Academic journal article The American Biology Teacher

Tail's Inheritance: Challenging Secondary School Student's Ideas about the Inheritance of Acquired Traits

Academic journal article The American Biology Teacher

Tail's Inheritance: Challenging Secondary School Student's Ideas about the Inheritance of Acquired Traits

Article excerpt

Numerous studies have been conducted in the last two decades on students' conceptions regarding natural selection and adaptation. These studies repeatedly indicate that students of all ages--from middle school to college students--have difficulties understanding the notion of natural selection (summaries can be found in AAAS, 1993). Students', ideas are typically intuitive and consistent with their everyday life experiences. In everyday life, individuals adapt deliberately to changes in their environment by changing their form or behavior. Consequently, students explain a gradual change in populations in terms of deliberate change of individuals rather than inadvertent change in the proportion of individuals carrying advantageous traits in a population. Similarly, students may sometimes see that traits such as smoking or bodybuilding "run" in some families and intuit incorrectly that these acquired traits are inherited. Students' ideas are presented in Table 1.

The purpose of this article is to outline a lesson plan that is designed to challenge one commonly held naive idea, namely, the inheritance of acquired traits. While scientists believe that the experiences an organism has during its lifetime can affect its offspring mainly if the genes in its own sex cells are changed by the experiences, it was repeatedly found that many middle school students believe that experiences and traits acquired during an individual's lifetime can be passed on to its offspring (for example, Brumby, 1984; Clough & Wood-Robinson, 1985). This naive idea may in turn hinder the understanding of the theory of natural selection, leading to beliefs concerning the inheritance of environmentally induced characteristics over several generations.

In this activity, students express and defend their ideas, consider alternative positions, get feedback from the teacher and their peers, and eventually reach the sought conclusion. Therefore, the objectives of this activity are not only to address students' prior knowledge about the inheritance of acquired traits but also to provide opportunities for students to practice the way science knowledge is constructed. Driver, Newton, and Osborne (2000) advocated the emphasis of argumentation in the science classroom as it provides students with an authentic image of the reasoning involved in gaining confidence in scientific knowledge:

   ... if we intend to show the socially constructed nature
   of scientific knowledge, we must give a much higher
   priority than is currently the case to discursive practices
   in general and to argument in particular. Being
   able to present coherent arguments and evaluate
   others ... is important if students are to understand
   the basis of the knowledge claims with which they
   are confronted.

      Driver et al., 2000, p. 297

Curricular Context

The lesson plan described is part of a short curricular unit consisting of approximately 10-12 class periods. We tried it out with grades eight and nine, as well as with high school students and found this approach to be effective in creating an atmosphere that welcomes and rewards expression of ideas and classroom dispute. Moreover, following instruction, most students satisfactorily explain natural phenomena using the mechanism of natural selection.

This curriculum includes the following lessons:

   Lesson 1. How Do Populations Change Over Time?

      An introductory lesson designed to elicit students'
      ideas regarding the evolution of the giraffes' neck.

   Lesson 2. Are Acquired Traits Inherited?

      August Weissman's experiment is used to challenge
      students' naive ideas.

   Lesson 3. Why Are Some Traits Passed On to the
   Offspring and Some Are Not?

      Exploring examples of inherited and non-inherited

   Lesson 4. Are All Organisms in a Given Population

      Exploring variation among plants, animals, and
      humans. … 
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