Inquiry-based instructional strategies for effective conceptualization of photosynthesis: The case of elementary school

Abstract This study investigated the effectiveness of student-centered instruction on eighth-grade students’ conceptual understanding of photosynthesis. The study employed a Quasi-experimental research method. The data collection instruments included were multiple-choice tests, observations, and an informal assessment. The pretest and posttest were administered before and after treatment, respectively. An informal assessment was also administered before and after the intervention. Besides, the observation was conducted from the first day up to the last day of the intervention. The pretest and posttest data were analyzed using descriptive statistics and t-tests quantitatively, while data collected through informal assessment and observation were presented using narration. The findings of the pretest revealed that there was no significant difference between the mean scores of the two groups. Post-test results revealed that experimental group students significantly improved their conceptual understanding of the topic of photosynthesis compared to the control group students. The study concluded that the guided inquiry teaching method is more effective than the lecture method in improving students’ conceptual understanding of photosynthesis. Based on the findings of this study, it was recommended that governments encourage biology teachers to apply guided inquiry teaching methods by providing appropriate instructional material.


Introduction
Education is a process of active participation of students and teachers to achieve the goal of education by using different forms of work, strategy, teaching aids and media involvement. It enables individuals and society to make all-rounded participate in the development process by acquiring knowledge, ability, skills, and attitudes. Education is the main tool in the creation of human capital. It is the process of different activities. It involves refining, instruction, and exercises. The main aim of education is to evaluate all teaching and learning processes in every field of study (Audu, Ajayi, Angura et al., 2017). Selection of teaching method is one of the primary principles in education by taking into account the subject matter, the objective of the lesson, and the nature of the learner. Therefore, teaching students how to communicate effectively, cooperate with others, and learn independently has become the basics of education (El-Sayed et al., 2017).
Science education has become an integral part of a school environment; however, the process of teaching and learning science faces several challenges, including the idea of memorizing uncorrelated concepts, the lack of investigative activities, and the use of teaching method that does not give a chance for the student, and focus on the information as a crucial target (Qarareh, 2016). Qarareh also states that the application of educational principles and science subject should be connected in comprehending science teaching and learning in the classroom.
The quality of science teachers and the success of teaching science are the two sides of a coin in the teaching and learning process of science, and the main basic activity in science education is product, process, and scientific attitude, not just formula and calculation (Audu, Ajayi, Angura et al., 2017).
Biology is one part of science that deals with plants and animals. It is one of the science subjects studied at the primary school level in Ethiopia. Biology teaching and learning require the best teaching method to enhance students' participation and conceptual understanding (Nkechinyere & Mumuni, 2018). Teaching methods are the several ways in which knowledge, skills, etc. are inculcated in a teaching-learning process, through the guidance of the teacher and the application of an appropriate instructional method giving rise to an enriched learning environment and imperative outcome (Ajaja, 2013).
The main cause for this research is the fact that in our teaching practice successful application of innovative learning and teaching methods is extremely rare, which is especially the case in teaching the area of natural science, or, more precisely, biology subject. In biology subject, the teaching method affects the cognitive ability and classroom participation of students in the teaching-learning process. It increases their interest to do further investigation or activities, and it also makes students become independent learners who can use different sources of knowledge. Kalman et al. (2017) stated that there are different types of teaching methods that are commonly used in science education. These methods include the inquiry method, lecture method, demonstration method, project method, and so on.
The inquiry teaching method is an active learning method, which is learning by doing. In this type of teaching method, it is supposed that the teachers should be viewed as guidance, while students should be viewed as the knowledge maker rather than a passive listener (Dorgu, 2015). An inquiry is a process of understanding concepts by individuals through the process of conducting experiments and finding additional information through investigation and finally, that individual start to observe associations or patterns. In inquiry-based learning, students become engaged in many of the activities that scientists apply to construct new knowledge, and this inquiry-based learning is important for learners in order to accomplish their objectives.
