Organizing information scientifically is one of the four functions of science texts (Veel, 1997). In order to introduce organized scientific information science texts widely utilize ‘kind-of/part-of’ discourses. By such discourses, variety of part-whole and taxonomy relations among science objects can be described and then defined denotatively or connotatively (Copi & Cohen, 1994).

These relations could be stated along a spectrum from explicit to implicit. For instances, ‘Glucose is one kind of carbohydrate’ and ‘The nucleus, the central part of the atom…’ state the kind-of and part-of relations between objects directly. On the contrary, ‘… when blood is filled with oxygen carrying hemoglobin, the blood is bright red (oxygenated blood)’ and ‘Materials that are inflammable in daily life, such as charcoal and eradicant…’ indicate objects relations implicitly. Other types of discourses, such as ‘Blood is composed of blood plasma and blood cells’ and ‘Blood cells are divided into red blood cells, white blood cells and platelets’, locate at somewhere between these two extremes.

The semantics of kind-of and part-of discourses are not obvious. This is not only true for those discourses located at the implicit zone of the spectrum, it also holds even for the case of explicit discourses. Statement of ‘A is divided into B and C’ could be interpreted as a kind-of relation, such as ‘Globulins are divided into alpha, beta and gamma globulins’; or as a part-of relation, for instance, ‘The plant body is divided into a root system and a shoot or stem system.’

The relations among the whole and its parts are varied (Winston, 1987; Gerson, 2000). To understand a text readers have to figure out the embedded relations between objects stated in that text.

 

The purposes of this study aimed to investigate students’ semantic understanding of kind-of and part-of discourses of science objects described in science texts, and to explore their perceptions of science object if its constituents changed.

 

A blood text of current junior high science textbook was excerpted as the target text:

This text comprises of five sentences, 157 Chinese characters, and 13 events (clauses) according to the Transitivity analysis (Unsworth, 2001).  Although the text seems to be rather short, it consists of as complicated structure as seven layers of conceptual relations. The relations embedded in this structure include attribution, part-whole, and super-sub classes.

Based upon the blood text and the characteristics of part-of and kind-of discourses mentioned above, a twenty five items instrument was developed. The instrument covers five categories: attribution, kind-of relations, part-of relations, differentiation of ‘part of’ and ‘a part of’, and the resultants of changing the proportions of science object’s components. All items were constructed according to the following guidelines: changing part-of discourses of the blood text into kind-of discourses, and vice versa; rewording implicit part-of/kind-of discourses as explicit ones, and vice versa; and considering the features of Mandarin.

        Totally 329 subjects participated in this study. They are 142 7^th graders, 149 9^th graders, and 38 pre-service and in-service science teachers. All participants were asked to read the blood text and then answer the questions. Referring to the blood text was permissible while responding the test items. The reliability (λ₅) is 0.76.

 

        Major quantitative findings of the present study were summarized as following (qualitative findings were presented in full paper). Firstly, for the {c} sentence of the target text, more than 94% of subjects accepted it as ‘A red blood cell is a kind of blood cell’; as many as 69% participants accepted it as ‘White blood cells are a part of blood cells’; meanwhile, 61% and 95% of students accepted ‘Blood cells are composed of red blood cells, white blood cells and platelets’ and ‘Blood cells have red blood cells, white blood cells, and platelets’, respectively. Similarly, students also inclined (more than 81%) to interpret sentence {a} as ‘Blood is divided into blood cells and blood plasma’.

        The proportion or absence/presence of the components of an object affects readers’ perception of that object. About 84% readers accepted that it remains the same object when half of one of its components was removed; the acceptance rate was reduced to less than 20% as that component was removed. This suggested that readers inclined to interpret the part-whole relation described in the blood text is closed to the ‘ingredient/compound’ relation of Winston’s taxonomy of part-whole relations (1987), or the ‘compositional’ relation of Gerson’s (2000) framework.