Table 2.

Model function rubric, developed for analyzing students’ models (midterm and final) for presence/absence of concepts regarding phenotypic variation and its genetic origin^a

1. The model explicitly represents variation at the genetic level (different alleles).

2. The model explicitly represents variation at the phenotypic level (different phenotypes).

3. Phenotypic variation is directly connected to genetic variation (e.g., there is a direct flow of information from alleles, or genotypes, to the corresponding phenotypes).

4. The model includes the concept of mutation (as a structure or as a behavior).

a. The concept of mutation is linked to appropriate molecular-level structure/s (nucleotides, nucleotide sequence, DNA, gene, and/or allele);

b. Mutation is appropriately incorporated (4a above is true) and is used to explain the origin of different alleles (e.g., mutation alters a gene sequence to cause the origin of a new allele).

^aItems 4, 4a, and 4b were also used to analyze students’ short answers about the origin of variation on the final exam.