Transcript Unit 2

Unit 2
Ecosystems and
How They Change

Everything in an ecosystem interacts by 2
main processes:
and

The SUN is the
original energy
source for most
organisms.
SUN
AUTOTROPHS
PRODUCE
PRODUCE
CARBOHYDRATES
(SUGARS)
CARBOHYDRATES
(SUGARS)
AUTOTROPHS
and
AND
HETEROTROPHS
BREAK DOWN
CARBOHYDRATES
TO RELEASE
ENERGY
Photosynthesis
process that converts solar energy into
chemical energy stored in the bonds of organic
compounds, usually carbohydrates
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
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Respiration

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The release of chemical energy from food for
cellular use
C6H12O6 + 6O2  6CO2 + 6H2O + energy
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AUTOTROPHS

Organisms that use energy to
make their own food
(producers)
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HETEROTROPHS
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Organisms that cannot make
their own food (consumers)
Feed on autotrophs or on other
heterotrophs that feed on
autotrophs
All life depends on
AUTOTROPHS.
Name
Who Eats What in an Ecosystem
Energy Source
Examples
Producer
Makes its own food
Consumer
Gets energy by eating
other organisms
Herbivore
Eats only producers
cows, sheep, deer,
grasshoppers
Carnivore
Eats only other
consumers
lions, hawks,
wolves, pike
Omnivore
Eats both producers and
consumers
bears, pigs,
humans
Decomposer
Breaks down dead
organisms, returning
nutrients to the soil or
water
fungi, bacteria
grasses, ferns,
trees, some
bacteria

Specific sequence in
which organisms obtain
energy in an ecosystem
•Usually only 4 or 5
levels
•Only a portion of the
energy available to
organisms at each level of
the food chain is stored
•Only the stored energy is
available to organisms at
the next trophic level

The interrelated food chains in
an ecosystem

Trophic
level
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each step in the transfer
of energy through an
ecosystem
Describes how far an
organism is removed
from plants in a food
chain
An organism cannot
always be assigned to
one trophic level
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Ecosystems seldom have
more than 4 or 5 trophic
levels
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Not enough food or energy to feed another level
Not all the food available at one level is actually
eaten by animals at the next level
Most of the energy is used in respiration, to
repair body tissues, and for locomotion,
circulation, and feeding
5-C MEASURING ENERGY FLOW:
PRODUCTIVITY
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Primary productivity:
rate at which plants make more plant material by
photosynthesis
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Net primary production:
energy available to other organisms
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The world’s food supply
About half is used by plants for respiration
Limits the number of organisms that can survive on earth
the
Numbers Pyramid
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compares the number of individuals
at each trophic level
Biomass Pyramid


compares the amount of biomass
(total dry weight of the organisms in an
ecosystem)
Energy Pyramid


compares the total amount of
energy in each trophic level