Colorado Agriscience Curriculum
Section:
Plant & Soil Science
Unit:
Plant Science
Lesson Number:
10
Lesson Title:
What Makes Ecosystems Work
Colorado Agricultural Education Standards:
Standard ESC11/12.10 The student will demonstrate understanding of the principles of
natural resource management in the context of systematics.
Competency ESC11/12.10.01 Understand how systems interact and principles of
natural and artificial fluctuations in ecological systems.
Colorado Science Standards:
Standard 3.1 Students know and understand the characteristics of living things, the
diversity of life, and how living things interact with each other and with their
environment.
Benchmark 3.1.4 Explain how changes in an ecosystem affect biodiversity and
how biodiversity contributes to an ecosystem’s stability.
Benchmark 3.1.5 Analyze the dynamic equilibrium of ecosystems, including
interactions among living and non-living components.
Student Learning Objectives
As a result of this lesson, the student will …
Objective #1 Know how to identify an ecosystem using the terms biotic and abiotic.
Objective #2 Understand food chains.
Objective #3 Know what the biotic pyramid is.
Objective #4 Understand ecological succession.
Time: Instruction time for this lesson: 50 minutes.
Unit 1, Lesson 10: What Makes Ecosystems Work
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Resources:
Natural Resources Conservation Service - The Soil Food Web by Elaine Ingham
http://soils.usda.gov/sqi/soil_quality/soil_biology/soil_food_web.html
Penn State New Kensington - Virtual Nature Trail showing ecological succession
http://www.nk.psu.edu/naturetrail/walk/obs1.htm
University of Nebraska at Omaha - The Biotic Pyramid
http://www.unomaha.edu/~greer/2500/mats/landeth/index3.htm
Tools, Equipment, and Supplies
Review content and be prepared to discuss with students ecosystems in your area with
which they can easily identify.
Consider planning a field trip in which students can observe ecological factors.
Key Terms
Abiotic
Biotic
Biotic Pyramid
Climax Community
Ecological Succession
Primary Succession
Secondary Succession
Ecosystem
Food Chain
Habitat
Photosynthesis
Solar Energy
Interest Approach
Have student enter, read, and play some of the easy to use learning activities found on the
following web site.
http://www.vtaide.com/png/foodchains.htm
From the activities you found and participated in on the web site given to you today you
know we will be discussing to some degree about food chains.
Food chains are just part of an ecosystem which is the big picture of what we are going to
discuss today.
Summary of Content and Teaching Strategies
Objective 1. Know how to identify an ecosystem using the terms biotic and abiotic.
“A Biotic community and its abiotic environment” are two terms you will need to
understand to define an ecosystem.
Unit 1, Lesson 10: What Makes Ecosystems Work
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Proceed through PowerPoint slides.
A biotic community is made up of all the living organisms in the ecosystem and their
interaction. These include plants, animals and microorganisms.
Proceed through PowerPoint slides.
The abiotic environment is made up of nonliving parts of the ecosystem. These include
space, soil, water, sunlight and climate.
Living organisms use energy and matter to live.
To get energy and matter, they interact with both their abiotic environment and with other
biotic organisms.
This interaction is sometimes referred to as the web of life.
Proceed through PowerPoint slides.

Energy used to support life follows a one-way cycle through the environment in what
scientists call food chains.

The three main types of matter used by biotic organisms are carbon, nitrogen and water.

Again, these three recycle through the environment in what are called the carbon cycle,
the nitrogen cycle and the hydrologic cycle.
Nonliving, abiotic factors set the limits on how the biotic communities will grow. The
amount of sunlight, for example, determines the types of plants that will grow in any
given location. So does the type of soil, the amount of water available and the climate.
Some plants can survive early frost and thus are more likely to grow in northern areas.
Plants that are killed by freezing temperatures are limited to southern areas where
temperatures remain warmer the year around.
The type of animals that live in an area will depend upon the kinds of plants available for
food.
In addition, types of animals, birds and fish depend upon climate, temperature and
the cover available for animals.
The term habitat is often used for the combination of factors needed for an animal.
Unit 1, Lesson 10: What Makes Ecosystems Work
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Objective 2. Understand food chains.
Another important factor contributing to the ecosystem is the food chain.
Food chains provide the energy plants, animals and humans need to live.
Proceed through PowerPoint slides.
The chain includes two types of workers -- producers and decomposers -- who provide
energy to those who use energy, also known as the consumers. For review, the two
worker types are….?
Proceed through PowerPoint slides.

Producers are green plants that use photosynthesis to draw solar energy from the sun to
grow and produce food for other organisms.
Proceed through PowerPoint slides.

