Chapter 17 Section 1
Energy Flow in Ecosystems
What are the Components of an
Ecosystem?
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The components of an ecosystem are all the
living and nonliving things that interact in a
particular area.
The organisms in an ecosystem are called biotic
factors.
 Organisms in an ecosystem interact with
one another.
They also interact with the nonliving things, or
abiotic factors.
 Examples of abiotic factors include the sun,
temperature, water, and oxygen.
Habitat
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Organisms need food, water, and living space.
They obtain all these things from their
surroundings.
Every organism lives in a specific environment,
or habitat, that provides the things the organism
needs.
Each species of organism has its own habitat
requirements.
 A species is a group of similar organisms
that can mate with one another and produce
fertile offspring.
The desert cottontail, for example, is a species of
rabbit whose habitat is areas of brush in deserts
and grasslands.
Niche
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Each species of organism has a role, or niche, in
the ecosystem in which it lives.
An organism’s niche includes such things as
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the types of food it eats,
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how it obtains this food, and
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the physical conditions that it needs to
survive and reproduce.
For example, the desert cottontail’s niche
includes the leaves, twigs, grasses, and seed pods
that it eats.
The rabbit’s niche also includes the hawks, owls,
and other organisms that feed on it.
Desert cottontails are usually more active at night
than during the day. This behavior is also part of
the desert cottontail’s niche.
Energy Roles
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An organism’s energy role is
determined by how it obtains
energy and how it interacts
with the other living things in
its ecosystem.
An organism’s energy role in
an ecosystem may be that of a
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producer,
consumer, or
decomposer.
Producers
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Energy first enters most ecosystems
as sunlight.
Some organisms, such as plants,
algae, and certain microorganisms,
are able to capture the energy of
sunlight through photosynthesis and
store it as food energy.
 Organisms that carry out
photosynthesis are called
autotrophs.
Another word for an organism that
can make its own food is a producer.
Producers are the source of all the
food in an ecosystem.
 For example, the grass, oak tree,
and other plants are the producers
for the field ecosystem.
Consumers
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Other members of an ecosystem cannot make their own food.
 These organisms are called heterotrophs.
Heterotrophs depend on the producers for food and energy.
Another word for an organism that obtains energy by feeding
on other organisms is a consumer.
 All animals are consumers.
Consumers are classified by what they eat:
What they eat
Herbivores
Carnivores
Scavengers
Omnivores
only plants
only animals
dead organisms
plants and animals
Examples
caterpillars, cattle, deer
lions, spiders, snakes
catfish and vultures
most humans, goats
Animal
They EAT
Omnivores
plants and
animals
Scavengers
dead
organisms
Carnivores
only animals
Herbivores
only plants
Decomposers
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Organisms that break down wastes
and dead organisms and return the
raw materials to the environment are
called decomposers.
Two major groups of decomposers
are
 bacteria
 fungi
 such as molds and
mushrooms.
While obtaining energy for their own
needs, decomposers return simple
molecules to the environment. These
molecules can then be used again by
other organisms.
Food Chains
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The movement of energy through
an ecosystem can be shown in
diagrams called food chains and
food webs.
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, such as the
grass in the field.
The second organism is a consumer
that eats the producer, and is called
a first-level consumer.
 The mouse is a first-level
consumer.
Next, a second-level consumer eats
the first-level consumer.
 Example: The kestrel.
Food Webs
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A food chain shows one
possible path along which
energy can move through an
ecosystem.
Most producers and
consumers are part of many
food chains.
A more realistic way to
show the flow of energy
through an ecosystem is a
food web.
A food web consists of the
many overlapping food
chains in an ecosystem.
Create a Food
web:
http://www.vta
ide.com/png/fo
odchains.htm
Which organism is the
top consumer in this
food web?
woodpecker
red fox
garter snake
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The pyramid-shaped food chain
shows many trees & shrubs
providing food and energy to
giraffes.
Note that as we go up, there are
fewer giraffes than trees & shrubs
and even fewer lions than giraffes.
In other words, a large mass of
living things at the base is required
to support a few at the top.
Energy Pyramids
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When an organism in an ecosystem eats food, it obtains
energy.
The organism uses some of this energy from food to
move, grow, reproduce, and carry out other life activities.
This means that only some of the energy will be available
to the next organism in the food web.
A diagram called an energy pyramid shows the amount
of energy that moves from one feeding 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.
This is because the organisms at each level use some of
the energy to carry out their life processes.