Teaching enzymes to pre-service science teachers through POE (predict, observe, explain) method: The case of catalase

Descriptive research method was used in this study. Descriptive research aims to define, explain, clarify, and evaluate a situation in detail and reveal the relationships between events. Descriptive research only handles the existing events without changing anything in the studied environment and natural conditions (Çepni, 2007; Sönmez and Alacapınar, 2013).

Sample

38 second grade pre-service teachers attending Uludag University Faculty of Education Department of Science Teaching and taking the “General Biology Laboratory” course participated in this study which was carried out in the spring semester of the 2014-2015 academic year.

Data Collection Tool

Four worksheets prepared by the researchers based on the POE method entitled “The Effect of Catalase”, “Catalase Concentration”, “Relationship between Catalase Concentration and Surface Increases in a Liver Piece”, and “Can Catalase Be Re-used?” were used for data collection. The worksheets were prepared based on literature review and target behaviors on the subject of enzymes indicated in 2013 Secondary Education Biology Course Instructional Programme as well as Faculty of Education Department of Primary Education Science Curriculum. Every worksheet consists of three parts (i.e. predict, observe, and explain) and open-ended questions under these parts. The opinions of one biology professor and two science education experts were taken in order to check the content validity of the worksheets and determine whether or not the questions in the worksheets were clear, understandable, and suitable in terms of face validity and whether or not they contained any statement whose power of representing the studied subject and content validity had to be increased or which was unnecessary or unclear and had to be corrected.

Implementation

Three different teaching materials composed of the worksheets prepared based on the POE method, description of how to do the experiment, and explanation of the subject were distributed to the students before each activity. Based on these materials, the students were requested to fill in the sections related to predict, observe, and explain stages that were provided in the worksheets in detail. In the predict stage, the students were asked to write down their predictions about relevant subject together with their reasons before the experiment was carried out. In the observe stage, they were asked to carry out the experiment and record observation results. In the explain stage, they were asked to explain whether or not their predictions were consistent with their observation results together with their reasons.

Data Analysis

Firstly, the worksheets of the participants were enumerated from 1 to 38, and their descriptive analyses were made. The main aim in descriptive analysis is to reach concepts that can explain the data and the relationships between concepts. Thus, the data that were similar to one another were brought together within the framework of specific concepts and categories. Then they were put in order and interpreted. In the observe stage, most of the pre-service teachers were able to identify the points they were expected to see. The answers given in the predict and explain stages were evaluated and categorized. Frequency (f) and percentage (%) values were taken into consideration during data analysis. Table 1 shows the categories related to the predict stage and the explain stage and the contents of these categories.

Table 1. The Categories Used in Analyzing the Questions Included in the Predict and Explain Stages and Their Contents

Stage	Category	Content
Predict	Correct prediction	An answer that contains all aspects of the valid answer.
	Partly correct prediction	An answer that contains one aspect of the valid answer, but not all aspects.
	Incorrect prediction	Irrelevant or unclear answer; no answer; answer like “I do not know”, “I do not understand”.
Explain	Prediction and observation are consistent.	Expectation is consistent with what is observable during the experiment or the activity.
	Prediction and observation are partly consistent.	Expectation is partly consistent with what is observable during the experiment or the activity.
	Prediction and observation are inconsistent.	Expectation is inconsistent with what is observable during the experiment or the activity.
	No answer	-