In fact, teaching of biology requires making necessary provisions for students' active participation in the learning process, but in many schools, there is a gap in the teaching and learning process of biology. The researcher understands the gap from my experience when I taught biology for 6 years from Kon secondary school I usually adopt the lecture method. However, the method has not allowed for better conceptual understanding by students, and many students have a common misconception about the topic photosynthesis, like plants can take their own food from the environment in the form of air and minerals. The traditional teaching method is also known as the "chalk and talk" method, which is one of the teaching methods in which the teachers transfer the information verbally to the students. This teaching strategy does not enhance students' academic achievement, does not promote students' higher level of thinking, and reduced student participation since students remain passive in the lesson (Achimugu, 2018). But, according to the study by Nisa et al. (2018, March) in the constructivist theory of learning, students must participate in the teaching-learning process in order to construct their own knowledge and to understand the theory. That means in this theory of learning students are supported as to investigate, discuss, and interpret knowledge by themselves.
Literature has revealed that in biology subject, photosynthesis is a very challenging concept, and it is difficult to understand simply by learners. Eke (2016) noted that the concept of photosynthesis is a very abstract concept for students because of its biophysical and biochemical nature. Therefore, it requires the implementation of innovative teaching and learning methods. The study by Skribe Audu, Ajayi, Angura et al. (2017) revealed that at any school level, all students learn about photosynthesis by lecture learning method. Consequently, students face many difficulties in understanding the concept of this fundamental process. Researchers also showed that students have many misconceptions in relation to photosynthesis. For example, as stated by Kele and Kefeli (2010), students cannot understand the concept of photosynthesis because they have some misconceptions like plants do not do respiration (when, in, fact plants can do respire), carbon dioxide is harmful to plant (but, in fact, carbon dioxide is important to plant as raw material for making glucose) and the main role of sunlight for the plant is to make plants more attractive in color. In the other study, many students have common misconceptions, and they believe that plants get their food from the soil. In addition to these students also have other misconceptions like plants get their mass from the soil (O'Connell, 2008). Therefore, to overcome these problems, mentioned above from researchers' finding and experience, there is a need to strike a balance of effective teaching methods for biology subjects especially for photosynthesis, such as guided inquiry method of teaching. Regarding this method, many researchers carry out studies on photosynthesis by using guided inquiry teaching method. For example, Eke (2016), states that a guided inquiry teaching method is more effective to improve the conceptual understanding of students about photosynthesis and facilitating students" academic achievement. Guided inquiry learning in photosynthesis is very successful and valid because it can increase the practical ability of students and develop their conceptual understanding of the concept of photosynthesis. Guided inquiry teaching method plays an important role in developing student-centered approach and to improve students" conceptual understanding of photosynthesis. Thus, I hope this study can solve the problem mentioned above as well as to answer the basic research questions for this study.

Conceptual framework of the literature
The study is modeled by a conceptual framework that depicts a representation of dependent and independent variables and the relationships between them as shown by arrows in Figure 1. In this conceptual framework (See Figure 2), the teaching method and students' conceptual understanding are the two main variables. It is supposed that the dependent variable (the students' conceptual understanding) might be affected by the independent variables (the traditional teaching method and the guided inquiry teaching method) and would improve after the treatment by developing appropriate or effective teaching method. In other words, if the teacher is to take an effective teaching strategy, then the students have to improve their conceptual understanding. This study claims that the implementation of guided inquiry teaching method significantly improves the conceptual understanding of students than the traditional teaching method.
The main objective of this study was to investigate the effect of using guided inquiry teaching method in improving eighth-grade students' conceptual understanding of photosynthesis.

Specific objectives
• To examine the effect of using guided inquiry teaching method in improving students' conceptual understanding of photosynthesis.
• To assess the significant difference in the test scores of students taught with guided inquiry and lecture methods about photosynthesis?
• To observe the engagement of students when they are taught by a guided inquiry teaching method.

