Biology is one of the subjects studied in secondary schools in Nigeria. Biology is the study of living things. Ghumdia & Adams [1] asserted that Biology is essential for many fields of learning contributing to the national economy such as medicine, agriculture, biotechnology, and nursing. Kessy & Irene [2] reported that learning Biology equips learners with knowledge and skills that help them to face challenges in society especially those related to common diseases, pollution, and genetics. Kessy & Irene [2] cited Kareem that Biology subject leads to self-understanding and to how the body works.

The study of Biology is imperative because it is a required subject in the preparation of the work force for the medical, paramedical, agricultural and other related professions. Especially, the contributions of the biologist are strategic in industries, crime detection, research, health and disease control, population control, agriculture and teaching.

Olagunju cited in Ojetola [3] stressed the importance of ecology, a major component of the biology curriculum, in environmental education, understanding of socio-cultural' surrounding and preservation of nature.  In   this regard, Biology is usually the   most   highly  enrolled   science   subject  at   the   Senior Secondary School Examination (SSSE) in Nigeria. 

The inquiry-based method allows students to interact with their surroundings and make them able to see the abstract phenomenon in a real sense. so, it facilitates a deep understanding of the scientific content rather than role learning or cramming [2].

The Senior Secondary School Biology curriculum is designed to serve the needs and interest of the students of a wide ability group. Consequent upon the introduction of the 6-3-3-4 educational system in 1985, the new curriculum recommended, among others, that guided discovery approach, resting on the activities of the pupils, be used in teaching. The expectation is that a successful implementation of the curriculum objectives based on recommended techniques will produce learners that are equipped with adequate knowledge, attitude and skills that would enhance performance, sustain their interest and consequently serve as the springboard for the nation's scientific and technological breakthrough. But contrary to expectations, the level of achievement among secondary school Biology students has remained abysmally low.

A variety of reasons have been advanced for the downward trend in students' under-achievement in public examinations. Osokoya [4] reported poor teaching methods, lack of qualified staff, inadequate facilities and textbooks, poor communication skills and dearth of the knowledge of certain concepts as contributory factors. In general, the poor level of performance of students in major examinations could be traced to government, examining bodies, the school, the teachers, the home and the subjects. It is often stated that no educational system can ever rise above the level of the quality of its teachers, and that the quality of a teacher is totally described by his effectiveness. Therefore, the teacher's role and strategies are critical to the successful implementation of any educational system. Studies have shown that effective teaching strategies can bring about positive attitude of students towards a subject [5-7]. Adeyemo asserted that students' academic performance can be influenced through the teacher's resourcefulness, interest in the subject area, attitude to work, creativity and interaction with the students.

Various instructional techniques are employed to pass on knowledge to students in the schooling process. These include, among others, lecture, discussion, individualized instruction/computer aided instruction, practical and excursion methods. However, teaching in Nigerian secondary schools is dominated by teacher-centered and lecture/expository methods. These methods of instruction are confined to transmitting information because they merely involve telling, reading and memorizing. According to Nwagbo [8], these methods have failed to produce Biology students who can reason critically and be able to transfer what is learnt to new but similar situations. Okebukola [9] noted, that poor development of competence by pupils in the areas of observation, drawing and identification of flora and fauna and features of biological specimens contribute to poor performance in Biology. Competences in practical and theoretical aspects of syllabus requirements in certain major areas are also identified as vital keys to success.

The inquiry method enables students inquire into a problem with a view to finding some answers or reasons why the problem exists. It is opposed to the traditional methods where the teacher takes a dominant didactic role delivering science interaction to students through lectures, demonstration and text reading.

Onanuga [6] demonstrated the advantages of the guided discovery method over other methods in the teaching of Agricultural Science. Similarly, Umoinyang showed that achievement in secondary school science subjects could be influenced by gender, cognitive style and attitude. It has been reported that there are sex differences in specific ability performance of students. Nkoyo [10] Okeke showed that women, were not only under-represented but their levels of achievement in the fields of science and technology were low compared to the males. Nwagbo [7] reported that the guided enquiry method produced the highest mean achievement score for the high-level scientific literacy group followed by the medium and low-level group respectively.

However, in spite of the above findings on the effect of different variables on students' achievement in science, it appears a lot still needs to be done to improve the achievement of students in Biology concepts, hence the rationale for the present study.

The Senior Secondary School Biology curriculum designed for the current 6-3-3-4 of education in Nigeria is expected to prepare students for the attainment of reasonable and functional scientific attitudes. The result obtained in this study could justify the use of the inquiry method over the conventional instructional strategy in the development of discovery capabilities and intellect by students. The study is also expected to be informative on the improvement of teaching and learning of Biology in secondary schools.

