Improving science education is often regarded as a priority for developing countries in order to promote longterm economic development. Thus initiatives, both government and foreign-aid sponsored, aimed at improving science education in developing countries abound. However, all too often the focus of such initiatives is limited to the development of science curricula, while the details of how the curricula will be implemented at school level are often neglected. This paper represents an effort to lay the groundwork for a theory of curriculum implementation with particular reference to developing countries. We have drawn on school development, educational change, and science education literature in order to develop three constructs that could form the heart of such a theory, namely, Profile of Implementation, Capacity to Innovate, and Outside Support. Six propositions are offered to suggest how the constructs may inter-relate as a basis for the development of the theory. The implementation of the natural sciences learning area of the South African Curriculum 2005 is used to illustrate the emerging theory.

Many students enter physics courses with highly intuitive conceptions of nonobservable phenomena such as heat and temperature. The conceptions of heat and temperature are usually poorly differentiated and heat is often confused with internal energy. This article focuses on one student's cognitive and affective changes which occurred during the Grade 11 topic of heat and temperature. The instruction used an inquiry approach coupled with concept substitution strategies aimed at restructuring alternative conceptions identified using pretests. A constructivist perspective drove both the teaching and research, and Ausubel's theory of meaningful learning augmented the interpretive framework. The qualitative data comprising transcripts of all classroom discussions, student portfolios containing all of each student's written work, and teacher/researcher observations and reflections were collected and interpreted to generate a case study for one student named Ken. Ken's initial conceptual framework was undifferentiated with respect to heat and temperature. The course activities and concomitant use of concept substitution helped him differentiate these concepts and integrate them in a more scientifically acceptable way. A degree of affective and epistemological change was also identified as the course progressed. In-depth examination of the student's prior, formative, and final conceptions showed that during this unit, the student progressively accepted greater responsibility for his learning, was willing to take cognitive risks, and became more critical and rigorous in both written and verbal problem solving.

Diagrams are considered to be invaluable teaching and learning tools in biochemistry, because they help learners build mental models of phenomena, which allows for comprehension and integration of scientific concepts. Sometimes, however, students experience difficulties with the interpretation of diagrams, which may have a negative effect on their learning of science. This paper reports on three categories of difficulties encountered by students with the interpretation of a stylized textbook diagram of the structure of immunoglobulin G (IgG). The difficulties were identified and classified using the four-level framework of Grayson et al. [1]. Possible factors affecting the ability of students to interpret the diagram, and various teaching and learning strategies that might remediate the difficulties are also discussed.Keywords: Student's conceptual and reasoning difficulties, textbook diagrams, teaching and learning.Over the past three decades, a major focus of science education research has been the identification of the reasoning and conceptual difficulties of students. Furthermore, it has been shown that if such difficulties are not addressed they can hinder students' learning and understanding of science [2]. A large number of student difficulties have been reported in physics (e.g. see Ref.3), chemistry (e.g. see Ref. 4), and biology (e.g. see Ref. 5). In biochemistry, however, only a few such difficulties have been identified by formal research. Fisher [6], for example, has published research on student difficulties with protein synthesis, whereas Anderson and Grayson [7] and Anderson et al. [8] have identified a range of conceptual and reasoning difficulties in the area of metabolism. Recently, a methodological framework has been developed for the identification and classification of such difficulties [1].Research in various disciplines has shown that diagrams can be extremely useful for clarifying and integrating concepts, for the mental representation of text, and for the construction of useful mental models of abstract phenomena such as chemical structures and biochemical reactions and processes [9,10]. What has not, however, always been acknowledged is that the interpretation of diagrams is a highly cognitively demanding task [11] that can lead to numerous misconceptions and incorrect ways of reasoning that are very difficult to correct through conventional teaching methods [12,13]. Although extensive literature exists on the general use of, and difficulties with, diagrams in other scientific fields (e.g. see Refs. 14 -17), very few research reports have been published on the effectiveness of diagrams in the field of biochemistry. Nuñ ez de Castro and Alonso [18] have shown that textbook diagrams of enzyme-catalyzed reactions are often too simplified and exclude essential chemical steps, whereas Menger et al. [19] have reported that the presentation of micelle structure in texts can be misleading, especially when they are presented as "spokes of a wheel." Crossley et al. [20] have presented prelimina...

This research concerns the development and assessment of a program of introductory astronomy conceptual exercises called ranking tasks. These exercises were designed based on results from science education research, learning theory, and classroom pilot studies. The investigation involved a single-group repeated measures experiment across eight key introductory astronomy topics with 253 students at the University of Arizona. Student understanding of these astronomy topics was assessed before and after traditional instruction in an introductory astronomy course. Collaborative ranking tasks were introduced after traditional instruction on each topic, and student understanding was evaluated again. Results showed that average scores on multiple-choice tests across the eight astronomy topics increased from 32% before instruction, to 61% after traditional instruction, to 77% after the ranking-task exercises. A Likert scale attitude survey found that 83% of the students participating in the 16-week study thought that the rankingtask exercises helped their understanding of core astronomy concepts. Based on these results, we assert that supplementing traditional lecture-based instruction with collaborative ranking-task exercises can significantly improve student understanding of core astronomy topics.

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