International Journal of Science Education

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International Journal of Science Education

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Identification of misconceptions in novice biology teachers and remedial strategies for improving biology learning Din-yan Yip a a Department of Curriculum & Instruction, The Chinese University of Hong Kong,

To cite this Article Yip, Din-yan(1998) 'Identification of misconceptions in novice biology teachers and remedial strategies

for improving biology learning', International Journal of Science Education, 20: 4, 461 — 477 To link to this Article: DOI: 10.1080/0950069980200406 URL: http://dx.doi.org/10.1080/0950069980200406

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INT. J. Sci. EDUC., 1998, VOL. 20, NO. 4, 461-477

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Identification of misconceptions in novice biology teachers and remedial strategies for improving biology learning

Din-yan Yip, Department of Curriculum & Instruction, The Chinese University of Hong Kong, PRC A new instrument was devised to identify misconceptions in biology and probe into the causes of misunderstanding in a relatively quick way. It revealed that novice biology teachers held a number of conceptual errors which were prevalent among secondary school students. They showed serious misunderstandings in cellular metabolism, the nutritional process, gaseous exchange, the circulatory system, homeostasis, reproduction and variation. The problem has been attributed to inadequate mastery of subject knowledge and imprecise use of terminology. Specific teaching strategies were suggested to prevent the propagation of these misconceptions in students. Teacher education programmes should aim at promoting the awareness of teachers as to children's learning difficulties and developing their professional skills in facilitating children's conceptual development.

Introduction Probing children's understanding of science concepts has been a focus of research in science education since the 1980s (Wandersee and Mintzes 1987, Sanders 1993, Driver et al. 1994, Garnett et al. 1995). These studies have revealed that children possess numerous ideas that are inconsistent with scientific knowledge even after teaching. These children's ideas have been denoted by various terms such as misconceptions (Lawson and Thompson 1988), alternative conceptions (Gilbert and Swift 1985), alternative frameworks (Driver and Easley 1978), preconceptions (Hashweh 1988) and prescientific conceptions (Good 1991). This host of terms now in use, while having created some confusion and barriers for science teachers in understanding research findings and translating them into classroom practice, reflects the underlying idiosyncrasies held by different groups of science educators as regards the nature and causes of children's erroneous conceptions. As each of these terms has its own merits and limitations, science educators at present have not yet reached a consensus on the 'term of choice' for describing children's informal ideas in science. For the sake of simplicity of description, this paper will use the term 'misconception' to denote any ideas held by children that are inconsistent or in conflict with those generally accepted by scientists. Although the identification of misconceptions is an important initial step towards better science teaching and learning, a knowledge of the causes and processes of development of such informal views is essential for designing and constructing effective instructional strategies that aim to prevent or rectify misconceptions. According to the nature and sources of origin, children's 0950-0693/98 $12·00 © 1998 Taylor & Francis Ltd.

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misconceptions in science after formal instruction can be broadly categorized into the following groups:


(1) informal ideas that are formed from everyday experiences which children bring with them to the classroom; (2) incomplete or improper views developed by students during classroom instruction; (3) erroneous concepts propagated by teachers as well as by textbooks. Misconceptions of the first type are generated through children's life experiences and indiscriminate use of everyday language. They are commonly detected in basic biological concepts which are encountered by children in real-life contexts prior to instruction, such as the concept of living, animals and plants, sources of plant food, photosynthesis, respiration, gas exchange and inheritance (Mintzes et al. 1991, Driver et al. 1994). Being established in the cognitive structure before the receipt of formal instruction, these informal preconceptions have been found to be highly resistant to change and to subsequently block the learning of approved science concepts. They can be effectively tackled only by instructional approaches that take children's pre-existing ideas into account. In biology, however, a large number of misconceptions may not have been caused by the personal experiences of the learners (Barrass 1984, Cho et al. 1985, Veiga et al. 1989, Sanders 1993). It is argued that, for certain topics, particularly those that are concerned with more complex or abstract phenomena such as cell division, ultrafiltration in nephrons and the mechanism of circulation, children are less likely to come into immediate and direct contact with them in daily life, and so have little chance to develop their own 'naive' explanations (Lawson 1988). These errors are mainly of the second and third categories, i.e. caused by ineffective learning or poor teaching in the classroom. Misconceptions of the second type are formed as a result of lack of understanding during instruction which may be caused by a variety of factors. Children may form improper or distorted views if the prerequisite knowledge necessary for the construction of a new concept is absent from the cognitive structure. To promote conceptual change, it is essential for the teacher to ascertain that the students have mastered the anchoring concepts before instruction (Ausubel 1968, Garnett et al. 1995). Undue emphasis on the acquisition of factual information, which is a common practice in biology teaching, presents another block to conceptual development. When presented with excessive detail, students tend to resort to a rote learning style which incorporates new concepts as isolated information with little understanding or integration. Another source of misconception comes from teachers who are less competent in subject-matter knowledge. They may propagate incomplete or erroneous views to their students through inaccurate teaching or uncritical use of textbooks (Barrass 1984, Sanders 1993). This type of error is particularly prevalent among students who assume a rote mode of learning with unconditional acceptance of information delivered from the teacher. Misconceptions of the first and second categories have been extensively studied and well documented in life science, but those originating from teachers are relatively unexplored. So far, only a few studies have been reported which investigate the possibility of practising secondary teachers as a source of misconceptions in biology (e.g. Barrass 1984, Sanders 1993, Soyibo 1995). One possible