Research questions
The following research questions are formulated to guide the study: (1) What is the effect of guided inquiry teaching method in improving students' conceptual understanding of photosynthesis?
(2) Is there a statistically significant difference in conceptual understanding between the control and experimental groups?
(3) How is the engagement of students when they are taught by guided inquiry teaching method?

Null hypothesis
The following null hypotheses are formulated for testing at p ≤ 0.05 level of significance.
Ho1: There is no significant difference between the pretest mean the scores of experimental and control groups used for the study.
Ho2: There is no significant difference between the mean score of biology students conceptual understanding when exposed to guided inquiry teaching and those taught with traditional method.

Materials and methods
Research design serves as a blueprint for conducting a study. It describes the settings under which the study is to be conducted and how the data is to be generated, collected, and analyzed to answer the research questions. To address its research questions, the study predominantly adopted a quasi-experimental study. More specifically, a quasi-experimental study with posttestonly control group design was chosen as a method of inquiry. In a quasi-experimental design, intact groups are assigned into control and experimental groups when randomization of participants is not possible for some reasons. Random assignment of the treatment condition within intact classes increases both internal and external validity. Furthermore, a quasi-experimental design makes it possible to conduct evaluation studies in natural classroom settings. However, group comparability should be ensured at the beginning of any experimental study.

Study variables
The study involved the method of instruction as the independent variable and participants' performance on conceptual and procedural understanding tasks as the dependent variable. A variable being manipulated to cause some variation in another variable is the independent variable. The dependent variable is the variable being influenced upon the manipulation of the independent variable. On the other hand, the independent variables are the guided inquiry teaching method and the traditional teaching method. The dependent variable is students' conceptual understanding of photosynthesis.

Validity and reliability
Validity addresses whether the instrument measures what it claims to measure. Construct validity refers to how well the test items made up of the measuring instrument reflect the characteristics of the constructs being measured. Construct validity requires the construction of test items in ways that adequately reflect the characteristics of the constructs that elicit item responses. The constructs of conceptual biology understanding were operationalized through the test items. Construct validity of the test items was checked against the theoretical characterizations anchored to a review of the literature on measure construction of conceptual and procedural knowledge in biology. Two senior biology teachers independently classified the test tasks as conceptual tasks, procedural tasks, or undecided as to which construct each item predominantly reflects characterizations of the conceptual understanding, procedural understanding, or undecided. The test items for which the coders were found ambiguous were discarded. To test the reliability of the measuring tool conducted using trial testing, piloting it on one of the governmental schools called Ewket Fana Primary School in a similar setting of the sampled schools. The selected school was similar to those that featured in the main study in terms of location and status. Similarly, these selected students are similar to the subjects of the study with respect to age and exposure to instructional resources and learning of the biology subject.

Source of data
In order to investigate this research, the researchers used eighth-grade students as a source of data from Dill Chibo Primary School. The population of the study consisted of eighth-grade students in dill chibo primary school. The total population is 217 students out of which 101 were male students and 116 were female students.

Sample and sampling technique
From the population of the study out of four sections with a total number of 217, two-section students with a total number of 101 were selected as a sample by random sampling technique or lottery system. These were assigned as 51 students for the experimental group (Male 24 & Female 27) and 50 students for the control group (Male 23 & Female 27). Then, the total sample population of this study was 101.

