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Variations
Variation on Web of Life Activity
The following is a learning activity, adapted from Joseph Cornell's book,
Sharing Nature with Children, which vividly illustrates the interdependence
of living things in any ecosystem of your choice. We have chosen the Boreal
Forest of Newfoundland as an example, but you can adapt it as you please
by substituting suitable plants, animals and abiotic factors for the ecosystem
of your choice.
Please note: This activity is usually done with groups of grade 5-7 students.
You may want to adjust your delivery depending on your audience, and give
opportunities for peer teaching throughout the activity.
Materials
- Roll of sturdy string, such as cod line, packing string or twine,
mounted on a spool for easy roll-up.
- Plant/Animal/Abiotic cards, large enough to be seen from 4 meters
away,mounted on color coded Bristol board, preferably with an illustration
where possible, with a piece of string so participants can wear the
card with print facing out so everyone can read it.
In the Newfoundland boreal forest, we have the following:
- Trees: (dark green) Balsam Fir, Red Maple, White Birch, Spruce,
White Pine, and Larch.
- Shrubs: (light green) Willow, Partridgeberry, Bunchberry, Raspberry,
and Wintergreen berry.
- Fungi: (grey) Heart Rot Fungus, and Fungus Partner (for example,
Amanita muscaria).
- Insects: (red) Spruce Budworm, Hemlock Looper, Bark Beetle,
and Ichneumon wasp (larval parasites of H. looper caterpillars etc.).
- Fishes: (blue) Atlantic Salmon, and Brook Trout.
- Birds: (yellow) Woodpecker, Crossbill, Warbler, Grouse, Sparrow,
Grey Jay, and Merganser.
- Land Mammals: (orange) Moose, Red Squirrel, Pine Marten, Field
Mouse, Caribou, Shrew, Snowshoe Hare, Lynx, and Black Bear.
- Abiotic Factors: (white) soil, water, air, and sunlight.
Note: This is obviously an incomplete forest ecosystem. Representative
members that students were already familiar with were chosen from our
school program "The Forest-More Than Just Woods", and some are
deliberately vague hence Sparrow, instead of a specific species. If the
group is less than 36, you can eliminate some of each group of organisms
(for example, use 4 trees instead of 6 species) but retain the soil, water
and air in the abiotic factors group.
Method
- Arrange your students in a circle, with yourself in the middle with
your roll of twine ready.
- Ask who knows the names of some trees that grow in the forests at
your location. As you get responses, appoint students to play the trees,
and give them the appropriate cards to wear around the neck. Have the
lettering facing out so that everyone can read them. It is best to spread
the trees apart i.e., one tree then one shrub, then a fungus, then an
insect, then a bird, then a mammal, then an abiotic, then another tree.
Do the same for the other categories. Continue until all of the students
in the circle have been assigned cards.
- At this point, we look at the relationships between these organisms
and their environment. Pick one of the trees (i.e., Balsam Fir) to start
with. Ask the question, "Who would eat the Balsam Fir?" Give
the student wearing the Balsam Fir card the end of the roll of twine
and wrap it once around their hand.
- When students answer, i.e., Hemlock Looper caterpillars eat Balsam
Fir needles, pass the roll of twine to the student wearing the Hemlock
Looper card and get that student to hold on to the twine by wrapping
it around the hand once.
- Next you might ask, "Who might eat the looper caterpillar?"
and the twine goes to the warbler. You may want to explain that the
looper is connected to the tree because fir is one of the foods of this
caterpillar, and the warbler is connected because it eats all sorts
of insects, but the warbler may also depend on the tree as a secure
nest site.
- Continue connecting the students with the twine as the relationships
are explained, until everyone is connected, holding on to the twine.
At this point we have a representation of the web of life in a forest
ecosystem. Be sure to tell everyone to keep hold of the twine. Remember
that not all the relationships are herbivore-plant, or predator-prey,
you can also illustrate others like symbionts. For example, link one
of the conifers to a fungus partner to demonstrate mycorrhizal symbionts
of conifers.
- To demonstrate the interdependence in this forest ecosystem remove
member. For example, perhaps a fire, windstorm or other natural process
has killed a tree, or perhaps a stressor, like clearcut logging, has
removed entire stands of trees. Remove one tree slowly from the circle,
making sure that he/she keeps hold of the twine. Ask the students who
feel a tug on the twine, to give the twine a tug themselves. Explain
that everyone who has felt a tug has been affected in some way by this
change to the ecosystem.
Caution: Do not yank the tree out suddenly because the pull of
the twine can be painful, wrapped around the hand.
To Unravel the Web: Have everyone to keep hold of the twine and roll
the twine back onto the spool. Collect the cards as you go along.
Conclusion
Explain that real ecosystems are much more complex than the ecosystem
represented in our example. We are just only beginning to discover how
complex. There are many more relationships waiting to be discovered.
Timing: 20-30 minutes for a group of 20-36 students. Larger group
size means a longer time to complete the activity. It is not necessary
to explain all the relationships in detail, just the first, second and
third, and then a few examples of others. The more explanation you do,
the longer it will take.
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