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reason for this lack of interest is the unfounded assumption that secondary school teachers, being graduates in the appropriate discipline, should possess adequate subject knowledge for teaching the required content of the secondary school curriculum and they should be competent in translating their subject-matter knowledge into curriculum materials for instruction in the classroom. As a result, most teacher education programmes focus mainly on educational principles, instructional methodology and teaching practice; they seldom address the need to promote a deeper understanding of subject-matter knowledge in making a teacher more competent in teaching (Hashweh 1987, Smith and Neale 1989, Tamir 1991). As reflected in the small number of studies available and based on the author's personal observation in classroom teaching of practising teachers, the validity of the above assumption is untenable. In view of the deficiency of research in this aspect of science learning and the great impact of the teacher as a direct agent for passing misconceptions to students, the present study was launched to address the issue of whether practising biology teachers in Hong Kong possess an adequate understanding of subject-matter knowledge to teach the secondary biology curriculum. Method The research instrument A variety of methods have been described in the literature for detecting children's misconceptions in science. Multiple-choice items are commonly used as they can be marked objectively and conveniently. However, they often fail to explore the reasoning processes and sources of conceptual problem of the subjects (Hernandez and Caraballo 1993, Odom 1995). Written tests with open-ended questions, on the other hand, may elicit students' in-depth thinking more effectively, but are difficult to quantify and sometimes too subjective (Simpson and Marek 1988, Themane 1990). Clinical interviews, usually based on questions referring to particular instances or events, can probe into students' mental processes more specifically, but they are time-consuming to administer and require expert skills if they are to be conducted successfully (Piaget 1969, Osborne and Gilbert 1980, Posner and Gertzog 1982, Barman et al. 1995). Construction of concept maps provides a quick means to elicit how children link and organize concepts together, in contrast with the detail that short-answered tests or essays reveal (Novak and Gowin 1984, White and Gunstone 1992). The non-competitive nature of the task is particularly useful in promoting class discussion and co-operative learning. To complement the above methods in acquiring a fuller understanding of children's problems in science learning, a new instrument is used in the present study which can specifically and objectively identify teachers' misconceptions and probe into their causes of misunderstandings in a relatively quick way. This is a written test consisting of 67 questions, each made up of a short statement on a particular biological concept. Teachers are asked to read each statement carefully and point out whether it is correct, partially correct or incorrect, underline parts that they consider to be incorrect and provide justifications for their answers. Misconceptions commonly detected in the biology candidates of the Hong Kong Certificate of Education Examination (HKCEE), which is equivalent to the GCSE level of the UK, are embedded in the questions. Teachers' responses may indicate


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whether they hold similar conceptual errors in biology to their students. If this is the case, it can be implied that some of the misconceptions shown by the biology students would have been propagated by the teachers, who may have taught the subject-matter imprecisely, misleadingly or erroneously. The test items and the answers were reviewed for accuracy in subject content and clarity of expression by two tertiary biology educators who were very experienced in student assessment particularly in running local public examinations. The draft instrument was trialled on two different groups of biology teachers with follow-up discussion. On the basis of the teachers' performance and comments from these pilot studies, appropriate revisions were made on certain items to refine the wording and improve the clarity of expression. The final instrument gives a reliability index of 0.87, as measured by the Cronbach alpha value, indicating a high internal consistency among the constituent items.

Subjects The subjects for this study comprised a group of 26 secondary biology teachers who were participating in a course of initial teacher training, the Postgraduate Diploma in Education. All subjects were university graduates with majors in biological science. Most subjects were novice biology teachers, with teaching experience ranging from 0 to 3 years.