Intervention procedure
In order to investigate the effect of using guided inquiry teaching method in improving students' conceptual understanding of photosynthesis, the researcher conducted the intervention process for 3 weeks by preparing an intervention plan on the subtopic introduction to food manufacturing in green plants, how glucose is formed during photosynthesis, do all parts of variegated leaves carry out enough photosynthesis, the internal parts of the leaf, is oxygen a byproduct of photosynthesis, and does the intensity of the light affect the rate of photosynthesis. Before the implementation of the intervention, the researchers conducted the same pretest for both experimental and control groups at the same time in order to check the background of students about the concept of photosynthesis. After this, the researcher implemented the intervention process by preparing a lesson plan through 5E instructional design model to encourage students in each step for the experimental group. In this case, experimental groups were treated by the guided inquiry teaching method about photosynthesis, whereas the control groups were treated by the lecture method about photosynthesis by preparing the lesson plan.
Finally, after the implementation of the intervention, the researcher administered the same posttest for both experimental and control groups at the same time to assess the effect of the treatment. During the intervention process, the researcher collected data through observation and informal assessment from the first day up to the last day of the lesson.

Teaching approach for the experimental group
In the experimental group, the teacher-directed strategy was the guided inquiry teaching method. At the beginning of the lesson, the teacher arranged students in experimental classes into heterogeneous groups according to their grades in the first-semester biology final exam and asked engaging questions about the daily lesson to identify the misconception of students and to capture their prediction. Then, the teacher invited them to do activities or experiments through their own procedures within their group by asking inquiry questions in order to eliminate their misconception and to develop their conceptual understanding. At that time, the teacher helped students by giving suggestions or comments about their activity or their procedures as a facilitator. After this, the teacher also invited them to explain or reflect their findings from their experiment and gave feedback about their answer to the guiding questions. Finally, the teacher has evaluated students by asking several questions to check whether the students attain the intended objective or not and to recap the main concept of the daily lesson.

Teaching approach for the control group
In the control group, the teacher-directed strategy was used as traditional instruction, and the teacher used lecture teaching method to teach the concepts of photosynthesis. At the beginning of the lesson, the teacher invited students to read the topic of the daily lesson from their textbook within a group in their classroom. Then, after the teacher gave a short note and explained the concept of the daily lesson about photosynthesis. After the explanation of the concepts, the teacher demonstrated different activities and experiments related to photosynthesis that listed in the textbook. The demonstration was followed by the procedure listed in the students' textbook. During this time students observed the teacher demonstration and can ask questions if they have or if the demonstration is not clear. At the end of each lesson, the teacher asked several questions related to the demonstrations and the daily lesson, received students' responses, and explained the results.

Data gathering instruments
The data gathering instrument for this study were a conceptual understanding test (pretest and posttest), observation, and informal assessment. These data gathering instruments were used to collect adequate information from the participants of the study.

Conceptual understanding test (pretest and posttest)
This instrument was in the form of multiple-choice tests, which was drawn from the concepts of photosynthesis. The test was prepared by the researcher to investigate the effect of using guided inquiry teaching method in improving students' conceptual understanding of photosynthesis. The main purpose of the administration of pretest was in order to check the prior knowledge or the background of students about the topic photosynthesis. In other words, it was important to identify what students know about the topic photosynthesis before the intervention process. However, the main objective of conducting the posttest was to check the effect of the treatment or in order to compare the conceptual understanding of experimental and control group students about the topic photosynthesis. Both pre-and posttest were similar except for the color of the question paper or the orders of the question and the time of administration.

Observation
Observation is the systematic screening of people's actions, analysis, and interpretation of their activities. The researcher collected data during the treatment stage through observation from the beginning up to the last day of the lesson about students' participation, their interest towards the lesson and my teaching method, their interaction during the discussion, and so on by preparing observation checklist.

Data gathering procedures
As shown in Figure 3, different procedures were taken by the researcher in order to collect the necessary information for this study. First, the pretest was administered to the experimental and control group students at the same time. The main objective of conducting the pretest was to check the background of students on the topic of photosynthesis. After the administration of the pretest, the treatment lasted 3 weeks. The experimental group students were taught the photosynthesis concept using the guided inquiry teaching method, while the control group students were taught the same concept using the lecture method. At this time, the researcher has collected data through observation and informal assessment. At the end of 3 weeks of instruction, the posttest was administered for both experimental and control group students in order to compare the conceptual understanding of students in the experimental and control group or to assess the effect of the treatment. All the tests (i.e., pretest & posttest) were submitted to the researcher by the students immediately after the tests.

