Download Following Energy Movement in Ecosystems

11/28/2013
Following Energy Movement in
Ecosystems
Understanding Energy Flows
In order to understand energy flows, we categorize living
things by their “Trophic Level”.
What is a Trophic Level?
– A Trophic Level is a measure of how
living things get their energy.
Classification of Organisms
There are TWO main classes of organisms:
1) AUTOTROPHS
2) HETEROTROPHS
Autotrophs
– Organisms that make their own food from
basic nutrients and light from the sun.
-These organisms are also called PRODUCERS.
-They belong in the FIRST trophic level
(they form the base of any food web).
Example: Plants and algae
Heterotrophs
What is a Heterotroph?
– Organisms that cannot make their own food.
-They must obtain their food and energy from
autotrophs or other heterotrophs.
Heterotrophs are also known as CONSUMERS
-Consumers can belong to the second, third, or
any higher trophic level.
Autotrophs
We know that autotrophs make their own food – but there are TWO
ways that they can make food.
In order to tell the difference – we put them in different categories:
Photosynthetic Organisms
Chemosynthetic Organisms
– Use the energy from the sun
to make their own food.
– Use energy from chemical
reactions to make food
Example: Grass and other plants
Example: Certain types of bacteria
Heterotrophs
There are 5 types of heterotrophs:
-Omnivores
-Carnivores
-Herbivores
-Scavengers
-Decomposers
1) Omnivores – Eat plants AND animals
Example: The Black Bear eats a variety of foods including
fruit, nuts, small deer and fish.
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Heterotrophs
Heterotrophs
2) Carnivores– Eat animals only
5) Decomposers – Breaks down dead organisms
-This completes the circle of life by
returning nutrients into the soil.
Example: Lions – A male lion can eat up to 75 pounds
of meat during one meal!
Example: Bacteria, maggots, worms, etc
3) Herbivores– Eat plants only
Example: Cows – they can eat different plants such as
grass, grains, and hay.
4) Scavengers– Eat dead animals
Example: Vultures – they aren’t very picky about what they
eat, as long as it is dead and rotting.
Food Chains
Food Chains
Food chain– A way of showing a step-by-step sequence of
who eats whom in an ecosystem.
What does this food chain tell us?
The plant is eaten by the slug.
The slug is eaten by the frog.
The frog is eaten by the heron.
What is happening in this food chain?
Insect  Frog
•The slug receives its energy 2 steps
away from the original source
(sunlight).
•Therefore it is in the 2nd trophic level.
The direction of the arrow indicates the FLOW OF ENERGY
and can be read as “eaten by”
(example – Insect is eaten by the frog)
Slug
*If the slug is in the 2nd trophic level
which level is the frog in?
Food Chains
Ok – so, since the frog is in the 3rd
trophic level then the Heron who eats
the frog is a member of the 4th
trophic level?
Plants
Frog
Food Webs
Heron
-The heron is the FINAL carnivore in
this food chain.
*The final carnivore in any food chain
is called the TOP CARNIVORE
Heron
Plants
Frog
Slug
Food Web – a picture representation of the feeding
relationships among organisms in an ecosystem.
- In this food web, you can see that
the fox and the owl have many
different food sources.
- The loss of any one member in this
web will have a serious effect on all
of the other organisms.
It is important to remember that: decomposers can be found at any
level in the food chain, even if they are not shown!
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Trophic Levels
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