Conduction of the test The teachers were given the test paper at the beginning of the course. They were asked to answer the questions at home and return them to their supervisor at the next lesson which was a week later. The subjects were therefore given enough time to complete the test and were free to consult references in case of doubt. Thus wrong answers given by the subjects will be a clear indication of the existence of some deep-rooted misunderstandings or conceptual problems.

Analysis of results The answer to each item consists of two parts. The first part requires the subject to highlight the part(s) of the statement that is/are incorrect by underlining the relevant words or phrases. The second part is a justification of the subject's choice. An item is considered to be answered correctly only when the incorrect part is highlighted, together with a proper explanation. Thus a wrong response for an item would suggest that the subject holds an erroneous or inaccurate idea of the concept concerned. The elaboration provided by the subject may also reveal her or his thinking processes and the causes of misconception. Of the 67 items making up the test which cover major areas of the Certificatelevel biology syllabus, about half of them (42%) were correctly answered by not more than 50% of the subjects. This paper will focus on an analysis of the performance on some of these poorly answered items which reveal significant conceptual problems among the present group of practising teachers. These items are concerned with concepts in the following areas: cellular metabolism, the nutritional


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process, gaseous exchange, the circulatory system, homeostasis, reproduction and variation. In light of the nature and possible causes of the conceptual problems, remedial strategies are suggested for improving classroom instruction and preventing the propagation of the misconceptions to the students.


Results and discussion Cellular metabolism The optimum temperature for enzyme activity: The first item states that 'The optimum temperature for enzyme activity is 37° because this is our body temperature'. Although this item is concerned with a simple and basic biological principle on enzyme activity, it was correctly answered by only half the subjects. Many subjects held the erroneous view that all human enzymes worked optimally at the body temperature, i.e. 37°C. They contended that the human body temperature was always maintained at 37°C by a sophisticated homeostatic mechanism, and deviation of a few degrees would be fatal, an idea well established even in early childhood. Based on this alternative conception, it was implied that human enzymes worked best at the body temperature and a drop or rise in body temperature would lead to a loss of enzyme activity and subsequently a breakdown of body functions. This misconception is reinforced in textbooks and practical manuals. In order to provide a simplified picture that is comprehensible to students, many textbooks use inaccurate expressions that may lead to misunderstanding, such as 'enzymes work efficiently or best at the body temperature' (Wynsberghe et al. 1995). Some laboratory manuals recommend incubating enzyme-substrate mixtures at 37°C in order to obtain a good result, suggesting that this temperature is optimal for enzyme action (Sparks and Soper 1988). To avoid propagating this idea to students, the teacher should point out explicitly to the class that the optimum temperature of most enzymes lies between 40 and 45°C. But this may not be effective enough to rectify an idea that has been well established prior to instruction. The following strategy may help to challenge students to consider the inadequacy of their preconception and facilitate conceptual changes: • Ask the class to consider the following situation: A person suffering a fever may have a body temperature of 40°C or even higher. Will the person have a reduced metabolic rate or suffer metabolic breakdown? • Carry out investigations to find out the optimum temperature of some mammalian enzymes, such as catalase from pig's liver, trypsin from ox or amylase from human saliva. This will bring out the point that the optimal temperatures of mammalian enzymes are variable and usually higher than 37°C. It will be quite surprising or even shocking for the students to find out that the human salivary amylase works best at 60—70°C and papain, a nonmammalian enzyme found in meat tenderizer, can still carry out its proteolytic action efficiently at 70-80°C (Yip 1994)! Such unexpected results provide a cognitive conflict that challenges the students to review their original idea and make appropriate adjustments.

