Students will learn how trophic levels differ and are similar among ecosystems.
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 life-the 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:
producers-herbivores-small carnivores-large 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.
Paper, drawing materials
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.
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.
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?
The card game Habistack reinforces the trophic level concepts learned here with a game based on the ecology of Great Sand Dunes.