Student misconceptions or alternative conceptions of scientific phenomena have become a point of focus in science education research. Cross-age studies are useful for describing the understanding about a particular concept held by students across several grade levels. The present research utilized 7th-grade life science students, 10th-grade biology students, and college zoology students to evaluate changes in student understanding of the concept of homeostasis. Responses from 100 students from each grade level were selected for analysis. Each student was asked to respond to a test packet consisting of a biographical questionnaire, two Piagetian-like developmental tasks, and a concept evaluation statement (CES). The CES was used to measure the students' understandings of the concept of homeostasis.

Understanding of the concept increased across grade levels, but that understanding was limited. Thirty percent of the college students indicated at least a partial understanding of the concept, while only 3% of the seventh-grade students showed partial understanding of homeostasis. Although the older students were more likely to offer a response to the CES, those responses were often errant. Thus, the number of students exhibiting misconceptions increased across the grade levels as the number of students responding to the CES increased. Certain errant notions concerning heart rate, breathing rate, temperature constancy, and perspiration were persistent across the age-experience continuum. A relationship was found to exist between development level and student understanding of the concept.