The effects of Swedish Knife Model on students’ understanding of the digestive system

The main purpose of this paper was to evaluate the effectiveness of the Swedish Knife Model to overcome students’ misconceptions of digestion and the organs of the digestive system. According to the students’ pre and post-test scores, it can be said that the ratio of the students’ correct explanations to the questions increased in general after the teaching process. It is thought that teaching activities supported students in actively participating in the learning process and improved their learning. Before the study, the students had misconceptions and limited knowledge about ‘the definition of digestion’ (see Table 3). Students had defined digestion as ‘ingested food broken down into small pieces with enzymes or biting, in order to pass the cell membrane’, with no mention of ’chemical’ or ‘mechanical’ digestion. They also did not emphasize the chemical changes of the food after digestion. It was revealed that 4th and 5th grade students also described digestion as ‘nutrients broken into pieces’ (Teiexera, 2000; Cakici, 2005). After the application of teaching model, it was observed that the ratio of students' correct and partial explanations increased and misconceptions disappeared (see Table 3). During teaching process, the concept of digestion was generally defined; mechanical and chemical digestion was not explained in detail. It was thought that the ratio of students' partial explanations was increased through this definition.

When the replies of the students, relating to the starting and ending point of digestion, were examined before the study, it was ascertained that the students had misconceptions, indicating that digestion ended in the anus or large intestine. It was also determined that the same misconceptions existed amongst 5th grade students: these students also tended to believe that digestion occurred in the anus, as it was the last part of digestion (Cakici, 2005). After the activities, it was observed that the proportion of the students’ correct answers increased, while the ratio of the misconceptions decreased (see Table 5). It was supposed that the puzzle activity supported this situation.

When the findings of the pre-test, regarding the organs and the structure of the digestion system, were examined, it was ascertained that the students had misconceptions and missing knowledge beforehand. After the teaching process students’ misconceptions and the correct answer ratios increased significantly (see Table 5). The activities of the model, ‘what you’ve learnt’ and ‘cut and stick’, helped the students to reinforce their learning and eliminate any misconceptions. In their interviews, students indicated that they had great fun while doing ‘cut and stick’ activity, supporting the claim in the previous sentence: in the pre-test, the students had marked ‘pancreas’, ‘liver’ and ‘kidney’ in the digestive tract. Cerrah and Urey (2010) revealed that second-year students of primary school education teaching listed the kidney and liver amongst the digestive organs. This situation can be interpreted as an indication of the transportation of misconceptions to higher education grades, if unchallenged. It attracts attention to the fact that, if the misconceptions of teacher candidates are not challenged, such misconceptions will possibly be transferred to their students. Another reason for students’ misconceptions was confusion of the ‘excretion’ and ‘elimination’ concepts. Students use excretion instead of elimination, teachers also don’t mention waste product of digestion as elimination. Because ‘metabolism wastes’ and ‘digestion wastes’ are expelled from the body, students use excretion as synonyms of elimination (Güngör & Özgür, 2009). When the findings of the pre-test, regarding organs and the structure of the digestive system, were examined, it was apparent that most of the students correctly identified the organs in which chemical digestion occurred and stated the large intestine in their misconceptions. In their analogies, students made simulations stating that digestion occurred in the large intestine. After the study, it was observed that the ratio of correct answers decreased, whilst the ratio of misconceptions and the number of the students stating the large intestine increased (see Table 6). The students indicated that ’nutrients were broken into small pieces chemically by the liquid/acid secretion of these organs’. Similarly, young students stated that ‘nutrients were dissolved by the help of water, acid and liquid’ (Teixera, 200; Cakici, 2005).

Before the study, it was revealed that students had misconceptions such as ’mechanical digestion occurs in the esophagus, the liver and the small and large intestines’. After the study, the ratio of the students stating the small intestine increased, while the ratio of the students stating the large intestine decreased (see table 5). As a result of this, students stated that ‘fats are chemically digested in the small intestine. Some students stated: ‘in these organs, mechanical digestion occurs, as there is no enzyme’, while others stated that the reason mechanical digestion occurs in these organs was in order to facilitate chemical digestion. Although the purpose of the large intestine was emphasized in the applied material, it was noted that students were reluctant to change their ideas. Similarly, it was very difficult to change students’ misconceptions regarding the mechanical digestion of fats in the small intestine. Before the study, the students had misconceptions about the liver, such as ‘it digests fats mechanically, it helps the stomach to digest, its helps the blood and it expels water and nutritional waste from the body as excretion’. After the study, it was observed that there was no significant changes in their ideas (see Table 5). With regards to the functions of the large intestine, before the study, it was observed that there were misconceptions and wrong answers. The students defined the liver as ‘filtering wastes and expelling them from the body’ and likened the large intestine to a sponge, as a result of its filtering function. Prokop and Fanéoviéova (2006) revealed that university students knew that it was the job of the large intestine to absorb nutrients. After the study, it was observed that the ratio of misconceptions and wrong answers were decreased (see Table 5).

When the analogies of the students were evaluated, it was revealed that the students formed simple metaphors, according to one aspect of the organs, and such metaphors allowed misconceptions to emerge. None of the students developed an analogy by paying attention to chemical digestion through the mouth; instead, they formed metaphors according to the shape of the small intestine and they stated that the large intestine ground waste and the stomach saved nutrients (see Table 7). We attempted to change these thoughts through discussions held in the classroom.

Despite treatment, some students were reluctant to change their misconceptions. In general, the Swedish Knife Teaching Model positively affected students' learning and had a positive effect in banishing most of their misconceptions. And also the process made science enjoyable for them; it was a different experience for the students. The findings of the interviews supported this situation. The activities in the model can be changed or some other activities may be added according to students’ and topic characteristics. It is suggested to applicators of this model to change the definition of digestion in the first activity by adding chemical and mechanical digestion concepts. Teachers should be give feedback the students’ answers in each activity part. Teachers need effective teaching activities, however they had no time to develop new materials. This kind of studies would be guiding for teachers.