Method of data analysis
The data collected through pretest and posttest were analyzed using descriptive statistics and t-tests (independent sample t-test and paired sample t-test) through SPSS (Statistical Package for Social Sciences) software version 20 quantitatively, while data collected through informal assessment and observation were analyzed and narrated using narrative descriptions of words qualitatively.  The data collected through pre-and posttest were analyzed using SPSS (Statistical Package for Social Sciences) program version 20 in order to answer the first and the second research question. First, the results of the pretest and posttest were analyzed through descriptive statistics to find the mean and the standard deviation of the score of each group. Secondly, the pretest and the posttest were also analyzed through independent t-test in order to prove if there were significant differences between the experimental group and the control group. Third, both tests were also analyzed through a paired t-test to compare the mean score of pre and posttest in the same group. In addition to pretest and posttest, the first research question was also answered by assessing students through informal assessment (to check the conceptual understanding of students about the concept of photosynthesis). Data collected through observations were analyzed to answer the third research question. These qualitative data were analyzed through narration.

Ethical consideration
The researcher received a letter of approval from the Department of Teacher Education and Curricula Studies at Bahir Dar University to conduct the experimental study. Before the start of the experiment, the researcher visited the participating school and met with the principal to discuss the purpose and nature of the study. Following a brief discussion, the school administration granted permission to conduct the study. It was unlikely that there were any harm or discomfort associated with the participation in the study because the study did not affect or disturb the normal class schedule, and the main intention of the study was to maximize the process of learning by which the goals and objectives of biology teaching are achieved. As far as the knowledge of the researcher was concerned, ethical issues were respected during data analysis and interpretation and in writing and disseminating research findings.

Data Analysis and Results
This report indicates the analysis of the data collected through pretest, posttest, informal assessment, and classroom observation in order to answer the three basic research questions mentioned previously to achieve the objective of the study.

Descriptive statically analysis of pretest and posttest for both groups
The result in Table 1, shows that in the pretest, experimental group students recorded (maximum score = 6 & minimum score = 0) and the mean score of this group was 3.12 with a standard deviation of 1.532, while the control group students recorded (maximum = 7 & minimum = 0) and this group also performed the mean score of 3.24 with a standard deviation of 1.585. However, in the posttest (after the treatment) experimental group students recorded (maximum = 15 & minimum = 5) and this group also performed the mean score of 10.24 with a standard deviation of 2.605, while the control group students recorded (maximum = 12 & minimum = 3) and the mean score of 7.26 with a standard deviation of 2.311. This result showed that in the pretest both experimental and control groups perform approximately equal mean scores or they have the same background on the concept of photosynthesis but, after the treatment, the experimental group students perform higher mean score than the control group. This implies that the guided inquiry teaching method was an effective method to improve the conceptual understanding of students in the concept of photosynthesis.

Independent t-test analysis of pretest and posttest result for both groups
Table 2, shows that the independent t-test analysis of the pretest score for both experimental and control groups. The results of the t-test are presented as, the mean difference between the two groups was 0.122, the level of significance α value is 0.05, Sig. 2-tailed (P-value = .694) and t (99) = .395; P > 0.05. Since the P value is greater than α value, we have enough evidence to Not significant at P > 0.05 not reject the homogeneity of the two groups in the pretest that is the mean is approximately equal to a minimum mean difference. Therefore, this result showed that there was no significant difference between the mean score of the experimental and control groups in the pretest or before the treatment. Table 3 shows that the independent t-test analysis of the posttest score for both experimental and control groups. The result of the t-test is presented as, the mean difference between the two groups was 2.975, Level of significance α value = 0.05, Sig. 2-tailed (p-value = .000) and t (99) = 6.069; P < 0.05. Since the P value is less than α value, we have enough evidence to reject the homogeneity of the two groups in the posttest that is the mean is not equal to a wide mean difference. Therefore, this result showed that there was a significant difference between the mean score of the experimental and control groups in the posttest or after the implementation of the treatment. As a result, the experimental group students taught with guided inquiry method performed better mean score than the control group students taught with lecture method. This means that this significant difference is in favor of a guided inquiry teaching method.

