Web of Life Game

designed for the NYC and NYC Watersheds Trout in the Classroom program

Objective:

    To teach students the fragile nature of food webs in a typical trout stream and to learn about keystone species.

Background: 
    Plants and animals found in Catskill Mountains form a delicate food web which relies on the presence and good health of the watershed streams.  These streams carry nutrient rich water feeding hundreds of species of small stream dwelling macroinvertebrates.  The smaller macroinvertebrates feed the larger macrinvertebrates which in turn become a source of food for larger animals such as trout.  Trout and other fish become prey to larger fish, birds and mammals living in the forests.  The cycle continues with the presence of decomposers and plant.  A change in the size of one population in a food chain will affect other populations.   This interdependence of the populations within a food chain helps to maintain the balance in the Catskill Mountain watershed habitats.   

Materials:
Creature Index cards (one per student) - (Sample set: Sun, algae, plankton, leeches, minnows, mollusk, frog, salamander, mayfly, caddisfly larva, dragonfly, garter snake, crayfish, snail, trout, otter, worm, bacteria, damselfly, mink, bird), Ball of string or twine

Procedure:

  1. Review with students how energy moves through a food web. Explain that the activity they will do helps demonstrate the connection among members of an ecosystem. Have students make a large circle.  Distribute one card to each student.
  2. Give the ball of string to the student with the Sun card. Have the Sun choose an organism that is dependent on it for survival (plant). The Sun should retain the end of the string and pass the ball to the plant creating the first string of the web. The plant chooses an organism that is dependent on it for survival (insect) and passes the ball to the insect. 
  3. After students have passed the ball several times, suggest to them that the organism holding the string has just died. Ask: What eats dead matter? (insects, worms) The organism holding the ball passes it on to an insect or earthworm. The game continues until all the students are holding the string by at least one point. There will be a large web of string in the circle.
  4. Discuss with students what they observe about the activity. Ask what would happen if one of the organisms disappeared. To demonstrate, ask the student who has passed the ball of string most often to drop it. Have students directly affected by the loss gently tug the string. As the slack is taken up, ask other students to gently tug as the string as well until all of the students are affected.
  5. After the activity, discuss what affect the loss of even the smallest organism will have on the food web. Ask: What do you think would happen if the acid rain or some other environmental pollution prevented the hatching of the insect larvae?

Wrap Up: 
    Discuss the possible consequences that invasive species such as the Japanese knot weed, Didymo and the Asian Longhorned Beetle can have on an established food web.

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