Download Energy in Ecosystems

Energy in Ecosystems
Energy in Ecosystems Warm Up
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What is the source of energy for the planet?
What are producers vs consumers?
For homework tonight, review divergent vs
convergent evolution
Review genetic drift vs gene flow
Review who can evolve, and where variation
comes from.
Test corrections as warm up tomorrow.
All organisms require energy to live
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Recall Photosynthesis:
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Energy from the sun is “captured”. The energy becomes
chemical energy stored in organic compounds (PE).
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Producers: use energy from the sun to make
their own food (organic compounds)
Usually plants
 Can also be bacteria, plankton, and algae
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Consumers: obtain energy by consuming
organic compounds (eating other living things).
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Can be herbivores or carnivores.
Trophic Level Pyramid
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Trophic level pyramid: a
way to organize organisms
based on the level at
which they feed.
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Producers form the base of
the pyramid. All energy for
an ecosystem originates in
the organic compounds
made by the producers.
Energy flow: the trophic level
pyramid
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Producers form the base of the pyramid.
Primary consumers are the next level, followed by
secondary consumers, then tertiary consumers.
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Energy flows through an ecosystem as
consumers feed on other organisms (i.e.: as they
consume the organic molecules contained
within them).
Energy Flow: Food chains
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All energy in an ecosystem begins with the
producers that make their own food. Energy is
stored within these compounds, so an organism
acquires energy if it consumes these compounds.
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A food chain shows that energy flows
from a producer to a primary
consumer and beyond.
An arrow is drawn
indicating the
movement of food
molecules and,
therefore, energy.
Energy Flow: The Food Web
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Food chains in an ecosystem often overlap as a
result of an organism being eaten by more than
one type of consumer
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Food Web: A diagram that shows how
energy flows between all of the organisms in
an ecosystem (a series of interconnected
food chains)
A Food Web
All organisms require energy
continued…
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Many organisms get their energy from other organisms
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Consumers
 Herbivores– get their energy from eating
plants or other producers (1o consumer)
 Carnivores– get their energy from eating
other animals (2o or 3o consumer)
 Omnivores– eat plants and animals
 Detritivores– eat only “dead” organisms
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Decomposers– bacteria and fungi that break down
large molecules found in waste into smaller molecules
Why is the bottom of the pyramid so
much bigger than the top?
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The size of each level represents the amount of
energy that is available at that level
Only about 10% of the available energy makes it
from one level to the next level (not all of an
organism is eaten, some energy is lost as heat during
metabolism, etc.)
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Since producers create their own food/energy from the sun
or molecules, they have 100% energy
Using the 10% assumption, the primary consumers would
only have 10% of the producers’ original energy
Secondary consumers would have 1%, tertiary consumers
0.10%, etc.
Energy at the
nd
2
trophic level
Amount of
energy
contained
within plant
material eaten
by the
caterpillar
Amount of energy
that is stored in the
body of the
caterpillar that can
potentially be passed
on to the third level.
Pyramid shape continued…
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The result is that
many producers are
required at the bottom
of a pyramid to
support only a few
higher-level
consumers at the very
top
This low level of
energy transfer keeps
food chains fairly
short
Pyramid Shape, cont’d
The pyramid shape of a trophic level diagram also
shows that producers are more numerous than
herbivores, herbivores are more numerous than
secondary consumers, etc.
Why aren’t detritivores part of the
trophic level pyramid?
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Detritivores rarely pass energy onto the next
level in the pyramid. Rather, they obtain some
of the energy that is “lost” in each energy
transfer by consuming the energy in the
“leftovers” that might not otherwise be eaten.
Since they don’t pass energy on to higher levels
of the pyramid, they are not shown in the
pyramid (nor in food chains or food webs)
Why do some ecosystems have more
extensive food webs and species
richness than others?
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Species Richness (Biodiversity) = # of different species in
an area.
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The species richness in an ecosystem is entirely dependent upon the
producers
If conditions (temperature, sunlight, water, etc.) are good
there will be many producers and high primary productivity
(large mass of producers)
More producers = more energy available for consumers =
more consumers=high species richness
Tropical rainforests and estuaries have high productivity and
species richness, while deserts and temperate grasslands have
much lower values
Think of how the
primary productivity of
these areas compare.
More on Species Richness
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Species richness is not only affected by primary
productivity. It is also affected by:
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Area
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“Key stone” Predators
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Habitat destruction and/or fragmentation reduces species richness
If certain predators are removed or low in numbers it reduces species
richness in the lower trophic levels.
Introduction of “foreign” species
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By either competing with endemic species or preying upon them,
some endemic species go extinct and/or their populations are
drastically reduced.
http://www.youtube.com/watch?v=o_RBHfjZsUQ&safe=active
Reintroduction of Gray Wolves led to
increased species richness