טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentHagay Galit
SubjectHigh School students' Conceptions Related to Speciation
and Common Descent
DepartmentDepartment of Education in Science and Technology
Supervisor Ms. Luli Stern


Abstract

Two essential ideas are brought forth by the evolution theory: natural selection that explains the diversity of living things and the idea of common descent that explains the similarity within that diversity. While many studies have focused on the learning and teaching of natural selection, few studies attempted to explore students’ ideas related to common descent. The objectives of the current study were to identify students’ conceptions related to common descent and speciation, and to examine the effect of a curricular unit that was based on these conceptions.

The ideas of 231 12th grade students from eight schools were characterized. Our findings suggest that high school students have difficulties appreciating the idea that new species are formed as a result of the continuing operation of natural selection on new characteristics and in different environments. Instead, many of the students maintain naïve ideas about how new species are formed. For example, students think that new species are produced (deliberately) by people or by the occasional reproduction of two existing species. Similarly, students hold alternative conceptions with respect to the idea that all organisms are related by common descent. For example, when asked to explain the similarity between humans’ DNA and chimpanzees’ DNA, only 13% of these students, provided a scientifically accepted explanation, that is that humans and chimpanzees share a common ancestor. Most students (73%) asserted that humans are a more developed step of chimpanzees. These students view evolution as a “ladder” in which the lower forms are all replaced by superior forms. When asked to explain the similarity between cells of humans and cells of potatoes, many students (63%) expressed other naïve idea, that all living things have to adapt to the same conditions and this is the reason for their similarity.
Students’ ideas characterized in this study served as the basis for the development of a curricular unit on evolution. The unit, which was based on the conceptual change model, was tried with 53 10th grade students. Our findings show that more than 50% of the students improved their understanding of the idea of common descent.
Given the major emphasis that is placed on the idea of common descent in the modern theory of evolution and in the secondary school curriculum, we believe that insights gained from our study can provide some helpful suggestions for curriculum development, science teaching, and research.