Table 1 Selected examples of students’ written explanations of evolutionary change and corresponding human scores from the training set of EvoGrader
Normative Scientific idea | Non-normative Naive idea | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Student’s responses to ACORNS or ACORNS-like items | Variation [V] | Heredity [H] | Competition [C] | Limited resources [R] | Different survival [D] | Non-adaptive idea [NA] | Need/goal [N] | Use/disuse [U] | Adapt/acclimation [A] | Reasoning model type |
An elm tree may have had some seeds that were shaped a little differently from the others [V], which allowed them to land on the ground farther away from the parent tree. Those seeds may have germinated and sprouted better than the traditionally shaped seeds [D] because they didn’t land right under the parent tree and then had to compete [C] for nutrients and sunlight [R]. If the shape of winged seeds was genetic, those seeds could pass those genetic changes on to the seeds they produce [H]. Over long periods of time, natural selection selected for those seeds that were more wing shaped [D], until all of the seeds that successfully grew to adults all were wing shaped. | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | Pure scientific model |
The birds may have colonized a new area where predators are absent [R]. So the wings no longer provided an advantage in terms of escaping predation. At the same time the birds may be exploiting new sources of food in the water. Any mutation [V] that allowed the wing to successfully function more like a flipper would be advantageous (even if it had a deleterious effect on flight). These birds would have higher reproductive success [D]. If the mutation is heritable [H] it will increase in frequency in the population until it becomes fixed. | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | Pure scientific model |
The cacti without spines had to have developed spines over time [A] due to changes in its environment such as to prevent itself [N] from harm from other threats [R]. This trait of having spines therefore became favorable [D] and the trait will be passed down by generation to the next offspring and so on [H]. Therefore, the cacti today all have spines. | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | Mixed model |