Transcript Energy Flow: Food Chains and Webs

Energy Flow:
Food Chains
and Webs
Energy Transfer
 Energy
transfers from one
organism to another when
they are consumed and
metabolized.
 Energy can be followed
based on how organism
obtain energy.
 Trophic levels – the position
of an organism in a
sequence of energy transfer
 Trophic levels are depicted
in food chains.
Food Chains and Food Webs
A
food chain is a single pathway of
feeding relationships in an ecosystem
 Draw the following food chain!
 Feeding relationships are much more
complex than a simple food chain. This
complexity is shown through a food web.
 Add on to the chain in a food web!
10% rule
 Every
time energy is
transferred from one
organism to another, not
all of the energy is
passed on. In fact, more
often than only a very
low portion of the energy
is transferred.
 On average, only 10% of
the total energy
consumed in one trophic
level is passed on to the
next level.
 Why?
Biomass
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Because so little of the
energy is transferred from
trophic level to trophic level,
the higher trophic levels can
only support a limited number
of organisms.
This is because they must
consumer a greater number
of organisms to reach the
amount of energy they need
to survive.
This is why an ecosystem will
have less carnivores than
herbivores. For example in
Africa there about 1000
herbivores for every lion.
Biological Magnification
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The low energy transfer in
each trophic level can
lead to some serious
consequences in the
higher trophic levels.
Biological magnification is
the increase of a
substance in food chains
or webs due to the low
transfer of energy which
leads to the need for
consumption of a greater
number of organisms at
the high trophic levels.
Food chains and
webs
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Create a food chain
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Make it a food web
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Use 4 organisms and the sun
Use arrows in one color to show the flow of energy
Label each organism with its trophic level
Show how much energy is in each level
Label them with what type of producer or consumer they
are (herbivore, carnivore, etc)
Add 6 more organisms to your chain to make it a web
Use arrows in a second color to show the flow of energy
Label them with what type of producer or consumer they
are (herbivore, carnivore, etc)
Explain the 10% rule and biological magnification in
your own words on the back