Paired sample t-test for both group between pre-post test scores
As shown in Table 4, paired sample t-test was conducted to evaluate the effect of guided inquiry and lecture method on students' conceptual understanding of photosynthesis. The result of the paired sample t-test indicates that there was a significant difference in the mean score of both experimental and control group in their pretest and posttest in favor of posttest that means in the experimental group the mean increases from pretest (Mean = 3.24, standard deviation = 1.585) to posttest (Mean = 10.24, Standard deviation = 2.605). The mean difference between pretest and posttest is 7.118 with a 95% confidence interval ranging from 6.260 to 7.976. In this group at t (50) = 16.663; P < 0.05. The same to that in the control group, the mean is increased from pretest (Mean = 3.24, Standard deviation = 1.585) to posttest (Mean = 7.26, Standard deviation = 2.311). The mean difference between pretest and posttest is 4.020 with a 95% confidence interval ranging from 3.232 to 4.808. In this group at t (49) = 10.248; P < 0.05. Therefore this shows that there is a significant difference in pretest and posttest results in favor of the posttest. However, experimental group students recorded a higher mean score with 7.118 mean differences between preand posttest but control group students recorded relatively low mean score with 4.020 mean differences between pre-and posttest.

Discussion of results
The main objective of this study was, to investigate the effect of using guided inquiry teaching method in improving grade eight students' conceptual understanding of photosynthesis. To achieve this objective and to answer the following research questions, experimental group students were treated by guided inquiry teaching method, whereas control groups treated by lecture method to teach the concept of photosynthesis by the researcher.

What is the effect of guided inquiry teaching method in improving students' conceptual understanding of photosynthesis?
According to the pretest data results in Table 1, experimental and control group students had approximately equal mean score, and standard deviation with minimum mean difference, or they have the same background on the concept of photosynthesis but, after the treatment, experimental group students perform higher mean score than the control group. This implies that the guided inquiry teaching method was an effective method to improve the conceptual understanding of students in the concept of photosynthesis.

