Symbiotic Strategies
Lesson Activities


1) Clear some room on the classroom whiteboard or on a sheet of posterboard. Review students’ knowledge of different ecological relationships by asking them to generate a list of types of interactions that might exist between different species living close to each other. Write these on the board (for example, Species A might eat Species B, Species A might use Species B’s discarded shell for shelter, etc.) NOTE – the list should focus on interactions between different species, not between members of the same species.

2) Ask the students if they can recall a definition for “symbiosis” (symbiosis is a long-term interaction between different species that interact in close proximity). Write the following on the board in three rows: +,+; +,0; and +,-. These symbols represent the three main types of symbiosis. Ask the students if they remember the term for a symbiotic relationship that benefits both species? (mutualism, +,+). What about one that benefits one species while the other species is not affected? (commensalism, +,0). Finally, what about a symbiotic relationship that benefits one species and harms the other? (parasitism, +,-).

3) As a class, see if you can classify the interactions that the students brainstormed in Step 1 as mutualistic, commensal, parasitic, or none of the above. Once you have identified the symbiotic relationships that the students thought of, point out that additional ecological relationships NOT generally considered to be symbiotic include predation (not a long-term relationship as one species is eaten) and competition (not considered to be a direct interaction between species as the focus is a fight over an external resource).


1) Distribute the “Ecological Relationships Student Organizer” (PDF) (RTF) to each student. Tell your students that they will be watching several video clips that capture ecological relationships between ocean species. They will be making predictions about the relationships between the species and will check their predictions with the information given in the videos.

2) Frame the first clip by telling the students that they will see a tiger shark and a loggerhead turtle interacting in the waters near the Bahamas. Ask your students to silently make a prediction about the relationship between these two animals and to mark it in the appropriate box of the “Ecological Relationships” organizer.

3) Provide your students with a FOCUS FOR MEDIA INTERACTION by asking them to check their prediction as they watch the clip. Play Clip 1, “Shark and Turtle,” for the students (access the video segments for this lesson at the Video Segments Page).

4) Follow up with the students by asking them to name the ecological relationship between the shark and the turtle (predation). Have the students fill in this information on their organizer. Ask the students if anything surprised them about this clip (accept all answers).

5) Frame Clips 2 and 3 for your students by explaining that the next clips will show many pairs of oceangoing species interacting. The list of interacting species pairs can be found on the “Ecological Relationships” organizer. Ask the students to silently predict the relationship they expect to see between each interacting pair of species and to note it on the organizer.

6) Provide your students with a FOCUS FOR MEDIA INTERACTION by asking them to check their predictions as they watch the clip. Play Clip 2 for the students (access the video segments for this lesson at the Video Segments Page). Give the students a few minutes to fill in the “actual relationship” column in the organizer after viewing the clip, noting the name of the relationship and the description of the behavior observed. You may need to play the clip twice for students to record all the information.

7) Play Clip 3 for the students, asking them to fill in the last row on their organizer (access the video segments for this lesson at the Video Segments Page). Follow up the clips by reviewing the relationships using the “Teacher Answer Key” provided (PDF) (RTF). Ask the students to explain if the actual relationships were different than the ones the students predicted.


1) Ask the students to name the types of ecological relationships that were seen between different species in the video clips (predation, competition, mutualism, commensalism). Ask: What type of symbiotic relationship was NOT seen in these clips? (parasitism). Remind the students that parasitism is a symbiotic relationship between two species living together that provides a net gain for one species and a net loss for the other species. It is different from predation in that the relationship is prolonged and ideally does not end in the death of the host – the parasite requires its host to remain alive in order for the parasitic relationship to continue — but it may make the host very sick.

2) Ask the students if they can name any examples of parasitic relationships between species (answers will vary, but some examples include intestinal worms and mammals – for example the tapeworm and the cow; cuckoo birds and other bird species; and fleas and dogs/cats).

3) Explain that one example of a human parasite is the protozoan that causes the disease malaria. These protozoans, of the genus Plasmodium, are especially interesting in that they have TWO species that act as their hosts, not just one. Ask if the students know how malaria is transmitted to humans? (The disease is transmitted by mosquitoes). Point out that it is not the mosquito itself that is the parasite – it is the protozoan that is transmitted from one animal or person to another via the mosquito’s saliva. The mosquito is a vector – an organism that transmits disease but does not cause it.

4) Have the students form groups of 3-4, each with a computer. Tell the groups to visit the Malaria web site from Distribute a “Malaria Student Organizer” (PDF) (RTF) to each group. Give the students approximately 15 minutes to play both the “Mosquito” and the “Parasite” games on the site. Provide the students with a FOCUS FOR MEDIA INTERACTION by asking them to try to successfully complete each of the two challenges and to answer the questions on the Malaria Student Organizer when they are finished.

5) When the groups have finished playing the games, review the “Malaria Student Organizer” as a class (Teacher Answer Key is provided).

6) To reinforce the learning gained in the online game, project the Life Cycle of a Malaria Parasite interactive tour, and walk through each stage to help the students understand the parasitic relationship between the Plasmodium protozoan, the mosquito, and the human.