The aim of this study is to establish the extent to which inquiry method of teaching influences students' academic achievement in Secondary School Biology. If the teacher's method of teaching has been blamed severally for the inability of students to perform creditably in certain concepts of Biology [4-7], then it is necessary to find out empirically the effectiveness of an alternative method. Thus, this study seeks to know to what extent the inquiry method of teaching would help students in the understanding of one of the fundamental concepts in Biology, the cell theory, and consequently improve their achievement in the subject generally.

The cell is a living unit because it displays the characteristics of living things. Ndu et al. [11] reported that a number of activities are involved in the life-processes of the living cell. Therefore, its understanding is critical to the learning of such bio-physical processes as osmosis, diffusion, turgidity, plasmolysis, active transport and, mitosis and meiosis. In addition, an in-depth knowledge of the cell theory would make it easy for students to understand how cells demonstrate the characteristics of living things, such as feeding, respiration, excretion, growth, response to environment and reproduction.

The problem in this investigation therefore, is to examine students' learning outcomes in the cell theory, using the inquiry method. The moderating effects of gender and mental ability on students' achievement are also investigated. 

Research Hypotheses

The following null hypotheses (H₀) were generated in this study:

• There is no significant difference in the pre-test and post-test mean scores of students exposed to inquiry method when they solve problems in the cell concept.

• There is no significant difference in the post-test mean scores of students exposed to inquiry method of teaching and those exposed to lecture method when they solve problems in the cell concept.

• There is no significant difference in the post-test mean scores of male and female students exposed to the same inquiry method of teaching when they solve problems in the cell concept.

Review of Related Literature

Numerous researches have been conducted by educators and psychologists on how to improve teaching and learning. According to Nwagbo [7], educationists and researchers have come up with innumerable theories of instruction. Some of the theories are prescriptive while others are non-prescriptive. These theories, however, are mostly centered on two major schools of thought in the field of methodology, the child-centered and the teacher-centered approaches. Debor defined inquiry-based teaching (IBT) as a pedagogy in which the teacher’s delivers curricula content via inquiry-based activities and students develop an understanding of the content by participating in actual scientific inquiry.

Kinyota defined inquiry-based science teaching as the teaching process that comprises the methods followed by scientists when doing their studies. Blyth, inquiry-based learning is an approach in which students learn by discovery, hence facilitates a deep understanding of the biology concepts and enables students to engage actively in the learning process. Ghumdia & Adams [1] defined inquiry as the strategy of teaching in which learners seek information or knowledge of certain phenomena with minimal guidance from their teacher. According to Deboer inquiry method helps the preparation of future scientists because students normally experienced the usual but diverse ways scientists do to explore natural phenomena.

Wabuke et al. cited in Kessy & Irene [2] inquiry-based teaching develops among students 21^st century skills like collaboration, communication, and presentation skills.

Annan et al. [12] affirm that inquiry-based teaching has greater positive effects on students’ academic achievement. Martins & Oyebanji [13] examined the effects of the inquiry and lecture teaching strategies on the cognitive achievement of Integrated Science students. The study adopted a pre-test, post-test experimental design using 167 Junior Secondary School II students drawn from Demonstration Secondary School, Ahmadu Bello University, Zaria. The t-test statistics was used to compare the mean achievement scores of the experimental groups before and after treatment. These results showed that students who were taught with the inquiry method performed significantly better than those taught by the lecture strategy. The inquiry approach used in the study is pro- social, activity oriented and so encourages student-teacher, student-student, and student-material interaction. The lecture group members who had been rendered passive listeners in their class, were denied such rewarding and exciting experience.

One of the recommended contemporary teaching practices in the classroom today is the inquiry method. The inquiry method is a student-centered method of education focused on asking questions. It is a multifaceted educational approach to teaching through what the children know and what they want to learn [7]. 

The inquiry method is motivated by the recognition that good learning and sound reasoning are dynamic processes of inquiry and they do not emanate from the end product of static knowledge. Science is a dynamic process of investigation, not a static collection of inalterable facts.