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• The following question may help to consolidate the revised view on enzyme action: If most human enzymes work best at 40-45°C, why is it that a body temperature above 40°C will be dangerous to the body, especially the nervous system? The mechanism of photosynthesis: This question states that 'Photosynthesis is made up of a light reaction and a dark reaction'. This statement was considered to be correct by majority of the subjects (88%) and, as based on the author's observation in the classroom, similar statements are frequently delivered by teachers during lessons. The general acceptance and use of such an imprecise statement, however, may not suggest the existence of any conceptual errors as the teachers, being specialized in biological science, should know the biochemical pathways involved. It is just an attempt by the teacher to provide a simple overall picture of the mechanism of photosynthesis. The problem with this over-simplified statement is that it is misleading to the students, who do not have a knowledge of the historical account of Warburg's flashlight experiment or the empirical evidence leading to the establishment of the Calvin cycle. Using the terms 'light' and 'dark' reactions without suitable elaboration by teachers and textbooks has led to the development of a variety of conceptual errors in students. For example, many students have developed the erroneous view that photosynthesis is made up of two reactions and that the dark reaction takes place only in the dark or at night. Some even equate the dark reaction with the process of respiration (Amir and Tamir 1993). To avoid confusion and misunderstanding, the terms 'light' and 'dark' reactions should be replaced by 'light-dependent' and 'light-independent' stages. It is also important to stress to students that each stage is made up of a series of enzyme-catalysed reactions and that the second stage is dependent on the products of the first stage. In view of the highly abstract nature of this topic, conceptual development can be facilitated by the use of flow diagrams or concept maps that highlight the key points of the interaction and relationship between the two stages. Meaningful learning can also be enhanced by ensuring that the students have acquired the prerequisite concepts before receiving instruction on the mechanism of photosynthesis, such as the raw materials and conditions for photosynthesis, the empirical evidence involved and the adaptive features of the leaf. The nutritional process Energy supply from, the diet: This question states that 'Our daily energy supply comes mainly from carbohydrates and fats'. Most subjects (58%) erroneously considered that proteins in the diet were only important as an organic material for forming body cells and structures, as normally described in textbooks, but could not be used as an energy source. They argued that excess proteins or amino acids from the diet could not be stored in the body and they would be decomposed and excreted as urea. From everyday experience and the A-level and university biology courses, the subjects should have learned that protein is a main component of our daily diet and any protein in excess of our body's need for forming body structures will be broken down to form carbohydrate or lipid, which can be stored up or oxidized to provide energy for body metabolism. The subjects should also know



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that protein has an energy value similar to that of carbohydrate. However, many subjects failed to make meaningful connections between these points, but asserted that protein was not important as an energy source. In order to justify their answer, a few even suggested that the energy used in deamination of amino acids would be so great that the net amount of energy subsequently gained from oxidation of the derived Q-keto carboxylic acids would be insignificant, showing an inadequate knowledge of the biochemical principles involved. The above problems seem to be related to the fact that knowledge of protein as an 'energy-rich' food substance and as a body-building material are learned in different contexts of the school curriculum. There is little attempt to establish a functional relationship between these concepts and so students as well as teachers tend to memorize them as isolated pieces of information. T o prevent compartmentalization of concepts, students can be asked to use a list of concept labels to construct a concept map that links the protein in the diet with the fates of assimilated protein in the body (figure 1). Such an activity can help students to evaluate the relationships between separate processes of the body and construct an integrated picture of protein metabolism.

protein in diet I digestion] amino acids in small intestine [ absorption | amino acids in blood assimilation

amino acids in cells

enzymes and ^^_ other cellular ^ structures

. ^ ^ ^ organic part + ammonium

carbohydrates

or lipids V

V

V

V ^ | excretion through kidney

for oxidation or storage Figure 1.

Metabolism of protein in the body

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The concept map can also be modified to provide activities that help to assess and consolidate students' understanding of relevant concepts. For instance, a completion exercise can be devised by leaving out the labels of certain key concepts or steps, or students can be asked to assign the names of different stages to their appropriate places on the concept map. Absorption of fat: This question is made up of the statement that 'Fatty acids and glycerol, the product of digestion of fat, are absorbed into the lacteals of the villi'. The majority of the subjects (73%) thought that fatty acids and glycerol, formed as a result of fat digestion, were absorbed directly into the lacteals of the villi. They did not know that fatty acids and glycerol recombine to form fat in the epithelial cells of the small intestine, and the fat, in the form of chylomicrons, is passed to the lymph of the lacteals, giving the lymph a milky appearance. As the same misconception is also common among secondary school students (HKEA 1993), it is highly probable that the subjects might have got this idea in school from their teachers having presented a simplified but misleading version of the mechanism of fat absorption. To avoid propagating this wrong idea to schoolchildren, it is necessary to strengthen teachers' understanding of this topic in their undergraduate biology courses or postgraduate teacher education programmes. A good grasp of the mechanism involved will enable the teachers to produce a simplified and yet accurate version of the process for presentation to their students. A teaching strategy employing an active reading activity (Sheffield City Polytechnic 1992) is suggested below that may help students to construct the concepts involved: Ask the class to read a prescribed text on fat digestion and then answer the following questions: • What are the products of digestion of fat in the small intestine? What agents (enzyme and other substances) are involved in this process? • What is the normal appearance of the lymph in the lacteals of the small intestine? Why does it become milky after a fatty meal? • How would you compare this change with the emulsion test for fat? • How are the products of fat digestion carried in the lymph after absorption? Students have learned that the lymph is a colourless fluid and the emulsion test is a food test for detecting fat or oil, but they can seldom relate these two points to account for the appearance of the lacteal after a fatty meal. By bridging the concepts learned in different contexts, the foregoing exercise will challenge the students to evaluate their existing knowledge critically and help them to form a more meaningful synthesis of apparently isolated events. Breakdown of excess proteins: This question consists of the statement that 'In the liver, excess proteins are deaminated to form urea'. All the subjects considered this statement to be correct, a misconception that is also very common among Certificate-level students (HKEA 1996). In the human body, excess amino acids are normally deaminated to form ammonia and a-keto carboxylic acids; the



