topic: Food chains and food webs
activity: Flow of energy through an ecosystem
Students learn about important organisms in ecosystems.
Suggested time: 25 minutes
Summary of key learning points
Students:
- Define organisms involved in the flow of energy in an ecosystem
- Differentiate between photosynthesis and chemosynthesis
- Compare the types of consumers
- Understand the importance of decomposers in an ecosystem
Flow of energy through an ecosystem
5 minutes
Discuss with students the definitions of producer, consumer and decomposer. Students should understand
that all living things require energy which is important for the growth, repair, reproduction and the activities
necessary for survival. This energy comes from the Sun and plants and green algae (collectively called
producers) and are the only organisms that can convert this energy needed for all life on Earth. They do this
by the process called photosynthesis which is essential in providing oxygen and food for all other organisms
in the ecosystem.
Energy in an ecosystem moves in one direction only, from producers through to the consumers. Producers
are at the beginning of a food chain or food web and their energy is passed onto the next organism
(consumer) when it is eaten. Only 5-20% of the energy is passed on from one organism to the next because
each organism uses the energy for such things as movement, body heat, wastes and growth.
Energy is not the only thing that being transferred from one organism to the next. Matter (the atoms of
organisms) is also being transferred. Energy however, is not recycled, whereas decomposers recycle the
matter by breaking down dead and decaying organisms to release nutrients into the soil for plants to use in
their growth.
More about producers
5 minutes
Students learn that producers are autotrophs and create their own food. Most autotrophs use photosynthesis
to do this, but some extremophiles use chemosynthesis.
Answer:
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topic: Food chains and food webs
activity: Flow of energy through an ecosystem
Photosynthesis uses light while chemosynthesis doesn't. (Inquiry point 1)
More about consumers
10 minutes
Students learn that consumers are heterotrophs and must consume other organisms to survive. There are
different levels of consumers.
Answers: (Inquiry point 2 if all correct)
Herbivore = rabbit
Carnivore = eagle
Primary consumer = rabbit
Secondary consumer = snake
Tertiary consumer = eagle
More about decomposers
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topic: Food chains and food webs
activity: Flow of energy through an ecosystem
5 minutes
Decomposers are vital to ecosystems because they allow nutrients to be recycled.
Suggested answer: (Inquiry point 3)
Bacteria produce chemicals, called enzymes, that digest dead material. The digested material then provides
a food source for other organisms in the soil. This makes the role of a decomposer extremely important in an
ecosystem. Without them, organic matter would pile up on the ground and plants would not receive the
required nutrients necessary for their survival. The decomposing process greatly increases the nutrient-load
of an ecosystem.
Suggested completion levels
Basic - Inquiry point goal = 2
Students at this level will: define the terms 'producer', 'consumer' and 'decomposer'; state that most
producers use photosynthesis; identify the role of producers.
Core - Inquiry point goal = 3
Students at this level will: explain what a producer is and its role in ecosystems; describe the role of
consumers; identify the different levels of consumers; assess the importance of decomposers in
ecosystems.
Advanced - Inquiry point goal = 3
Students at this level will: explain how producers drive ecosystems; identify the difference between
photosynthesis and chemosynthesis; describe the different types of consumers found in ecosystems using
examples; evaluate the importance of decomposers to ecosystems using examples.
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