Ecosystems are complicated places where all manner of different plants and animals interact with each other in often unexpected ways. Quite often, when one aspect of an ecosystem is "manipulated," another seemingly unrelated part is adversely affected. Sometimes, if the wrong part of an ecosystem is destroyed (plant or animal), the entire ecosystem can fall apart, or "crash". This pivotal species is often referred to by scientists as a keystone species. This exercise can dramatically illustrate the delicate balance between organisms in Lake Pontchartrain's numerous ecosystems and even the balance between the various ecosystems.
Can You Name Some of The Ecosystems Located Around Lake Pontchartrain?
|Upland Forests||Pine, Beech, Oak, Hickory||Wild Turkey, Deer|
|Bottomland Hardwood Forests||Magnolia, Ash, Oak, Sweetgum||Weasels, Skunks, Opossums, Racoons, Deer|
|Cypres/Tupelo Swamp||Baldcypress, Tupelo Gum, Ash ||Alligator, Nutria, Heron, Boar, Deer|
|Fresh Marsh||Bulltongue, Palmetto, Cattail||Alligator, Nutria, Ducks|
|Intermediate Marsh||Bulltongue, Cordgrass, Spikerush, Bullrush||Nutria, Blue crabs, Egrets, Ducks|
|Salt Marsh||Saltwort, Smooth Cordgrass, Black Needlerush||Hermit Crabs, Speckled trout, Redfish, Muskrat, Pelicans|
- Lots of wooden blocks of uniform sizes (these can be obtained from construction sites at no cost and cut to uniform sizes)
- Colored pencils to draw organisms on the blocks...or...
- Lots of small photos cut from magazines which depict the various aspects of an ecosystem...plants, insects, fish, bacteria, eagles, etc...use your imagination!
- Scissors to cut the pictures to size
- Glue to fasten the pictures to the sides of the blocks
- It is helpful if the blocks have been sanded to minimize splinters.
- Pictures should be cut out and trimmed to fit on the sides of the blocks (this can be an entire excercise...i.e., "find and cut-out pictures of organisms in a...[insert what type of ecosystem here]...ecosystem"); this prompts a discussion of food webs and eco-pyramids...
- A sturdy low table is necessary, as is some clear space around it (for the falling blocks)
- Glue or draw pictures of organisms onto the blocks. It can be helpful to try to pay some attention to the relative numbers of organisms (more producers than secondary consumers, etc.) although this is not strictly necessary.
- Students take turns placing blocks on the table, producers on the bottom, then secondary consumers, etc., spacing them an equal distance apart. Build an "ecosystem" by placing layer upon layer of blocks until a certain ecosystem size (complexity) is obtained.
- Now, the fun part...Students take turns removing blocks and making up a reason for that particular animal's (or plant's) removal from the ecosystem. For example, a block containing a picture of a clam could be removed because of extensive shell-dredging.
- Eventually, the "ecosystem" becomes less and less stable as blocks are removed. One of the remaining blocks will inevitably cause the "ecosystem" to crash...Great Fun! This can lead to many interesting discussions if students are guided through the many possible ecosystem concepts.
Alternate Suggestion: Place nothing but secondary consumers on the bottom layer and try to determine which of these animals is the "keystone species."
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