Therefore, the inquiry-based learning entails teaching strategies patterned after the methods of science and provides opportunities for meaningful learning. In this method, students are encouraged to ask questions which are meaningful to them, and which do not necessarily have easy answers. Educators see this as an opportunity for students to complete exercises on their own while teachers allow them to figure out thoughts, ideas, and concepts for themselves. With the inquiry method of instruction, students arrive at an understanding of concepts by themselves and therefore the responsibility for learning rests with them. The teacher acts as catalyst, directing students' interactions, activities, and, discussion rather than being the bearer of all information. Inquiry-based education requires allowing students to discover information that is new to them as well as developing a good relationship between the teacher and the student. The rationale for the emphasis on inquiry is that students will be more interested in science if they are involved (actively) in doing science. The steps of inquiry lessons include the following:

Purpose

The teacher should tell the students what they will be learning about and the interesting implications of the lesson. There will be a pedagogical purpose for the teacher to explain to the students. For example, testing the growth of a bean plant according to different variables, the teacher would introduce the purpose of the activity as: to study the effect of light and gravity of the growth of a bean seed. The students would be asked to hypothesize about what effect gravity would have on a young bean plant? Do they think the plant would grow towards or away from the center of the earth? What effect might light have on the growth of the bean plant?

Hypothesis

In those activities where there will be a hypothesis, the students should always be expected to make their own hypotheses. This should be done in small groups (pairs), then in whole class discussion. Students should state their hypotheses in terms of the effect of one variable on another, and must be encouraged to justify their hypotheses.

Procedure

Once students have a clear idea of the purpose of the experiment or study, they should have some idea of how to find the answer.

Materials

Once students know what they plan to do, they can make a list of the materials they will need. Sometimes it helps to tell them what materials are available before they design their procedure. However, often the materials they need can be brought from home. If students are testing different kinds of food for starch and fat, they should be encouraged to bring some from home. Students are encouraged to write what they plan to do and to write a list of the materials needed.

Data

Students should carry out their experiment. Since they designed the procedure, they should know what data to collect and should have a plan to record their data. However, before they begin the experiment they should be reminded of all safety precautions.

Analysis

Again, students should know what they are trying to find. They might need assistance, in steering away from their affirmation bias, however.

Conclusion

When the students have finished their study or experiment, they must discuss the results with one another. They must find out who had the same results, which had different results, why the results might have been different. They must interpret the results according to their original question. The class discussion of the conclusion is the de-brief of the lesson. This is when the meaning of the lesson can be put into the context of the unit as a whole.

The study of cells is an academic discipline known as cell, biology or cellular biology or cytology. Cell biology studies the physiological properties of cells, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death [11]. This is done both on a microscopic and molecular level. Cell biology research extends to both the great diversity of single-celled organisms like bacteria and the many specialized cells in. multicellular organisms like humans. The knowledge of the composition of cells and how cells work is fundamental to all of the biological processes and sciences. Appreciating the similarities and also differences between cell types is particularly important to the fields of cell and molecular biology. These fundamental similarities and differences provide a unifying theme, allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types. Research in cell biology is closely related to breakthroughs in genetics, biochemistry, molecular biology and developmental biology.

Several research findings have linked gender differences with achievement in science. Research evidence has established the fact that there are sex differences in specific abilities of students [10]. It is the contention of many science educators that education generally is skewed in favour of males. Asim [14] observed that the enrolment for science courses in Nigerian universities by males was greater than females. Similarly, Adeyegbe showed the existence of significant effect of gender on achievement. In a study of teaching strategies and determinant of achievement, male achievement was consistently higher than that of females. According to the author, this might be because boys perceive science as a male domain and girls see themselves as cognitively inferior to boys. Oladeji reported significant gender group difference in favour of males in science and mathematics. However, Packard submitted that girls performed better than boys when students were allowed to handle and manipulate 'hands-on activities'.

While Alebiosu [15] found no significant main effect of gender on learning outcomes in chemistry, Okafor [16] reported a significant effect of gender on learning outcomes in chemistry.

In this study, a pre-test, post-test, control group quasi-experimental design. These include instructional strategy at two levels (inquiry method and conventional lecture method) and gender at two levels (male and female). 

The target population for the study included all the Senior Secondary School Class Two Biology students in Akure, South Local Government Area. The choice of SS 2 students was considered most appropriate because they would have been exposed to some basic concepts and skills which would enable them solve problems in Biology.

There are 27 senior secondary schools in the Akure South Local Government Area of Ondo State. Four of these schools are single-sex schools, that is, two schools each are only males and only females respectively. These four schools were excluded from the study. Of the remaining schools, the six schools were randomly selected for the study. The following instruments were used in the study:

•  Students' Biology Achievement Test (SBAT)

• Teachers' Instructional Guide on Conventional Lecture Method (TIGCLM)

• Teachers' Instructional Guide on Inquiry Method (TIGIM)

The researcher designed Students' Biology Achievement Test (SBAT) was based on the topics in the cell concept. This achievement test consists of two sections, A and B. Section A seeks personal information on the students with respect to name of school, gender and age while Section B consists of the achievement test made up of 40 items. Each of the test items is followed by four (4) options (A-D) from which subjects will select the correct alternative. The scoring criteria of the pre-test and post-test will be 1 (one) mark for each question got right. The contents of SBAT used for pre-test were reshuffled for the post-test. This was done to prevent carry over effects. The same achievement test was used for both Experimental Group and Control Group. 

