Transcript Pyramids of Numbers and Biomass

Pyramids of Numbers
and Biomass
Pyramids Of Numbers
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A pyramid of number is a
diagram showing the
amount of energy lost at
each level when an
organism eat another
organism. There are 4
levels the, producers, the
primary consumers, the
secondary consumers and
the tertiary consumers.
To draw a pyramid of numbers, the number of
organisms must be counted for each feeding level.
This is done for a given area. Once you have
gathered your information you must draw the
chart. You use horizontal blocks representing the
number of organism drawn to scale on graph
paper. The block representing the food producer is
placed at the bottom of the diagram. You then
place other blocks representing the other feeding
levels to give a pyramid shape.
Problems With Numbers

There is a problem however
with the way a number pyramid
works. If you were to do a
number pyramid and you
wanted to use oak leaves as the
producer, instead of counting all
the oak leaves on the tree you
might decide to use the entire
oak tree. This then means that
that one oak tree counts as the
same as one caterpillar, despite
the size difference. This affect
can produce misleading
diagrams like the one shown
here. Therefore it is better to
construct a pyramid of biomass.
Pyramids of Biomass

Biomass is a measure
of the mass of living
tissue in an organism .
A pyramid of biomass
gives a better diagram
than the a pyramid of
numbers because it
shows the loss of mass
from producers to
consumers in a food
chain.
Energy Lost In A Food Chain
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There is two reasons as to why energy is lost in a food
chain,
Firstly an organism use up energy to build it’s body. This
may include parts such as skin and horns, witch when
eaten by another consumer turns out to have very little
nutritional value. Therefore these parts are tended to be left
uneaten. As a result, that energy is not being eaten and
therefore is lost from the food chain.
Secondly, most of the energy gained by the consumer is
used for moving about and for keeping warm. Much
energy is then lost as heat and only about 10 per-cent of
energy that is taken in by organism is taken in.
This Production Was Brought To
You By…
Lizzie
Ward-Smith