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Energy Flow in an Ecosystem
Energy Flow in an Ecosystem
• Autotrophs: organisms that manufacture
their own nutrients using stored energy or
energy from the sun
– Examples?
• Heterotrophs: cannot make their own
food, they feed on autotrophs or other
heterotrophs
– Examples?
Energy Flow in an Ecosystem
• The sun is the ultimate source of energy for all
organisms
• Producers change light energy into energy they
can use to grow.
– Plants and other photosynthetic organisms
• Consumers eat other organisms instead of
producing their own food
• Decomposers are organisms that break down
the remains of organisms
– Fungi, bacteria, some insects
Types of Consumers
• Herbivores: feed on plants
– Rabbits, grasshoppers, squirrels, etc
• Carnivores: feed on other animals
– Lions, snakes, wolves, etc
• Scavengers: feed on dead animals
– Vultures, crows, etc
• Decomposers: break down and absorb
nutrients from dead organisms
– Fungi, bacteria, some insects
Energy Flow in an Ecosystem
• Energy flows through an ecosystem as
one organism eats another. The way in
which energy flows can determine how
many species can live in an ecosystem.
• Each step in the transfer of energy
through an ecosystem is called a
trophic level
– In an ecosystem, energy flows from the sun
to producers to consumers to decomposers
Trophic Levels in an Ecosystem
Energy Flow in an Ecosystem
• Food Chains
– In an ecosystem, energy
flows from one trophic
level to the next, forming
a food chain
– Simple way to show flow
of energy from one
trophic level to the next
– Arrows point in the
direction of energy flow
Energy Flow in an Ecosystem
• Food Webs
– Energy does not
follow a simple
pattern!
– Many organisms eat
more than one kind
of food
– A group of
interconnected food
chains form a food
web
Energy Flow in an Ecosystem
• Energy is stored at each level of a
food web and moves throughout
trophic levels as organisms feed on
each other. But not all of it is used;
some of it dissipates as heat back
into the environment and does not
move on to the next trophic level….
Energy Flow in an Ecosystem
• Rule of 10
– Also called “The 10% Rule”
– Only TEN (10) PERCENT of the energy
available in a trophic level will move on to
the next!
– The other NINETY (90) percent is changed
into heat energy!
Energy Flow in an Ecosystem
• Energy Pyramid
– Triangular diagram that
shows an ecosystem’s
loss of energy as it
moves through a food
chain
– Each layer represents one
trophic level
• Producers are always at the
base. They have the MOST
energy!
• Consumers make up higher
levels