In science education, the importance of understanding nature of science (NOS) has been emphasized for long years. For this reason, several research attempts has been made to increase the effectiveness of NOS instruction and improve learners' NOS understanding. Although the importance of NOS has been appreciated, there is no single definition of the term. The most commonly used definition of the term was made by Lederman (1992) as “the epistemology of science, science as a way of knowing, or values and beliefs inherent to the development of scientific knowledge” (p. 331). Moreover, NSTA (2000) suggested that all people involved with science should have a meaningful understanding of NOS and identified critical premises that should be known to understand NOS which can be summarized as:

1. Scientific knowledge is both reliable and tentative.
2. There is no single scientific method.
3. Creativity is a vital element during the production of scientific knowledge.
4. Science is limited to naturalistic methods and explanations.
5. Formation of theories and laws, which are interrelated but different concepts.
6. The existing scientific knowledge, social and cultural context, expectations and background of the researcher influence scientists' work.
7. New evidences and re-interpretations of the old ones result in changes in science.
8. Science and technology influences each other but practical outcomes are not the main concern of science.

However, recent studies still reveal that gaining learners a meaningful understanding of NOS is not an easy goal to achieve. Based on his comprehensive literature review of research of NOS, Lederman (2007) concluded that K-12 students and teachers generally do not have adequate understandings of NOS, explicit-reflective approach is better than implicit approach in facilitating NOS understanding, teachers do not necessarily translate their NOS understandings into their classroom practice, and teachers do not value NOS as an instructional outcome as they value traditional subject matter outcomes.

Although the studies related to NOS instruction and understanding is not restricted to science education and pre-service science teachers, the studies regarding the NOS understanding of other pre-service elementary teachers are very limited when compared to pre-service science teachers. Moreover, in teacher education programs in Turkey, only elementary science education program have a course related to NOS. Even though early childhood teachers also need to teach science in their future classrooms, they do not learn about NOS as well as elementary science teachers. As Akerson, Morrison and McDuffie (2006) suggested if teachers do not hold appropriate views of NOS themselves, they cannot teach appropriate views to students in their future classrooms. For this reason, it is important to teach NOS to the pre-service early childhood teachers if we expect them to teach science and NOS effectively in the future.

The purpose of the present study is to investigate whether pre-service science teachers and pre-service early childhood teachers differs in terms of their NOS understandings. The specific research question that guide this study is: "Is there a significant difference in PTs’ understanding of NOS by their departments?"

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