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Prairie: Dynamic Ecosystem
Purpose: To encourage students to consider relationships
between different components of prairie ecosystems, and to
understand how changes, natural, or anthropogenic (human caused)
affect the individual organisms or populations of organisms in the
system. This acitivity can also form the basis for a writing
Materials: Several sets of cards or lists made by teachers or students:
Impact cards- Plants
Impact cards- animals
Methods: The cards/lists are simply a means of motivating students to organize their thoughts and consider the impact that different activities have on the web of life. Following a discussion, each student chooses an action and is asked the possible impacts on the ecosystem. A written essay may be required. When a student considers fire, for example, he/she should understand that fires are largely anthropogenic (historically), and that they are crucial in the maintenance of the prairie. Besides preventing the encroachment of shrubs and trees on the prairie, an autumn burn will reduce the litter, thereby affecting mammal polulations, and exposing the soil surface to greater sunlight and subsequent warmth in the spring which may cause early germination of specific prairie plants. For each activity, initial impacts on plants and animals should be considered. Next, the secondary changes in populations, etc., arising from an initial activity should be considered. A fire, for example, might reduce litter density, resulting in changing small mammal populations and availability which will affect (secondarily) the raptors that feed upon them.
Actions such as highway construction, land clearing, and development in general, all result in habitat fragmentation, which has a devastating effect on many species of grassland birds and other animals. Different land use patters can also change relative popluation sizes among organisms, favoring one type over another, eventually leading to decreased diversity. If a particular plant is eliminated, then a stem-boring nymph that feeds only on that plant will also disappear. The organisms that feed on the nymph or adult of that species may be affected and so on.
This exercise can be used in an interdisciplinary context. It is appropriate in the language arts classroom as well as the science classroom. Scientific literature on prairies can be supplemented with literature that covers or touches upon ecological topics.
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