Decomposers break down waste products and dead organisms into chemical substances,
such as nitrates and carbon dioxide. These are recycled into soil, air and water where they
can be used by plants and other organisms.
Proceed through PowerPoint slides.
Consumer organisms must depend on these two types of "workers," because they are
unable to manufacture their own food. Consumers include animals, humans, birds and
fish. The food chain operates through three phases:
Proceed through PowerPoint slides.
First, green plants use energy from the sun to grow, using nitrogen from nitrates in the
soil and carbon from carbon dioxide in the air to produce protein and carbohydrates.
Next, plants are eaten as food by consumer animals, fish or other organisms. These plant
eaters may, in turn, be eaten by meat-eating animals, fish or humans. In addition, some
plant eaters produce eggs or milk that can be used by humans, or be stolen in the wild by
predator animals.
When plants and animals die, they become waste material in the environment. This waste
is then recycled into the environment by decomposers - mainly microorganisms that
release carbon dioxide, nitrites and nitrates.
Unit 1, Lesson 10: What Makes Ecosystems Work
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Objective 3. Know what the biotic pyramid is.
A combination of all the possible food chains in an ecosystem is called the food web.
This web can be viewed in the shape of a pyramid, with decomposers and producers
forming the lower part of the pyramid and various types of consumers making up the top
layers and the peak.
The whole system takes the shape of a pyramid because energy is lost in the form of heat
each time something is consumed. Therefore, every ecosystem must have more producers
than consumers.

Thus the base of the pyramid is made up of the decomposer organisms found mainly in
the soil.

At the level just above the decomposers are the plants that grow on soil and get their
energy from the sun.

As the pyramid narrows, the next group includes the consumers of plants, followed by
humans and animals that consume both plants and animal products.

The peak of the pyramid would include animals that depend entirely on eating meat from
birds, fish and other animals.
Objective 4. Understand ecological succession.
Ecosystems change over time. Changes can take place because the environment is
changed and/or new living organisms are introduced. Ecosystems also change through a
predictable natural succession. This ecological succession is gradual and usually occurs
over a long period of time.
Ecological succession does not continue forever. Each stage leads to a final climax stage
resulting in a stable community. This climax community is not replaced unless there is a
change on conditions. Two examples:

Prairie grasses growing in some areas may be gradually replaced by shrubs and then by
trees. The prairie grass needs sunlight, so it is unable to compete with the shrubs, while
the shrubs are unable to compete with the trees. Over time the area will become a "climax
community" forest.

A pond will gradually fill in with silt and organic waste. Plants begin to grow at the edges
trapping more silt and organic matter, gradually filling in the entire pond. As the basin is
filled, the types of plants change, with shrubs and trees eventually replacing grass and
smaller plants.
Unit 1, Lesson 10: What Makes Ecosystems Work
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The above examples are called primary successions, as they take place as a natural
transformation of one community to the next. New successions can also be triggered
when land is disturbed. These are called secondary successions. They may start as the
result of plowing or clear-cutting as well as by fire or flooding.
Review/Summary.
In this lesson we have better defined what an ecosystem is and explained how everything
works together in a chain reaction to facilitate the workings of an ecosystem.
I hope the next time you are out enjoying the outdoors you will have a better
understanding of the things that are happening and know that it is part of a chain of events
and not just a single event taking place.
Application
Extended classroom activity:
Identify an ecosystem in your area and discuss in class, and/or write a report for your
teacher to answer the following:
1. How would you describe the ecosystem? What does it look like? What plants and
animals can you find there?
2. Explain how the ecosystem you have selected works. What makes it possible for
various life forms to live there?
3. Draw a biotic pyramid for the ecosystem you have selected. List the biotic life forms
you identified at their proper locations on the pyramid.
Extended classroom activity Answers
1. Answers will vary depending upon type of ecosystem selected. Students should be able
to identify specific plants and animals as producers and consumers within the ecosystem,
as will as recognizing that decomposers are present and at work.
2. Students should explain the functions of the ecosystem in terms of the food chains as
well as abiotic factors such as soil types, typography, amount of water and sunlight.
Examples: In a forest sunlight may be limited by trees; in a pond it may be limited by
excess plant growth. Amounts of water and drainage can make a big difference. A
wetland where water is trapped will support different types of plants and animal life than
will a well-drained area or a desert.
Unit 1, Lesson 10: What Makes Ecosystems Work
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3. Pyramids should have decomposers at its base, followed by producer plants. Plantconsuming life forms should make up the mid to upper part of the pyramid, while meateating carnivores are at the peak.
FFA activity:
Invite a member of the local wildlife department to discuss the ecosystem in your area at
the next chapter meeting.
SAE activity:
Design a project to improve the ecosystem in your area.
Evaluation.
Student evaluation attached to this lesson.
Answers to Assessment:
1. D. Living organisms interacting in an ecosystem
2. FALSE. Abiotic refers to nonliving factors such as water, soil, air, climate and space.
3. A. A food chain
4. C. Life forms that cannot produce their own food
5. FALSE. The process is called an ecological succession.
Unit 1, Lesson 10: What Makes Ecosystems Work
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Student Evaluation
1. The term "community" as used in this lesson is best defined as:
A. The physical environment of an ecosystem
B. The animals and plants in an ecosystem
C. The abiotic organisms in an ecosystem
D. Living organisms interacting in an ecosystem
2. Abiotic factors that influence an ecosystem include all the living organisms found in that
ecosystem.
TRUE or FALSE?
3. A sequence of organisms through which food energy passes in an ecosystem is called:
A. A food chain
B. A succession of carbon
C. Photosynthesis
D. The nitrogen cycle
4. The term "consumers" as used in this lesson is best defined as:
A. The end-point of food chain
B. The beginning of a food chain
C. Life forms that cannot produce their own food
D. Those who endanger the environment
5. The gradual process in which range or grass land first becomes overgrown with brush and later
trees turning it into a forest is defined as an ecological transformation.
TRUE or FALSE?
Unit 1, Lesson 10: What Makes Ecosystems Work
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