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Trophic Levels
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Quick Draw
Background
All ecosystems are based upon the abiotic characteristics of the
landscape and climate. The combined topography, soil type, amount
of precipitation, amount of sunlight, temperature regime, and wind
regime all affect what kind of life will grow in a particular area.
Out of these abiotic factors emerge the first level of lifethe
producers. As a group, producers make up what ecologists refer to
as the first trophic level. Producers are the algae, cyanobacteria,
and plants within an ecosystem. They produce the foods on which
the other trophic levels feed. Trophic levels are simply a way for
ecologists to describe the food chain. It is important to note that
trophic levels are visualized as pyramidal in shape. Because energy
is lost in the form of heat at each level, the quantity of life
that can be supported becomes smaller at each level. All biological
factors decrease at each ascending level: energy, biomass, and number
of organisms.
Biological systems are typically composed of four trophic levels:
producersherbivoressmall carnivoreslarge
carnivores
There are animals that overlap these groupings, such as scavengers
and omnivores.
In this activity, students will create fictitious scenes on paper,
describing interactions within the four trophic levels.
Procedure
In this activity, groups of five or more students will work together
to create artwork that represents concepts of the trophic pyramid.
Gather your students in a circle. It is best to do this while sitting
on the ground with notebooks or sketchbooks. Review the trophic
pyramid. This activity is named Quick Draw because each student
has approximately one minute to draw their contribution. Words may
be written on the paper to describe their drawings. Each student
will start a drawing, then pass it and add a contribution to someone
else's picture.
Give students one to two minutes to complete each phase of their
drawing. Then say "pass" and remind students of the next
thing they are to draw. Students should pass drawings to the person
on their left.
Specify whether students may use real or imaginary plants and animals.
If imaginary, require that appropriate adaptations be included.
Each plant/animal must fit into the ecosystem.
Drawing Phases
- Abiotic (non-living) Characteristics: Draw the abiotic characteristics
of your landscape. Include all the characteristics that will help
the other students know how to draw the organisms in your landscapeland,
topography, water, clouds, sunlight, snow, rocks, dunes, swamp,
etc.
- Primary Producers: Draw the producers that live in the landscape
picture you just received. The producers you add to the drawing
should be designed to survive in this landscape (e.g., palm trees
shouldn't be placed in an arctic environment, unless they have
a special adaptation).
- Herbivores: Draw herbivores that specifically feed on the type
of plants illustrated by the previous student. Be sure that you
draw at least two different types of herbivores.
- Small Carnivores: Draw small carnivores appropriate to your
ecosystem.
- Top Carnivore: Draw the top carnivore of this ecosystem.
After the final session, the 'artwork' should be passed around
the circle until everyone receives their original paper. Have students
look at their pictures and invent a story about what is happening
in the scene, or come up with a description of their ecosystem and
its inhabitants. Some of the illustrated, fictitious ecosystems
will have excellent stories to be told, others will not. Allow students
to tell their compelling stories to the class. Storytelling should
be limited to only a few minutes per student.
An alternative way to initiate this activity is to provide each
student a specific landscape (such as those found at Great
Sand Dunes) and the abiotic characteristics found there. Then
ask them to begin their drawings with the primary producers found
in that ecosystem. More time should be allowed and students should
label the species that they draw. This alternative is only for advanced
students who have already learned about a variety of ecosystems.
Critical Thinking
- As a class, make a list of the wild animals you have seen.
- Why do we see more herbivores than carnivores when we are out
in nature?
- Which trophic level of animals spend the most time eating, and
why?
- Where do humans fall within (or beyond) the trophic pyramid?
- How do we differ from all the other organisms within each trophic
level? How are we similar?
Extensions
The card game Habistack reinforces the
trophic level concepts learned here with a game based on the ecology
of Great Sand Dunes.
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