Transcript PYRAMIDS • Pyramid diagrams give information about the organisms in a food chain:

PYRAMIDS
• Pyramid diagrams give information about
the organisms in a food chain:
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–
numbers of organisms
biomass of organisms
energy stored in organisms
productivity of organisms
• Taken from K:\General Education\IB\Science\Environmental
ystems\ecosystems\pyramids.ppt
PYRAMIDS OF BIOMASS
• These show the total biomass of
organisms at different trophic levels,
which depends on:
– the energy available at each trophic level
– the standing crop at each trophic level
• Biomass pyramid diagrams may be:
– upright pyramids
– inverted pyramids
How can a pyramid of
biomass be inverted?
• Pyramids of biomass measure standing crop at a
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particular moment in time
If you collected the cuttings from a garden lawn,
mown twice a week during the summer, it would make
a huge pile of biomass
But just after cutting, the biomass stored in the lawn
would be quite small
Exchange your lawn mower for a rabbit and you can
see how an inverted biomass pyramid could be
produced
if you measured biomass over the whole summer for
lawn and rabbit, the pyramid would look quite different
PYRAMIDS 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
Productivity pyramid diagrams are always:
– upright pyramids
Now try this:
• You will need graph paper, pencil, ruler
• Draw a pyramid of numbers and a pyramid of
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biomass for each ecosystem
Remember to include the scale and units
Explain why pyramids of number may be upright
or inverted
Are all the pyramids of biomass you have drawn
upright?
Some extra data for
the English Channel:
Organism
phytoplankton
Biomass-dry
mass in gm-2
4.0
zooplankton
21.0
Draw a pyramid of biomass for this data
What type of pyramid is it?
Explain how this is possible,
remembering the lawn and the rabbit.
Some extra data for a pool called Silver
Springs in Florida
trophic level
net
production
top carnivores
respiration
63
25
carnivores
1321
280
herbivores
6178
7900
primary
producers
36922
50060
Productivity is in kJ m-2yr-1
 Draw a pyramid of productivity for this data
 Explain why pyramids of productivity must always be
upright and cannot be inverted