K-12 Teaching and Learning From the UNC School of Education

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This lesson is designed to reinforce students’ understanding of the three types of symbiotic relationships (mutualism, commensalism, and parasitism) as well as predator/prey relationships. Using the list of requirements on the worksheet below, students creatively suggest a way in which two imaginary creatures could form a symbiotic relationship.

Teacher preparation

Materials needed

  • Mix-and-match ecology worksheet — one copy for each student
  • One overhead copy of the worksheet for use during recap
  • Overhead projector
  • Colored pencils or markers
  • Blank paper

Classroom Time Required

30-45 minutes


Students should be familiar with some examples of the three types of symbiosis. Common examples include:

  • Mutualism: Cleaner shrimp on sharks (both benefit)
  • Commensalism: Barnacles on whales (barnacles benefit, whales are unaffected)
  • Parasitism: Ticks on dogs (ticks benefit, dogs are harmed)


  1. Hand out the worksheet. Divide students into small groups of 2-3 and have them spend 10-15 minutes brainstorming several symbiotic relationships among the imaginary creatures on the worksheet.
  2. Have students choose two imaginary creatures and at least one of the listed needs. Students should invent the details describing which creature has the need and how it is met by the symbiotic relationship.
  3. Instruct students to designate which of the three types of symbiosis each relationship represents. Remind students that in mutualistic relationships both organisms have a need that is met, while in parasitsm and commensalism only one of the creatures will have a need to be met. Tell students that in order to create each relationship, students must get creative and make up details about the niche of each imaginary creature. For example, students might choose to make a symbiotic relationship between a Majooka and Coblatty by saying that the Majooka needs a warm moist place to live and the Coblatty needs its eyes to be cleaned. Therefore, the students pretend that the Majooka lives inside of the Coblatty’s eyes and cleans them. Clarify that the fabricated information does not have to carry over from one symbiotic relationship to another. For example, the relationship mentioned above portrays the Majooka as a very small organism. In another example students may decide to make the Majooka large and parasitic.
  4. Call time and choose one of the closing activities:
    Closing activity option #1 (requires less time)
    Instruct groups to choose their best symbiotic relationship to present to the class. Use the overhead to help focus student attention during presentations. Have a representative from each group circle his or her group’s combinations on the overhead as they describe the relationship to the class.
    Closing activity option #2 (requires more time but may be more interesting for students)
    Have groups illustrate three of their relationships (one for each type of symbiosis). Students can get creative depicting the creatures since they have only names and their own fabricated information to rely on. Have each group display its drawings (either just one or all three) while the rest of the class guesses which creatures are involved and what type of symbiosis is represented.

Extension and follow-up

  • Discuss the following questions with your students, and then direct them to Wikipedia’s article about symbiosis to discover the answers.
    • What would you guess is the meaning of ectosymbiosis vs. endosymbiosis?
    • The term co-evolution refers to the idea that two species exert pressures on the other over many generations and thus drive change over time in each others’ population. Describe how symbiosis can drive the joint change over time that two species undergo. Can you think of any specific examples?
  • Have students access Wikipedia’s article about symbiosis, which contains links to many interesting organisms that participate in symbiotic relationships. Have each student choose one of the three types of symbiosis and follow the links to learn more about the organisms involved. You may choose to have the students present their findings to the class.


  • North Carolina Essential Standards
    • Science (2010)
      • Biology

        • Bio.2.1 Analyze the interdependence of living organisms within their environments. Bio.2.1.1 Analyze the flow of energy and cycling of matter (water, carbon, nitrogen and oxygen) through ecosystems relating the significance of each to maintaining the health...
      • Grade 8

        • 8.L.3 Understand how organisms interact with and respond to the biotic and abiotic components of their environment. 8.L.3.1 Explain how factors such as food, water, shelter and space affect populations in an ecosystem. 8.L.3.2 Summarize the relationships among...

North Carolina curriculum alignment

Science (2005)

Grade 9–12 — Biology

  • Goal 5: The learner will develop an understanding of the ecological relationships among organisms.
    • Objective 5.01: Investigate and analyze the interrelationships among organisms, populations, communities, and ecosystems.
      • Techniques of field ecology.
      • Abiotic and biotic factors.
      • Carrying capacity.