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TEK: 7.5C: Diagram the flow of energy through living
systems, including food chains, food webs, and energy
pyramids

Organisms fill various energy levels in an
ecosystem
 An organism’s energy level is determined by how it
obtains energy and how it interacts with the other living
things in its ecosystem.

Organisms can be producers, consumers, or
decomposers.
The
energy source for all life on earth starts here!

Organisms that carry
out photosynthesis
(make their own food)
are called autotrophs or
producers.
means "self-feeders".
 Autotrophs come in
many forms, from
trees to algae


The energy that is not used by producers
can be passed on t0 organisms that
cannot make their own energy.

Organisms that cannot make
their own food are called
heterotrophs.
 They depend on the producers for
food and energy.

An organism that obtains energy
by feeding on other organisms is
a consumer.

All animals are consumers.



These are organisms that
cannot make their own
energy (food)
Heterotrophs feed off of
other forms of life.
The term heterotroph can
refer to single or multicelled organisms.
 Herbivores – eat only
Herbivore
plants to obtain energy
 Carnivores – eat only
animals to obtain energy
▪ Predators – hunt and kill
other animals
▪ Scavengers - feed on the
bodies of dead organisms
Carnivore
 Omnivores – eat both
plants and animals to
obtain energy
Omnivore


Are called “primary consumers”
All herbivores
Most of the energy the
primary consumer gets
from the producer is used
by the consumer to carry
out its life processes.
 Some of this energy
moves into the
atmosphere as heat.
 Only 10% of the starting
amount of energy moves
on to the next level


Some energy in the
primary consumer is
not lost to the
atmosphere or used by
the consumer itself.

This energy is available
for another
consumer…


Is called a secondary
consumer
This animal may be
a carnivore,
omnivore, or
scavenger



Most of the energy the secondary consumer
gets from the primary consumer is used by
the secondary consumer to carry out its life
processes.
Some of the energy is lost as heat, but some
energy is stored can be passed on to another
consumer…
Still the 90%, 10% rule applies


Is called a tertiary
consumer
May be a carnivore,
omnivore, or
scavenger


If we start out with
100% from the Sun,
each level uses a
certain amount
(around 90%)
Only 10% of each
level is passed on to
the next energy level

Organisms produce waste and
eventually die. If these wastes
and dead organisms were not
removed from the ecosystem,
they would pile up until they
overwhelmed the living things.

Organisms that break down
wastes and dead organisms and
return the raw materials to the
environment are called
decomposers.
Fungi, protists, bacteria,
and worms are the main
soil decomposers.
Decomposers:
 Aerate the soil
 Break up hard,
compacted soil, and mix
humus through it
 Add organic material
when they die and decay



Humus (pronounced (h)yo͞oməs) - the
organic or once living part of the soil.
It returns the nutrients back to the soil.

So now you
know the
terms, let’s
explore energy
flow (also called
energy transfer)
a bit more.

The transfer of energy from
sun to producer to primary
consumer to secondary
consumer to tertiary consumer
can be shown in a food chain.

Most food chains have no more than four or five links.
 There cannot be too many organisms in a single food chain because
the animals at the end of the chain would not get enough food /
energy to stay alive.
A food chain is a series of events in which one
organism eats another and obtains energy.
 The first organism in a food chain is always a
producer, next is a consumer.
 The chain shows one possible path along which
energy can move through an ecosystem.


The further along the food
chain you go, the less food and
energy is available.

In other words, organisms
along a food chain pass on
much less energy than they
receive.
Remember, this energy is in the
form of sugar (carbohydrates)


A food web consists of
the many overlapping
food chains in an
ecosystem.
 Organisms may play
more than one role in an
ecosystem.
 Coral Reef Food Web
Show the amount of energy
that moves from one feeding
(trophic) level to another in a
food web.
 The most energy is available
at the producer level. At each
level in the pyramid, there is
less available energy than at
the level below.


Since so much energy is lost at each level, the amount of
energy in the producer level limits the number of consumers
the ecosystem can support.
1.
That the amount of available
energy decreases as you go up
the food chain (smallest part
of the pyramid)
2.
It takes a large number of
producers to support a small
number of primary consumers
3.
It takes a large number of
primary consumers to support
a small number of secondary
consumers

Only about 10% of the
energy contained in
one food level is
transferred to the next
higher level.
 The other 90% is
used for the
organism’s life
processes or is lost
as heat to the
environment.



Only 10% of the energy stored by producers
becomes part of the biomass in the bodies of
the first level consumers
The remaining 90% is used within those
bodies. Energy is used to move, eat, live and
keeps the organism warm.
The 90% “loss” (or what is used) only allows
for 10% of the initial energy to be transferred
to the next organism in the chain.
Write the flow of energy with arrows:
Grass
grasshoppers
moles

The pyramid
shows us
visually that
only a few top
consumers can
be supported
owl

Name the three energy roles of organisms in an
ecosystem. How does each type of organism obtain
energy?

Answer:
1. Producers use energy, usually in the form of sunlight, to
make their own food.
2. Consumers obtain energy by eating other living organisms.
3. Decomposers obtain energy by breaking down wastes and
the remains of dead organisms.

Name and define the four types of consumers.
Answer:
1. Herbivores eat only plants.
2. Carnivores eat only animals.
3. Omnivores eat both plants and animals.
4. Scavengers eat the remains of dead
organisms.


Why are food webs a more realistic way of
portraying ecosystems than food chains?
Answer:
Most producers and consumers are part of many
overlapping food chains.


How does the amount of available energy
change from one level of an energy pyramid
to the next level up?
Answer:
Each organism uses 90% of the energy for its
own life processes. Only 10% is available to
the next level consumer.








Energy changes form as it flows through living systems.
The energy role of an organism is that of a producer,
consumer, or decomposer.
Producers are the source of all food in an ecosystem.
Consumers include herbivores, carnivores, and
scavengers, omnivores.
Decomposers return nutrients to the environment
where they can be used again.
A food chain is a series of events in which one organism
eats another and obtains energy. A food web is made
up of the overlapping food chains in an ecosystem.
At each level of an energy pyramid, there is less
available energy than at the level below.