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McREL Standards Activity


Broken Chains and Tangled Webs


Purpose:As a result of this activity, students will understand how organisms are connected through food chains and food webs in ecosystems and the implications of removing one of the organisms.
Related Standard & Benchmarks:
Science
 Standard 6.Understands relationships among organisms and their physical environment
   Level III [Grade 6-8]
   Benchmark 3. Knows ways in which organisms interact and depend on one another through food chains and food webs in an ecosystem (e.g., producer/consumer, predator/prey, parasite/host, relationships that are mutually beneficial or competitive)
Student Product:

  • Resources for researching various ecosystems (e.g., nature magazines, text books, encyclopedias, the Internet)
  • Various materials for presentations (will vary depending on the type of presentations students choose to develop)
Material & Resources:

  • This activity assumes that students have already studied food chains and food webs in various ecosystems.
  • Be prepared to provide ideas and examples of visual food chains and food webs for the selected ecosystems.
Teacher's Note:Students should choose an ecosystem they find interesting (e.g., an ocean, a prairie, a jungle, a desert, the high tundra, a deciduous forest); some may be more comfortable choosing an ecosystem with which they are familiar.  Students should use the available resources to research their selected ecosystem and its organisms as necessary to supplement their existing knowledge.  They should then use this information to create a visual food chain or food web showing the interrelationships of organisms in the selected ecosystem; they should choose one major producer, consumer, or decomposer in the ecosystem to focus on and organize their food chain or food web so that it shows how this organism is connected (directly or indirectly) to other organisms in the food chain or food web.  Then students should imagine that the selected organism has suddenly disappeared from the ecosystem and consider the following:

  • How might the other organisms be affected by the removal of this organism from the ecosystem?
  • Do you think the food chain or food web can continue without this organism?
  • What do you predict will eventually happen to the ecosystem as a result of the removal of this organism?
  • Based on your answers to the above questions, how would you describe the relationships that exist among organisms in food chains and food webs?

Students should create a visual, written, oral, or multimedia presentation that addresses these questions and present it to the class.

Activity