April 26, 2017
 Journal: How are photosynthesis and
cellular respiration related to each
other?
AP Biology
Energy Transfer in Ecosystems
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Ecosystem inputs
energy flows
through ecosystems
nutrients cycle
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nutrients
can only
cycle
biosphere
inputs
 energy
 nutrients
Energy flows through ecosystems
sun
secondary
consumers
(carnivores)
primary consumers
(herbivores)
producers (plants)
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loss of
energy
loss of
energy
Food chains
 Trophic levels: a position an
Level 4
Tertiary consumer
top carnivore
3
organism occupies in a food LevelSecondary
consumer
chain
 Food chains show feeding
carnivore
relationships
Level 2
Primary consumer
 start with energy from
heterotrophs
the sun which is captured by
herbivore
plants
1
 1st level of all food chainsLevel
Producer
 food chains usually go
up only 4 or 5 levels
autotrophs
 all levels connect to
decomposers
Decomposers
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sun
Bacteria
Fungi
sun
The Cost of Living
 Organisms use energy just by being alive.
Only some of this energy can be passed
on to the next level of the food chain.
17%
growth
only this energy
moves on to the
next level in
the food chain
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energy lost to
daily living
33%
Changing your
food into
usable energy
50%
waste (feces)
Inefficiency of energy transfer
 Energy is also lost to the environment
between levels of food chain as heat
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sun
Ecological Energy Pyramid
 Only 10% of energy is transferred between levels of a food
chain
 can feed fewer animals in each level
Numbers
1
100
100,000
1,000,000,000
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Food webs
 Food chains are

linked together into
food webs
Who eats whom?

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a species may
weave into web at
more than one level