Energy in an Ecosystem
Get out your HW and grab your
ecosystems…
Pre Quiz: Get out a pencil and answer the
questions.

If you start with 1000kg of biomass of primary
producers, how much biomass would you have
of…
1.
2.
3.
4.
5.
What is biomass?
Primary Consumers?
Secondary Consumers?
Tertiary Consumers
Why does a biomass diagram form a pyramid?
Where does the Energy come from?
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All the energy in an
ecosystem comes from the
sun.
1 - 2 % of the sun’s energy
that strikes the earth is
absorbed by plants


The rest is absorbed by abiotic
objects or deflected to space
Plants use that energy
through photosynthesis to
produce sugar (glucose)
which can then be converted
to the biomass of the plant.
What is Biomass?
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Biomass – This is
the mass of all
matter at any level
in a food chain
The amount of
biomass in a in each
trophic level of a a
food chain creates a
pyramid (diagram)
when shown
graphically.
Pyramid of Biomass
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How much of the mass
is transferred to the next
level?
*Approximately 10% of
biomass at one level
becomes biomass at the
next level.
What happens to the
other 90 %
*The other 90% is
uneaten, undigested (this
energy is available to
decomposers) or given
off as heat from the
activities of the
organism.
What Causes a
Decrease in Biomass?

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Biomass decreases
with each additional
step upward in a food
chain.
Energy is lost as heat
(and cannot be
reused) in each step of
the food chain
(diagram on next
slide) or as waste.
Which diagram in more accurate?
Primary Productivity

The amount of biomass created by an ecosystem at the
producer level. The rate at which solar energy is converted
to usable energy in the ecosystem.
What is a Pyramid of Numbers?

This is a pyramid showing that a large number of
organisms (see primary productivity) is required at the
base of the food chain (there are exceptions) to support a
small number of organisms at the top.
Answer these questions…

The number of organisms at the highest level
in a food chain is directly related to the
number of levels in the chain. How can more
organisms be supported in an ecosystem?

What is the difference between a pyramid of
biomass and a pyramid of numbers?
Biomass Pyramid Video
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http://www.youtube.com/watch?v=NJplkrliUEg