Compare the Illustration View and the Chart View of carbon flows into and out of the atmosphere. Why is it helpful to see two different models to explain the same situation?

Many younger students think of models as either toys or simple copies of reality. This is broadly consistent with the everyday meaning of ‘model’ (e.g. ‘model cars’, ‘model airplanes’, ‘model railways’). Students often think of models as useful because they are copies (or even scale reproductions) of actual objects or actions. In such cases, students rarely look beyond the surface similarities between the model and the object or idea being represented by the model (that is, the question, 'Does it look like X?' will be the way the value of a model of X is judged).

As with many areas of science, the science meaning for the term ‘model’ differs from the everyday usage of the word. This is important in understanding student everyday experiences with models.

increase soil erosion                                             reduce soil erosion

cattle grazing                                                         hydroseeding

deforestation                                                         contour plowing

                                                                                planting vegetation

plant roots basically hold the top soil

together and stop soil erosion because

in such situation top soil is not removed

during flood but cattle grazing causes

soil erosion because cattle consume the

grasses and herbs and top soil is exposed.

same situation occurs because of

deforestation, the trees and plants are cut

down to expose top soil which causes soil

erosion

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