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Food Chains & Food Webs
Most organisms feed on more than
one trophic level and feed on
several different species at each
trophic level.
Biomagnification
Increase in concentration of a
substance throughout the food
chain
http://www.youtube.com/watch?v=E
5P-UoKLxlA
Ecological Pyramids
Instead of
representing
trophic levels in
a food chain, an
ecological
pyramid can be
used.
Ecological Pyramids
This pyramid would represent a food web if different organisms were present together at each level .
For example, a frog and a mouse on level 3 and/or a grasshopper and butterfly on level 2.
Pyramid of Energy
The big numbers represent the trophic levels.
kcal represents
the energy content at that level.
#3-4
Pyramid of Energy
As you go up the pyramid, the energy level
decreases.
Only about 10% of the
energy from the
previous level is
available.
This pyramid is called
an energy pyramid
because it shows the
amount of energy at
each trophic level.#5-7
Pyramid of Numbers
The numbers
pyramid
represents the
total number
of individuals
counted at
each level.
#8
Pyramid of Numbers
To get a number
total for a
population of
organisms, you
have to count
the organisms in
a specific area,
such as an acre
and then
estimate.
#9
Pyramid of Biomass
A biomass pyramid represents an
estimate of the mass of the
population.
To get this
information, you
calculate the mass
of a sample of
organisms and
then estimate.
#10
Ecological Pyramids
A pyramid is often used to represent
feeding relationships because
energy, biomass and the number of
organisms generally decrease as you
move up the food chain.
Ecological Pyramids
This pyramid is different because it shows the producers as being very small.
Something to think about (but not answer yet): How can the producer level be so small and support the trophic levels above it?