Students' Biology Achievement Test (SBAT) was subjected to validity and reliability mechanism. The face validity of SBAT was done through the advice of qualified and experienced Biology educators to determine its Suitability in terms of language of presentation, clarity of ideas, relevance and applicability to the study. The items were trial tested and subjected to a reliability test - Cronbach Alpha Measure (r= 0.88).

Research Hypothesis 1 

There is no significant difference in the pre-test and post-test mean scores of students exposed to inquiry method when they solve problems in the cell concept.

The analysis of the pre-test and post-test achievement mean scores of students exposed to inquiry method when subjected to t-test is presented in Table 1.

Table 1 shows that t-cal (42.18) is greater than t-tab (1.96) at 0.05 level of significance. The null hypothesis is rejected. Therefore, in this study, there is a significant difference in the pre-test and post-test mean scores of students exposed to inquiry method when they solved problem in the cell concept.

Research Hypothesis 2 

There is no significant difference in the post-test mean scores of students exposed to inquiry method of teaching and those exposed to lecture method when they solve problem in the cell concept.

Table 2 presents the analysis of ANCOVA of the post-test mean scores of students taught with the inquiry and lecture methods.

Table 2 reveals that F-cal (442.29) is greater than F-tab (3.84) at 95% confidence limit. Therefore, the null hypothesis is rejected. This implies that there is significant difference in the post-test mean scores of students exposed to inquiry method of teaching and those exposed to lecture method when they solved problem in the cell concept.

Research Hypothesis 3 

There is no significant difference in the post-test mean scores of male and female students exposed to the same inquiry method of teaching when they solve problem in the cell concept.

The ANCOVA result of the summary of gender and students' achievement when exposed to inquiry method is presented in Table 3.

The null hypothesis is accepted since F-cal (3.78) is less than F-tab (3.84) at 0.05 level of significance (Table 3). Therefore, there is no significant difference in the post-test mean scores of male and female students exposed to the same inquiry method of teaching when they solved problem in cell concept.

The study showed that gender has no significant effect on students’ achievement in Biology. The results in Table 3 reveal no significant difference in the post-test mean scores of male and female students taught with both the inquiry and lecture methods. Although, there was a slight increase in the post-test mean score of male students over female students when exposed to both inquiry and lecture methods, the increase was not enough to cause significant difference when the mean scores were subjected to ANCOVA at 0.05 level of significance. However, it is evident in Table that there was a remarkable influence of the inquiry method in the performances of both male and female students. For instance, the difference between pre-test means score and the post-test mean score was higher in both male and female students taught with inquiry method than in students taught with the lecture method.

Table 1: T-test analysis of pre-test and post-test achievement mean score of students exposed to inquiry method

P<0.05

Table 2: ANCOVA showing the Effects of treatment on students' achievement

P< 0.05

Table 3: ANCOVA summary of gender and students' achievement exposed to inquiry method

P> 0.05

Studies have shown that there is no general agreement on the effect of gender on students' achievement. While some workers reported a significant effect of gender on the achievement of students, others did not. However, the finding of this work agrees with Olagbaju, Alebiosu [15] and Ige whose studies found no significant effect of treatments and gender on students' learning outcomes. This is in contrast to the findings of Inyang & Hannah, Njoku and Ukwungwu that established significant differences of treatments and gender on achievement.

Recommendations

Based on the results and discussion, the following recommendations are made:

• The mode of instruction/teaching of Biology in secondary schools should be reviewed to accommodate a functional student-oriented/activity-based instructional strategy such as the inquiry approach. This will enable Biology students to be problem solvers, thereby leading to improvement in the performance of students in Biology examinations

• The teacher training curriculum at all levels of education should be upgraded to include activity-based instructional strategies

• Secondary school teachers should be. exposed to adequate in-service training through workshops, symposia, conferences and seminars in order to be abreast of modern and effective instructional strategies

Government and other employers of labour should ensure that qualified and competent teachers are engaged for teaching in the secondary schools. A successful use of the inquiry method requires that the teachers who will initiate the approach should be sound, knowledgeable and flexible enough to guide the students into meaningful discussions.

The major conclusions in this study are:

• The inquiry method of teaching the cell concept proved more effective than the conventional lecture method in students' achievement

• Gender or sex difference had no significant effect on students' achievement in the cell concept

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