ENERGY IN THE ECOSYSTEM
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Energy from the sun enters and
ecosystem when producers
used the energy to make
organic matter through
photosynthesis.
Glucose is the primary energy
source (carbohydrate) produced
by photosynthesis.
Consumers take in this energy
when they eat producers or
other consumers.
Energy in the Ecosystem
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Plants absorb less than 1% of the sunlight
that reaches them!
However, photosynthetic organisms make
170 billion metric tons of food each
year!
The energy captured by producers is used
to make cells in both producers and
consumers.
TROPHIC LEVELS
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Trophic levels are the
different feeding levels of
organisms in an ecosystem.
Producers are the first trophic
level and consumers make
up several more.
These relationships can be
seen in an ecological
pyramid.
Biomass: the total amount of
organic matter present in a
trophic level. The biomass in
each trophic level is the
amount of energy- in the form
of food- available to the next
THE TEN PERCENT LAW
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Most of the energy that enters through
organisms in a trophic level does not
become biomass. Only energy used to
make biomass remains available to the
next level.
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When all of the energy losses are
added together, only about 10% of the
energy entering one trophic level forms
biomass in the next trophic level. This
is known as the 10 percent law.
MORE TEN PERCENT LAW
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The 10 percent law is the main reason that
most food chains have five or less links.
Because 90 percent of the food chain’s energy
is lost at each level, the amount of available
energy decreases quickly.
10 PERCENT
LAW!!
Heat and Movement
Consumed
Digested
Growth
Not Digested
Waste
Not Consumed
Decomposers
The majority of energy is lost via heat and movement!
ECOLOGICAL PYRAMID
Remember
scavengers and
decomposers can
enter at any level!
Tertiary Consumers= CARNIVORE EATING
OTHER CARNIVORES
Secondary Consumers= CARNIVORES
EATING HERBIVORES
Primary Consumers= HERBIVORES
PRODUCERS = Autotrophic Plants
ECOLOGICAL PYRAMIDS
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Relative amounts of energy are represented in an
ecological pyramid: a diagram that shows the
relative amounts of energy in different trophic
levels in an ecosystem. An ecological pyramid
can show energy, biomass, or the number of
organisms in a food web.
ECOLOGICAL PYRAMID: ENERGY
Shows the relative transfer of energy (joules) from one
trophic level to the next.
ECOLOGICAL PYRAMID: BIOMASS
Shows the relative amounts of organic matter (gram) from
one trophic level to the next.
Ecological Pyramid:
Number of Organisms
Shows the relative number of organisms at each trophic level.
FOOD CHAINS
A Food CHAIN is a series
of organisms that
transfer food between
the trophic levels of an
ecosystem using only
one species at each
level…a simple chain.
 The arrows represent
the flow of energy from
one organism to the
next.
 The arrow points
toward the organism
doing the ‘eating’.
Food Webs
Ecosystems are not as
simple as shown and not
often explained by a
single food chain… Food
WEBS more accurately
show the network of
food chains
representing the
feeding relationships
among organisms in an
ecosystem.
 Most organisms feed on
more than one type of
organism at different
trophic levels.
HOW DO FOOD WEBS SHOW
COMPLEXITY?
 The diversity and stability of an ecosystem is
represented by more complex webs that have
many species and many interactions (lots of
arrows) because they are more stable…more
resistant to disturbance by natural disaster or
human interference. Why?
BIOLOGICAL MAGNIFICATION
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BIOLOGICAL MAGNIFICATION
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The concentration of a pollutant in organisms increases at
higher trophic levels in the food web because these
chemicals build-up in the fatty tissues of these organism
and do not dissolve or flush-out of the organism.
DDT & Mercury examples:
DDT is a pesticide used to kill insects like malaria-carrying
mosquitoes. However, this chemical will magnify in concentration
in larger organisms like birds and mammals and harm their
reproductive abilities.
 Bald eagle populations declined rapidly to the point of extinction
as an endangered species as mother birds were not able to
incubate or hatch their eggs because the eggs shells were too
thin and would crush and break when sat upon to keep warm in
the nest.
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BIOLOGICAL MAGNIFICATION
As the living
organisms eats more,
the concentration of
these substances
increases as they pass
from one trophic level
to the next.
THE DAY IT RAINED
CATS…
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A bizarre case of ecological damage from DDT
occurred in Borneo after the World Health
Organization sprayed huge amounts of the
pesticide. The area's geckos, or lizards, feasted on
the houseflies that had been killed by DDT. The
geckos, in turn, were devoured by local cats.
Unhappily, the cats perished in such large numbers
from DDT poisoning that the rats they once kept in
check began overrunning whole villages. Alarmed
by the threat of plague, WHO officials were forced
to replenish Borneo's supply of cats by parachute.
RELATIONSHIPS IN THE ECOSYSTEM
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Predator/Prey: One organism (predator) will
actively hunt and consume another (prey).
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Competition: two or more organisms of same or
different species compete to use the same
limited resources or basic needs
Symbiotic Relationships
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Parasitism: an organism (parasite)
lives in or on another (host) and
feeds on it without immediately
killing it
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Mutualism: a cooperative
partnership between two
species (both benefit)
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Commensalism: a relationship
where one species benefits and
the other remains unaffected
COEVOLUTION
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When two or more species evolve in response to each other, it is
called coevolution.
 Examples of coevolution may be found between predators and
their prey.
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Plants and insects represent a classic case of coevolution — one that is
often, but not always, mutualistic. Many plants and their pollinators are
so reliant on one another and their relationships are so exclusive that
biologists have good reason to think that the “match” between the two
is the result of a coevolutionary process.