Is there a significant difference in the test score of students taught with guided inquiry and lecture methods about photosynthesis?
According to this table, the P value is .694 which is greater than the value of alpha (0.05). Therefore, we can conclude that there is no significant difference between the mean score of the experimental and control group before the implementation of the treatment. After the implementation of the intervention, which means experimental groups were taught by guided inquiry method of teaching and control groups were taught by lecture method, the researcher administered the posttest for both groups to see the effect of the treatment.
As shown in Table 3, the results of the posttest data revealed that experimental and control group students recorded different mean score and standard deviation, which means experimental group students recorded higher mean score than the control group students. This indicates that the two groups were not equivalent in the mean score of the posttest. This was also checked by using an independent t-test. In this result, the p-value is .000 which is less than the value of alpha (0.05). Therefore, we have enough evidence to say that there is a significant difference between the mean score of the two groups in favor of the experimental group. This clearly indicates that guided inquiry teaching method had a significant effect in improving students' conceptual understanding of photosynthesis than the lecture method.
According to Table 4 paired sample t-test was implemented in the same group in order to compare the mean score of the pretest and the posttest. The results of Table 4 show that in both experimental and control groups, there is a significant difference between pretest and posttest results in favor of the posttest. However, when we compare the mean score of the experimental and the control group, experimental group students recorded higher mean score with 7.118 mean differences between pre-and posttest but control group students recorded relatively low mean score with 4.020 mean differences between pre-and posttest. Because of this reason, experimental group students were more beneficial than control group students, in other words, guided inquiry teaching method was more effective than lecture method in improving the conceptual understanding of students in the concept of photosynthesis.
In general, the result of the effect of using guided inquiry teaching method in improving students conceptual understanding of photosynthesis in grade eight biology class at Dill Chibo Primary School showed that there is a significant difference in the mean scores of students taught the concepts of photosynthesis using the guided inquiry and lecture methods. Students taught through guided inquiry teaching methods recorded better mean scores than those students taught through lecture methods. Since the pretest results in experimental and control group produce relatively equal with a very small difference in the recorded mean score, but the posttest results produce a wide mean difference between the two groups. This difference was due to the effect of the treatment. This indicates that the implementation of guided inquiry teaching method was more effective in improving the conceptual understanding of students in the concept of photosynthesis than the lecture method. This result is in line with the finding of Eke (2016), who investigated the effects of guided inquiry instructional and cooperative instructional strategies on students' academic achievement in conceptual understanding of photosynthesis and this study showed that guided inquiry teaching method is a more successful method than the conventional lecture method. Furthermore, this result is also inline with the finding of Almuntasheri et al., (2016). The findings of these researchers revealed that students who were treated by a guided inquiry teaching method had a better conceptual understanding of the lesson than other students who had been taught the traditional teaching method. In addition, the study by Nbina (2013), Nworgu and Otum (2013), and Ugwuadu (2010) found that guided inquiry teaching method is more effective in improving the performance of students than lecture method as this study also showed.
The results of this study show that students have a misconception on where do plants get their own food. They believe that plants get their food from the soil. Another misconception students obtained from the informal assessment was that plants get their own mass from the soil, and sunlight is important to plants in order to germinate the seed. This finding is supported by O'Connell (2008). According to this researcher's finding, students often believe that plants and trees get their mass from the soil. In addition to this, the result of this informal assessment also revealed that some students had a misconception about carbon dioxide, they said that carbon dioxide is produced from industry, cars and burning forests so, it is not important to plants rather it is harmful to plants. This result agrees with that of Kele and Kefeli (2010), who revealed that students cannot understand the concept of photosynthesis because they have some misconception, like carbon dioxide is harmful to plants.
After the misconception of students has been elicited and identified, the next procedure was the reconstruction of students' misconception through different teaching strategies in the intervention process. That means experimental group students were treated by the guided inquiry teaching method, while the control group students were treated by the lecture method. After the intervention process, the researcher also asked four open-ended questions to both groups. As shown in the result obtained from post-informal assessment, most students in the experimental group eliminate their misconception that appeared in the pretest. According to Kestler (2014), inquiry-based teaching is one of the successful teaching strategies to develop conceptual understanding and to eliminate students' misconception in science, especially in photosynthesis. However, in the control group, most students could not eliminate their misconceptions and they also could not improve their conceptual understanding. The results of these researchers revealed that teacher-centered teaching method and textbook-based instruction fail to improve students' conceptual understanding of the concept of photosynthesis and cannot change the misconceptions of students.

What is the engagement of students when they are taught by guided inquiry teaching method?
According to the result of observation data from the beginning of the intervention the researcher observed that many students in the guided inquiry class were passive in their participation, they were not confidential when they reflect their idea and when they do different activities by their own with minimum guidance, they had less reaction with each other, their interest was less for discussion and their discussion habit also not well. But, when the intervention process was going on those students showed a change gradually about their reaction in the classroom to do different activities. This classroom observation result revealed that many students were interested and actively participated, and they had a good reaction with their peers to do experiments and to discuss on the given problem when they taught about photosynthesis through guided inquiry teaching method. This finding agrees with the finding obtained by Achimugu (2018), who found that many students were very interested towards the guided inquiry teaching method, they were very eager or actively participate to do different activity or experiments within a group through a discussion on photosynthesis concept. Other results obtained from observation data showed that students who were taught by guided inquiry teaching methods became confidential through time to time when they performed different activities or experiments and when they reflected their ideas about the given problem by using the results from their investigation as evidence. This finding is supported by Audu et al. (2017), they described as through guided inquiry students increase their confidence and to develop a deep understanding of concepts. However, the data obtained from classroom observation in the control group students who were taught by lecture method revealed that most students in this class had less participation and interest rather they were passive listeners, their interaction during the discussion is not good. Muhammad et al. (2016) stated that lecture method is important to students by increasing their listening skill to attend attentively what the teacher says, however, the method also affects student participation as it makes them too passive listener.