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ammonia then combines with carbon dioxide to form urea through the ornithine cycle while the carboxylic acids are metabolized as carbohydrates or lipids. The fallacy of the teachers therefore lies in the indiscriminate use of terminology. By using the term 'deamination' in the wrong context, the teacher will not only encourage students to learn by rote, but will also foster the development of an erroneous view on the process of urea formation in students. Misconceptions of this type, once developed, are difficult to correct and will adversely affect subsequent learning. To guard against the propagation of this conceptual error and rote memory of terminology, the 1996 HKCEE Biology Subject Report recommends teachers to focus on the functional significance of the breakdown of excess amino acids in the body and avoid using the term 'deamination' indiscriminately at the Certificate level (HKEA 1996).

Gaseous exchange This item refers to the statement that 'During exhalation, the lungs are compressed and air is expelled from the air sacs'. T h e majority of the subjects (92%) failed to point out the fallacy of the statement that air was expelled from the air sacs during exhalation. This simplified version of ventilation appears in many textbooks and most teachers consider this as acceptable. Such a description, however, will create a conceptual conflict in students as it is incompatible with the idea of residual air. As the lungs cannot be compressed completely during exhalation, most of the air in the air sacs cannot be expelled and this forms the residual air. To resolve this conflict, the teacher should guide the students to see that although the residual air in the air sacs cannot be expelled directly, there is a continual diffusion of oxygen from the tidal air to the residual air and of carbon dioxide in the reverse direction. To make the learning context more meaningful, it is necessary to point out to students that because of the existence of residual air, which prevents direct gaseous exchange taking place between the blood and tidal air, the process of gaseous exchange is not very efficient and the exhaled air still contains as much as 16% of oxygen and only 4% carbon dioxide. This clarification is useful in dispelling a prevalent misconception of secondary students that the exhaled air is composed mainly of carbon dioxide (HKEA 1996: 195). This can be followed by a class discussion of how the knowledge can be applied to the principle of mouth-to-mouth resuscitation. The relatively high concentration of residual oxygen in the exhaled air can also be the starting point for a discussion on the efficiency of the mammalian ventilation mechanism and how its design may be further improved so as to support a metabolically more active life form.

The circulatory system Blood flow at the capillaries: No subject could identify the fallacy embedded in the following statement: 'In the mammalian circulatory system, the blood flow rate is lowest at the capillaries because the very narrow capillaries offer great resistance to blood flow.' Most teachers considered the first part of the statement as correct (i.e. the blood flow rate is lowest at the capillaries) but gave various wrong justifications for the low flow rate. Some asserted that the reason given in the question was


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basically sound while some suggested that the rapid drop in blood pressure along the capillaries, as caused by high resistance of the narrow vessels, would be a more precise explanation. A few teachers, on the other hand, stated that blood would flow fastest in the capillaries because they were very narrow. The variety of erroneous ideas held by the teachers can be attributed to a poor understanding of the physical relationships between flow rate, blood pressure and vessel diameter (Yip 1998). In a closed circulation, the volume of blood flowing through any cross-section of the circulatory system per unit time is constant, so that the flow rate of blood at a particular point of the system is inversely proportional to its total cross-sectional area. It follows that the very low rate of blood flow in a capillary network is a consequence of its large total cross-sectional area. On the other hand, the very narrow diameter of the capillaries results in a high resistance to blood flow, and this leads to a significant drop in blood pressure along the capillaries. The details of these physical principles, while too demanding for students to comprehend, should be mastered by teachers so that they are able to present a simplified and yet precise version of the relationships without losing accuracy. The basic point to be stressed to students is that the rate of blood flow at a particular point of the circulatory system is not determined by the blood pressure, but by the relative total cross-sectional area at that point. On the other hand, the high resistance of the narrow and numerous capillaries will result in a rapid drop in blood pressure along the capillaries as more energy is required to move the blood along them.

