unit = joules Designed to eliminate the inverted

pyramid