Contributions and implications
The study has contributed to current research on effective teaching practices in several ways by demonstrating guided inquiry-based instruction as an alternative way of teaching biology for developing students' biology understanding. It adds empirical evidence to the field of knowledge of teaching approaches that student-centered teaching has led to an increased conceptual and procedural understanding of science topics. The evidence may be used to extend the understanding of the link between students' participation in classroom practices and their biology learning. It also provides an exhaustive literature review to readers with a concise list of scholars that have engaged in the research topic investigated and researchers of similar studies have a starting point. Among the contributions is an intervention manual that may assist teachers in designing and facilitating student-centered lessons in their classes.

Major findings
What is the effect of guided inquiry teaching method in improving students' conceptual understanding of photosynthesis?, Is there a significant difference in the test scores of students taught with guided inquiry and lecture methods about photosynthesis.
What is the engagement of students when they are taught by guided inquiry teaching method?
The findings of the pretest data revealed that both experimental and control group students perform approximately equal mean scores, which implies that they have the same level of understanding about the concept of photosynthesis before treatment. However, the posttest results show that the experimental group students taught with guided inquiry teaching method could perform a higher mean score than those students who were treated by the lecture method. The data obtained from pre-informal assessment result also showed that both experimental and control group students had a misconception about the concept of photosynthesis, but after treatment, most students in the experimental group could eliminate their misconceptions and could explain the open-ended questions in a better way than control group students. The results of observation data also showed that experimental group students were interested towards the guided inquiry teaching method, they became confident, and they were more eager to participate than the control group students. Therefore, the findings of this study showed that guided inquiry teaching method is an effective teaching method in improving students' conceptual understanding of photosynthesis than the lecture method.

Conclusion
It is concluded that the application of guided inquiry teaching method has a significantly different effect in improving students' conceptual understanding of photosynthesis compared to the application of the lecture method. Thus, the application of guided inquiry teaching is more effective in improving students' conceptual understanding of photosynthesis than the lecture method. The result of the study also showed that guided inquiry teaching method is important to students, not only in improving their conceptual understanding but also to increase their investigative skill, to be an independent learner, to motivate the participation or confidence of students, and to increase the reaction of students in the class with their peer to do different activity than the lecture method. The guided inquiry teaching method is an activity-based; learner center and teacher guided teaching method. Because of the result and activityoriented nature of guided inquiry teaching method, it can increase the interest of students to give more attention to the lesson.

Recommendations
Based on the findings of the study, teacher professional development programs and curriculum materials should incorporate student-centered strategies for the improvisation of student learning outcomes. The enhancement of students' understanding of photosynthesis concepts instruction can be improved by incorporating guided inquiry activities in school biology textbooks and teachers' professional development training programs. For instance, future research studies may also investigate the impact of an attempt to help teachers design and implement guided inquiry-based instructions in their classes. It would be highly invaluable if other researchers conduct longitudinal studies to explore the relationship between conceptual understanding and procedural understanding in a specific domain of biology in primary schools and to examine how guided inquiry-based instruction affects the relations between conceptual and procedural knowledge. Such studies would be useful to draw an extended discussion about the effectiveness of student-centered instruction in primary schools and higher education institutions and link the learning outcomes to changes in students' science behaviors.