They are maintained by the perpetuation of these conditions combined with the effects of periodic wild fires, droughts, and grazing animals. See The Tallgrass Prairie in Illinois . The plants associated with a tallgrass prairie are those which have evolved features suited to this combination of elements. Deep roots, for instance allow plants to tap ground water in times of drought.
Rhizomes allow plants to survive the periodic fires, which prevent trees from taking over.
As the season progresses and the grasses grow taller, different forbs come into flower at heights parallel to the height of the grass. These and others are examples of plants' adaptations to the conditions that form and maintain a tallgrass prairie. See The Tallgrass Prairie in Illinois . In this lesson, students are asked to consider changes in prairie conditions and the survival of prairie plants. Read about the mechanisms that drive evolutionary change in Introduction to Evolutionary Biology and Observed Instances of Speciation .