SBI4U RHSA
Name: ____________________________
Trophic Structure of Ecosystems – V2
All energy for life on Earth comes from the
Sun. The First Law of Thermodynamics states
that “Energy cannot be created or destroyed,
it can only change form.” Only about 1% of
the sunshine that reaches Earth is captured by
plants. This heat and light energy is converted
to chemical energy, in the form of glucose, by
photosynthesis.
The organisms that capture sunshine energy
are called producers or autotrophs, which
means “self food”. Producers are almost
always the first trophic level of any food chain. The word troph derives from the Greek word
for food.
All other organisms are heterotrophs and get energy by consuming other organisms. All
herbivores, omnivores, carnivores and decomposers are heterotrophs. Herbivores , also called
primary consumers, must always be at the second trophic level, as they eat plants. Secondary
consumers could be carnivores or omnivores and are at the third trophic level.
A food chain is one path through a food web. The arrows must always start with the producers
at the first trophic level and go “up” the chain.
Decomposers are often hard to place in a food chain as they consume detritus from multiple
trophic levels. Fungi, worms, and many species of bacteria recycle large organic molecules into
small organic molecules that can be reabsorbed.
The flow of energy is considered to be an open system as there is always more energy arriving
at Earth and some heat energy always leaving Earth. This is the opposite of the nutrient cycles
like nitrogen which are part of a closed system.
Do p 443 #1,3-6, 9
Do Thinking Lab p 449 #1-3 on Bioaccumulation.
Read p 444-450
SBI4U RHSA
Name: ____________________________
Trophic Structure of Ecosystems – V2
All energy for life on Earth comes from the Sun. The
First Law of Thermodynamics states that
“___________________________________________
______.” Only about 1% of the sunshine that reaches
Earth is captured by plants. This heat and light energy
is ____________________ ______________________,
in the form of glucose, by
_______________________.
The organisms that capture sunshine energy are called
_______________ or ______________, which means “self food”. Producers are almost always the
________________________ of any food chain. The word troph derives from the _____ word for food.
All other organisms are heterotrophs and get
______________________________________.
All herbivores, omnivores, carnivores and
decomposers are heterotrophs. Herbivores , also
called _______ _______________, must always be
at the _________ _________ level, as they eat
plants. Secondary consumers could be
_____________ or __________________ and are
at the third trophic level.
On the food web circle an autotroph and draw a square around a secondary trophic level organism.
SBI4U RHSA
Name: ____________________________
A food chain is ___________________________________________________. The arrows must always
start with the producers at the first trophic level and go “up” the chain. Trace one food chain on the
food web diagram on the previous page.
Decomposers are often hard to place in a food chain as they consume ____________ from multiple
trophic levels. Identify decomposer trophic levels as ________________________________________.
Fungi, worms, and many species of bacteria _______________ large organic molecules into small
organic molecules that can be reabsorbed.
Colour code the arrows on this diagram.
The flow of energy is considered to be an _______________ as there is always more energy arriving at
Earth and some heat energy always leaving Earth. This is the opposite of the _____________________
_______________ which are part of a _______________________.
Homework
1. Read p 440-443 and do p 443 #1,3-6,9
2. Do Thinking Lab p 449-450, #1-3 on Biological Magnification.
Review from grade 9
- Bioaccumulation is the build up or increased concentration of a toxic compound in one organism.
- Biological magnification is the increasing concentration of a toxic compound as the trophic level
increases in a food chain.
3. Complete the Trophic Levels Study Chart on the next page.
SBI4U RHSA
Name: ____________________________
Trophic Levels Study Chart – p 440 - 443
The trophic structure of an ecosystem refers to the feeding relationships among its members. Tracing the production and
consumption of food molecules like glucose is a way of tracing energy flow in ecosystems. Tracing one route from a producer
through the consumers and decomposers is one food chain in a food web. Start your answers at trophic level one!!!
Type of
Troph?
Trophic
level #
5
4
3
2
1
Producer or Consumer or Decomposer?
- level and description
Decomposers
- highest trophic level
- recycle large food molecules and break them
into simpler small organic molecules
Aquatic Ecosystem
Example(s)
Terrestrial Ecosystems
Example(s)