Exchange of substances at the capillary network: When considering the statement 'The formation and absorption of tissue fluid in the capillary network is essential for the exchange of nutrients and wastes between the blood and body cells', most subjects (92%) wrongly associated the exchange of materials between the blood and body cells with the formation and return of tissue fluid. They asserted that at the arterial end of the capillary network, as some plasma was passed out of the capillaries to form tissue fluid, oxygen and nutrients were carried out of the blood by mass flow. In a similar way, as the tissue fluid was returned to the capillaries at the venous end, metabolic wastes were carried along. In most H K textbooks, the way in which tissue fluid is formed and withdrawn in the capillary network is well elaborated, but the mechanism of exchange of substances between the blood and tissue cells is seldom described. Based on such incomplete information, students as well as teachers tend to extrapolate, though wrongly, that the movement of tissue fluid is the main channel for exchanging substances in the capillary network. To make up for this deficiency in textbooks, teachers should secure a deeper understanding of the mechanisms of the two processes by consulting reference books on human physiology, and be aware of the fact that the movement of tissue fluid plays only a minor role in the exchange of materials in the capillary network (Vander et al. 1994, Yip 1998). The exchange of nutrients and wastes in the capillary network mainly takes place by diffusion across the capillary wall. By guiding students to consider how the process of diffusion will be facilitated by the low blood flow rate, the very thin vessel wall and the presence of numerous narrow branches that make up the capillary network, they can develop a meaningful understanding of the adaptive features of the


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capillary network in relation to its role in exchanging materials between the blood and body cells.


Homeostasis Water absorption in glomerular filtrate: In response to the statement that 'Most water of the glomerular filtrate is reabsorbed in the loop of Henle and the collecting duct', the subjects demonstrated a variety of conceptual errors such as most water is reabsorbed in the loop of Henle, in the distal tubule or in the collecting duct. Many subjects (62%) were ignorant of the fact that over 80% of the water in the glomerular filtrate is reabsorbed in the proximal convoluted tubule, accompanying the reabsorption of glucose, amino acids and mineral salts, while the amount of water absorbed in the distal convoluted tubule and the collecting duct varies according to the hydration state of the body, thus serving the role of osmoregulation. The poor performance on this item suggests that many subjects might not have learned this in their undergraduate courses and their erroneous ideas probably originated from instruction received in school. This is evidenced by the performance on a multiple-choice item in the 1994 HKCEE Biology paper in which less than one-third of the candidates were able to identify correctly that most water in the glomerular filtrate was reabsorbed in the proximal convoluted tubule, while many of them suggested the loop of Henle or the collecting duct as the main site of water reabsorption (HKEA 1994). The development of this conceptual error may be attributed to the way in which the mechanism of urine formation is normally taught in the classroom. Many teachers, by faithfully following textbook materials, usually start the topic by introducing a formidable list of terms such as nephron, Bowman's capsule, glomerulus, proximal and distal convoluted tubules, loop of Henle and collecting duct. Many of these difficult terms are not essential for comprehending the mechanism involved, but, by overloading the mental capacity, present a block to concept formation. Consequently, lack of understanding may compel the students to assume a rote learning mode that leads to the development of various misconceptions on the roles of different parts of the kidney tubule. To guard against rote learning, the first step is to reduce the extent of memory work required for this topic. For instance, terms like 'the loop of Henle' should not be introduced as the mechanism of the counter-current principle is not required at this level of study. Simpler terms like 'kidney tubule' and 'first coiled tubule' can be used without sacrificing accuracy. To facilitate concept construction, students can be asked to consider what changes will occur to the water potential of the glomerular filtrate in the proximal tubule as glucose and other useful substances are reabsorbed and what will be the effect of the increased water potential. By using appropriate probing questions, students can be guided to relate the process of active uptake of solutes to the principle of osmosis and build up the concept that a considerable amount of water is reabsorbed in the proximal tubule, which is more or less independent of the state of hydration of the body. Further reabsorption of water at the collecting duct from the remaining fluid then provides the means for regulating the amount of water to be excreted according to the needs of the body. The same principle can also be applied to establish the point that most of the water in the gut is absorbed in the small intestine, accompanying the absorp-

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tion of digested food substances, rather than in the colon (Marieb 1992, Vander et al. 1994). Regulation of body temperature: This item states that 'When the body temperature rises, vasodilation occurs in the capillaries of the skin so that more heat is lost from the skin surface'. Many subjects (85%) wrongly considered that skin capillaries dilate to promote heat loss, a point that is also elaborated in some local textbooks. This reflects a poor understanding of the mechanism of body temperature regulation and indiscriminate acceptance of textbook information. This misconception is also widespread among Certificate-level students (HKEA 1995: 182). Actually, vasodilation occurs in the arterioles which lie in the deeper part of the dermis in response to a rise in body temperature, leading to a more rapid and abundant supply of blood to the superficial capillaries. In most biology textbooks, the diagram for the skin section does not reveal the arterioles which are located in the dermis and supply blood to the superficial capillary plexus. This missing link thus prevents students visualizing how blood supply to the skin capillaries is controlled during temperature regulation and leads to various misunderstandings. To clarify the idea of vasodilation, students should be prompted to review the structural differences between the capillary and arteriole. The contraction and relaxation of the smooth muscle layer in the vessel wall allows an arteriole to constrict and dilate, enabling it to regulate the amount of blood supplying a certain organ. A capillary, on the other hand, cannot perform this role as it is only made up of a squamous epithelium. To avoid memory overload, terms like 'vasoconstriction' and 'vasodilation' should be replaced by simpler words such as dilation and constriction which are more meaningful to the students.

