Producers, Consumers, & Decomposers
In an ecosystem living organisms or biotic
factors are also grouped by how they get food for
energy. There are three main groups that each
have different roles. Each group depends on each
other and could not survive if one group were
removed.
producers (Autotrophs) – self eating
consumers (heterotrophs) - eating others
decomposers
flow of energy - producers to consumers to decomposers
Producers, also called autotrophs, are
organisms that make their own food by a chemical
process called photosynthesis. Most producers
are green plants. However a few monerans
(bacteria), protists (large single
celled organisms), and fungi are also
producers.
Producers have special organelles (miniature
organs) in each cell called chloroplasts that
contain molecules called pigments.
These pigments absorb energy
from the sun.
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Chlorophyll is the main pigment that gives
plants their green color. Photosynthesis is the
chemical process by which producers capture light
energy from the sun and use it to combine water
with air to form sugar or food. The chemical
equation is:
6CO2 + 6H2O + light energy
C6H12O6 + 6O2
carbon dioxide + water + sunlight yields sugar (food) and oxygen
Why do leaves change
colors in the Fall?
chlorophyll leaves because of less sunlight
exposing orange, red, and yellow
xanthophyll and carotene pigments
The food that producers
make supplies them with
energy and also becomes a
source of energy for the
organisms that eat the
producers. Without plants
(the primary producers) consumers and
decomposers would not be able to live. Producers
always start every food chain.
Food Chain: producer
consumer
consumer
decomposer
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A consumer, also called a heterotroph, is an
organism that cannot make its own food. It
must eat producers or other organisms for
energy. All animals are consumers. A few
protists and a very few exotic plants are also
consumers.
respiration = metabolism = eating
Consumers make food through a process called
respiration. Oxygen and sugar are combined to produce
carbon dioxide, water and energy. Consumers breathe
in the oxygen that is produced by the
photosynthesizers. The oxygen is used to break down
the food to release energy that powers all life
processes. The breakdown of food also produces
carbon dioxide which is removed from the body when
we exhale. The chemical equation is:
C6H12O6 + 6O2
sugar
(glucose)
oxygen
6CO2 + 6H2O + energy
carbon
dioxide
water
respiration: big scale is breathing,
small scale is cell eating
photosynthesis: stores energy for producers
respiration: release energy for movement
for consumers
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There are many kinds of consumers:
(I) herbivore (primary consumer) - eats only plants;
includes cows, zebras, horses, deer, some insects
(II) carnivores (secondary consumer) - eats only other
consumers (meat); includes cats, owls, seals,
spiders, seals, hawks
(III) omnivore (tertiary consumer) - eats both plants
and animals; includes raccoons, monkeys, bears,
skunks, turtles
(IV) scavengers - animals that feed on the bodies of
dead animals; includes vultures, hyenas, worms
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Decomposers are organisms that get energy by
decaying or breaking down chemically the remains of
dead organisms. They are nature’s recyclers. Most
bacteria and fungi and some protists are decomposers.
When an organism dies, decomposers decay the body
extracting the last bit of energy from it. The common
left over materials such as water, carbon dioxide, and
minerals can then be reused by producers to make
sugar through photosynthesis.
Decomposers get energy through respiration, so
they are heterotrophs. However, their energy is
obtained at the cellular level, so they are called
decomposers not consumers.
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The nitrogen cycle is the movement of nitrogen
from the environment into living organisms and back
into the environment. Nitrogen makes up about 78% of
the earth’s atmosphere. It is necessary for all living
organisms because it is the primary building block in
proteins and DNA.
N2 = air
NO3 = nitrates = usable by animals, turned into proteins and DNA
NO2 = nitrites (poisonous for animals)
NH4 (ammonia)
The nitrogen in the air cannot be used by
producers and consumers. It must be fixed or
converted by bacteria in the ground into a useable form
for plants called nitrates. Some plants called legumes
(beans and clover) actually have bacteria in their roots.
Once the plants use the nitrates, consumers eat the
plants so the nitrogen is transferred. The consumers
die and give off wastes transferring the nitrates back
to the environment. Other bacteria unfix the nitrates,
or change it back into nitrogen returning
it into the air. The cycle then starts
over again.
Fixers= decomposers that change nitrogen
into a useful form for plants and animals
(legumes – nodules on bean roots,
symbiosis - mutualism)
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nitrogen cycle
air/lightning fixing
bacteria - fixing
plants
animals
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carbon cycle
The carbon released by consumers and
decomposers is essential to all living organisms
because it is part of all biological molecules. The
carbon cycle is the movement of carbon from the
environment into living things and back into the
environment. Carbon dioxide is removed from the
air and used by producers during photosynthesis.
Most consumers get the carbon they need from
eating the producers. Carbon is released back into
the environment in three ways:
during the respiration (breathing) of consumers
during decomposition
during combustion - the burning of coal, oil, natural
gas, and other fossil fuels
combustion,
decomposition
plants
carbon dioxide
oxygen
animals
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In general, the flow of energy in an ecosystem
starts with sunlight (the ultimate source of all
energy on Earth) which is absorbed by the
producers, goes to the consumers, then to the
decomposers, and back to the producers to start
all over again.
SUNLIGHT ENERGY
Plants make food through
photosynthesis.
The nutrients made by the
decomposer are used by
the producers.
After the consumer
dies, it is recycled by
the decomposers.
The plants are eaten
by consumers.
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Food chains show how the flow of energy in an
environment moves from one organism to the next.
Food chains always start with producers! Sunlight is
not alive so sometimes it is not shown. Organisms get
eaten by the organism
the arrow is pointing to.
For example an animal
goes into the mouth of
another animal.
Food webs are interconnected food chains. They
show how food chains are related and are usually very
complex because most consumers eat a variety of
different foods and can be eaten by a variety of other
consumers. Food chains and webs always start with
producers!!!!
Technically speaking,
scavengers and
decomposers are not part of
the energy food chain/web or
pyramid because they do not
kill and eat thereby
transferring energy from one
organism to another.
Sometimes they are shown
at the top of the pyramid or
at the end of the web.
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As energy flows in an ecosystem from
producers to consumers to decomposers, about
90% of the total energy is lost at each feeding
level in the chain because most of the energy is
either used by the organism or is given off as
heat. The loss of energy at each level can be
represented by an energy pyramid. Because of
the energy loss, the amount of energy levels in an
ecosystem is limited to about 3-5.
10% rule: An average of only 10% of the
energy in one trophic level is passed to the
next trophic level.
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The energy pyramid has a large base and
becomes smaller at the top. At the base or the
first level are the producers. The energy and the
number of organisms are very high. At the second
level are the various consumers. For each level or
feeding stage the energy and number of organisms
decreases so the pyramid becomes smaller at the
top.
Organisms on top eat the ones below; producers are on
the bottom because they get their energy from the sun!
Producers - first level
Herbivores -second level, primary consumers
Carnivores - third level, secondary consumers
Omnivores - top, tertiary
consumers, because they eat everything.
The bottom of the triangle has to be larger than the top
because the things on top eat the things below. If the
pyramid was flipped (smaller on the bottom),
there would be fewer organism and not
enough food. So, the whole ecosystem
would collapse. Sometimes limiting
factors cause pyramids to be inverted
destroying ecosystems.