1) Review the types of ecological relationships studied thus far (predation, competition, mutualism, commensalism, parasitism). Explain that these relationships have evolved over a long period of time between species that coexist. Even the relationships that are detrimental to one species (i.e. predation, parasitism) are integral to the maintenance of ecological balance. But threats to this stability can occur when dramatic events or shifts in behavior throw an ecosystem out of whack. Ask the students to name some examples of events and behaviors that may be dramatic enough to threaten the stability of a particular ecological niche (answers will vary but may include human actions, climate change, pollution, and the like).

2) Frame Clip 4, “Collapse of Sharks,” for the students by explaining that the clip they are about to see will show an ecological relationship that has been thrown out of balance. Provide the students with a FOCUS FOR MEDIA INTERACTION by asking them to explain how the relationship between human and sharks has changed over time. PLAY Clip 4 for the students (access the video segments for this lesson at the Video Segments Page).

3) Review the focus – How has the relationship between humans and sharks changed? (When humans fished for sharks for subsistence and on a small-scale basis, there was no threat to the continued survival of sharks. With the recent dramatic increase in shark fishing that has resulted from the demand for shark fins and shark cartilage, shark populations worldwide are in danger of collapse).

4) Lead a brainstorming session about possible ways that the collapse of shark populations can be averted. As a class, come up with a list of different strategies that might help rectify the situation seen in the clip, restoring ecological balance and preventing the collapse of shark populations.

5) Frame Clip 5, “Sharks in Our Future,” by telling the students that the clip will demonstrate one strategy that is being undertaken to restore the balance in the human-shark relationship. Provide students with a FOCUS FOR MEDIA INTERACTION by asking them to explain how this strategy is helping to solve the problem. Play Clip 5 for the students (access the video segments for this lesson at the Video Segments Page).

6) Review the focus – How is ecotourism helping to restore shark populations? (Ecotourism, an industry that provides opportunities for tourists to pay for the privilege of diving with sharks to observe them in their natural environment, demonstrates that living sharks are just as valuable as dead sharks. Sharks do not need to be killed, and their fins sold, for communities to benefit financially from them. Encouraging this practice helps maintain a healthy population of living sharks.)


1) Form groups or pairs of students. Explain that each group will be investigating a case study of an ecosystem thrown out of balance by human action. Their task is to research the case and formulate an action plan outlining three possible actions that humans could take to restore the ecosystem to balance, and one possible action that the class could make during this school year.

2) Distribute the “Ecosystem Action Plan Student Organizer” (PDF) (RTF)to each group or pair and go over the instructions as a class.

3) Provide the class with a list of case studies they may select. A few examples are below, but feel free to add your own cases to the list (you may also entertain student ideas for case studies):

  • What’s happening to frogs? (What is causing amphibian populations to decline worldwide?)
  • Where have all the wild fish gone? (How is the fishing industry affecting populations of wild fish?)
  • What’s wrong with a fish farm? (What are the effects of factory fish farming on ocean ecosystem health?)
  • Uh oh, I lost my way! (How is increased development harming migratory birds and butterflies?)
  • Romeo, Romeo, I can’t hear you. (What effect are changing undersea sound levels having on ocean species?)

4) Assign a date for class presentations. Provide the students with in-class and homework time to complete their research and plan their presentations.

5) On the assigned date, have each group present its case. Allow for class feedback and discussion. What do the students think of the action plans? Use the “Ecosystem Action Plan Assessment Rubric” (PDF) (RTF) to aid in assessing the presentations.

6) After all the groups have presented, ask the class to make a commitment to follow through during the current school term with at least ONE of the concrete actions outlined by the groups (for example, students might collect signatures on a petition, hold a fundraiser to support a conservation organization, create a video for the school and/or the PTA raising awareness of the issue, or devote one or more days to volunteering for a conservation effort in your region). Once an action has been decided upon, help students uphold their commitment and enact their plan.


English Language Arts
Rachel Carson’s Silent Spring highlights the potential effects of human behaviors on the environment and on ecosystems. In another vein, Henry Thoreau’s Walden provides a riveting account of Thoreau’s experience in the Massachusetts wilderness. Discuss the scenarios presented in this book in light of the relationship between humans and nature. What are the consequences (or potential consequences) of human behavior on the environment if it is not valued or protected? What can be done to protect the planet from these consequences?

Recent studies have suggested that parasitic worms may provide unexpected benefits to the humans they colonize, helping allergy sufferers by calming the allergic response. Have students research this unexpected upside to the worm-human symbiotic relationship.


Invite a local park ranger or invasive species specialist to visit your class to describe threats to fragile ecosystems in your area and measures being undertaken to protect them.

Investigate what ecological restoration efforts are being undertaken in your area. Organize your class to participate in a river cleanup, invasive plant removal day, or native seed planting effort in your region.

Engage your students in a community fundraising effort to provide mosquito nets to people in underdeveloped, malaria-prone areas of the world. The Nothing But Nets campaign is one organization spearheading this effort.

  • Taryn Coffaro

    I am confused as to what the Ecological Relationships student organizer looks like. Am I missing where it can be downloaded?

  • Ivy Mcdaris

    alike to my sort of thought

  • Buter

    It’s provided as a hyperlink near the top of the webpage. “Learning Activity 1: Number1″

  • abe

    shut up tom

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