Water relationship in plants: Only a small number of subjects (27%) could point out the fallacy in the statement that 'Stomata are usually absent in the epidermis of submerged leaves otherwise water will enter into the intercellular spaces and the mesophyll cells would become suffocated'. Many subjects thought that if stomata were present on the surface of submerged leaves, water would pass through them and fill up the intercellular space in the mesophyll, thus effectively blocking the process of gaseous exchange for photosynthesis. Some suggested that stomata were important for the process of transpiration to occur; as no evaporation took place in an aquatic environment, there was no need for the stomata. The same misconceptions have been identified in the 1996 Certificate examination in which many candidates attributed the absence of stomata in submerged leaves to the lack of transpiration (13%) or to the role of preventing entry of water into the air spaces of the leaves (38%). These responses reflect that a misunderstanding of the basic role of stomata in land plants is prevalent among both teachers and students. Many of them fail to realize that since there is no problem of evaporation for aquatic plants, the epidermis of submerged leaves is usually made up of thin-walled cells and is not covered with a cuticle. It is therefore freely permeable to dissolved gases in water, and there is no need to have stomata for gaseous exchange as in aerial leaves. Consequently, stomata become degenerated or absent in many submerged leaves. The following prompting questions can help students to construct a proper understanding of the role of stomata:


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By guiding students to relate the absence of a waxy cuticle to a freely permeable surface, they are able to build up the idea that stomata are no longer required


Refer to a photomicrograph showing a vertical section of a submerged leaf and an aerial leaf. • Compare the surface of the two leaves. Which one is covered with a cuticle and has thick-walled cells? How is this feature related to the environment of the leaf? • Which surface would be more permeable to gaseous substances? (Which surface would allow gaseous substances to pass through more freely?) • How will carbon dioxide in the surrounding medium enter the mesophyll cells in (a) the submerged leaf and (b) the aerial leaf? Why are stomata absent in the submerged leaf but present in the aerial leaf? in a submerged leaf for gaseous exchange. Establishing a scientific explanation for the degeneration of stomata in a submerged leaf will challenge the students to reconsider their preconception about the role of the stomata in an aerial leaf as channels for transpiration. By contrasting with the aquatic environment, the students will be able to appreciate the importance of having an impermeable waxy cuticle over the thick-walled epidermis for an aerial leaf to reduce the danger of desiccation. This will subsequently lead to the construction of a proper view of the role of stomata as a channel for gaseous exchange and the accompanying water loss as a necessary evil of such a design.

Reproduction and variation

The nature of the pollen grains: This question states that 'The pollen grains, like the sperms in animals, are the male gametes of flowering plants'. About half of the subjects wrongly considered that the pollen grains were equivalent to the male gametes. This misconception is also common among Certificate-level students (HKEA 1996). It is therefore highly probable that the subjects had acquired this wrong idea in the classroom as secondary school students and that the error had not been adequately dealt with in their undergraduate courses. Because of the very small size of pollen grains, young children may have formed the erroneous view that they are the male gametes of the flowering plants at an early age. Simply teaching the scientific view may not be effective in rectifying this preconception. Learning activities should be designed to expose and challenge the students' preconception, thus alerting them to the inadequacy of their pre-existing idea. A simple activity that will help students to descriminate pollen grains from sperms is to observe the germination of pollen grains in a sucrose solution. The scientific view should then be presented in a meaningful context, e.g. observing the structure of a common fruit like tomato and tracing its process of development from the flower. Models and wall charts are particularly useful as they can help students to visualize the complex process of pollination and fertilization in a concrete way.


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Adaptation to the environment: This question refers to the statement 'Genetic variation among the offspring enables them to become better adapted to the environment'. A common misconception among the subjects is that genetic variation makes the individuals better adapted to the environment. This idea, reminiscent of Lamarck's theory of inheritance of acquired character, may have been formed by children from everyday experience before they receive formal instruction on this topic. The relationship between genetic variation and evolution is a difficult concept for secondary school students. As the context of evolution is an issue sensitive to certain religious beliefs, many local biology teachers, intentionally or unintentionally, tend to give only a superficial treatment of this topic. Furthermore, teachers generally do not have a good grasp of the principles of natural selection as this topic has only been included in the local secondary biology curriculum in recent years. It is therefore highly probable that the informal preconception about the effects of genetic variation on a population is not adequately dealt with in classroom teaching or may even be reinforced by the teachers themselves. To promote a proper understanding of the process and significance of natural selection, greater emphasis should be put on this topic in the secondary biology curriculum by applying it to interpret other biological principles such as the adaptive features of certain physiological processes and ecological relationships. Another approach is to use evolution as a central theme for organizing and structuring the subject-matter of the biology curriculum (BSCS 1963, Butts and Prescott 1990).

Conclusions The present study is based on a new instrument that can probe into subjects' conceptual understanding and identify their misconceptions specifically in a relatively quick way. Analysis of subjects' responses reveals that practising biology teachers show confusion or misunderstanding in respect of a number of basic biological concepts that are required in the Certificate-level biology curriculum. Conceptual problems are particularly prevalent in areas such as cellular metabolism, the nutritional process, gaseous exchange, the circulatory system, homeostasis, reproduction and variation. This is a major cause of concern for biology education as many of these misconceptions are also detected in Certificate-level students and it is highly probable that teachers may have served as a direct agent for propagating and reinforcing the incorrect views to their students. The incompetent subject knowledge of teachers suggests that the undergraduate courses taken by potential biology teachers may not be able to equip them with a strong foundation in the discipline for teaching the secondary biology curriculum. This problem can be attributed to the large variety of optional courses open for selection in undergraduate studies. While this type of course design may be able to cater for the diverse interests and needs of university students, it would also mean that some may graduate without a sound background in all major areas of biological science, which is a prerequisite for a teacher to teach biology competently at the Certificate or Advanced levels. The problem is even more disturbing when it is found that even experienced teachers demonstrate similar conceptual problems (Barrass 1984, Hashweh 1987, Tamir 1991, Sanders 1993).



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However, some of the mistakes committed by the teachers in this study are not necessarily caused by misconceptions, but may be due to imprecise or careless use of terminology, such as in the contexts of deamination, light and dark reactions in photosynthesis, removal of residual air during gaseous exchange and the nature of pollen grains. In attempting to present a complex idea in a simplified way that is appropriate to the level of the students, teachers and textbooks often use imprecise terms or statements that are open to different interpretations. Without an in-depth treatment of the topics involved, students are often misled by such terms or statements and develop conceptual errors. To avoid this, teachers should be educated to use textbooks more critically and selectively, and be alert to the inaccurate information described in textbooks. To be effective in rectifying teachers' misconceptions and preventing these being propagated to students, teacher education programmes should aim at equipping biology teachers with the following knowledge and skills: (1) What science educators have found out about students' misconceptions in science: This knowledge helps the teacher to develop an awareness and understanding of the nature and sources of students' misconceptions, which is a first step in designing suitable instructional strategies. (2) Methods for diagnosing misconceptions held by students before and after instruction: This information allows the teacher to monitor students' learning problems, which will provide continuous feedback on the effectiveness of the teaching strategies used. (3) Designing instructional strategies that tackle students' preconceptions and misconceptions: This involves planning and structuring curriculum materials and learning activities using the constructivist approach that aims at promoting conceptual changes and development, such as the use of examples and analogies, cognitive conflicts, concept maps, demonstrations and student activities (Hashweh 1996). (4) Reviewing selected areas of subject-matter in which teachers have conceptual problems: In view of the fact that many practising teachers demonstrate the same conceptual errors as the Certificate-level students, they are likely to be a direct source of students' misconceptions. Many of the teachers' misconceptions may have been developed in schools and remained unmodified throughout later studies. As mastery of subject-matter knowledge is a prerequisite for a competent and effective teacher, teacher training courses should provide learning experiences for teachers to refresh and consolidate their understanding on certain difficult concepts of the school curriculum. The type of exercise used in this study has been found to be particularly useful in motivating teachers to expose their conceptual problems, committing them to discuss the inadequacy of their informal ideas, and challenging them to construct a more in-depth understanding of related subject-matter. In the last few years, the Faculties of Education of two major universities in Hong Kong (the University of Hong Kong and the Chinese University of Hong Kong) have incorporated the above elements into their pre-service and in-service programmes for potential and practising biology teachers. It is hoped that such provisions can promote the awareness of teachers of children's learning difficulties

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and develop their professional skills in facilitating children's conceptual development in the study of biology.


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