1 Introduction

Secondary school science education is ever-changing (Davies and McMahon, 2004). The ways in which ideas are presented and adapted to fit the national curriculum and thus the exam boards, makes science an interesting and complex subject to teach. Cellular respiration is one of the more complex topics within biology and can be introduced as early as key stage 2, (between the ages 7-11) within the topic of life processes and with focus being that it is something that organisms do (Harlen et al., 2015 Mcleod, 2018). Cellular respiration is a component of many topics, directly and indirectly, this is seen in the big Ideas in science education by Harlen et al., (2015), where cellular respiration ties into the energy topic through big idea 4 - The total amount of energy in the Universe is always the same but can be transferred from one energy store to another during an event and is a central theme throughout big idea 8 Organisms require a supply of energy and materials for which they often depend on, or compete with, other organisms (Harlen, 2010 Harlen et al., 2015). All life on earth depends on cellular respiration in one form or another, for this reason it is often introduced as part of the topics of Living things and their habitats and Animals, including humans , as their need for food (energy) to survive (National curriculum in England: science programmes of study - GOV.UK, 2015). As children progress through the school years, their ideas will be challenged and/or built upon (Agarkar, 2019). All children come to the classroom with ideas of science, these ideas are gained from their own experiences in the real world. Often pre-constructed ideas and, if unchallenged, can cause misconceptions that may negatively impact future learning. The use of Continuity and Progression throughout the national curriculum are key to assist students learning across the science curriculum. Wierdsma et al., (2016) discusses the idea that therefore, conceptual change is vital in learning and for new or old concepts to be constructed, by allowing preconceived science ideas to adapt or be replaced by new concepts.

Throughout this study I will be looking at how the concepts of Cellular respiration are developed from KS1 through to KS5, in the context continuity and progression across the national curriculum. The National Curriculum sets out to guide educators through the topics that must be taught in the UK. To understand the extent the teaching of the national curriculum translates into taught lessons within the school setting. An analysis of lesson materials, student s books (where possible), the opinions of teaching professionals, alongside literature within the education and science communities on the continuity and progression of the topic of cellular respiration will be discussed. Also it is hoped that a greater understanding into the issues in teaching, assessment for learning, the misconceptions and student s ability to access cellular respiration through the lesson content will be achieved.

2 Continuity and progression in science education

The National Curriculum for England was first introduced in 1989, originally formed to improve education and give guidance on what should be taught (Millar, 2011). Over the past 10 years the detail within the national curriculum has been reduced, to consist of areas of study with basic summaries of potential learning outcomes (Ananthasayanam and Karpagam, 2011). For this reason, the national curriculum is not an operational guide to teaching science. Alongside the national curriculum, schools must consult their chosen exam boards and the approved textbooks for additional guidance when creating teaching resources (Millar, 2011). Continuity and progression are seen throughout the National curriculum, often in the form of repetition of knowledge that progresses in complexity as the student travels up the key stages. The idea of continuity within the context of the national curriculum and indeed science, is that each topic can start off simple, and then be built upon (Toplis, 2015 Mcleod, 2018). For example, to understand photosynthesis a student will first need to know what a plant is and that plants need water to grow. Once the concept of a basic plant is solidly built the student can then start to add the knowledge from other topics, osmosis, evaporation, cell division, etc. At the point of learning about photosynthesis, the topic of animals and plants will have repeated multiple times, with the idea that the foundations of knowledge will be well-formed and the ability to implement new knowledge to the topic (Ananthasayanam and Karpagam, 2011 Agarkar, 2019). The use of continuity throughout the national curriculum has been influenced by several learning theories. The constructionist theory has stayed a prominent influence and is based on the idea that all children construct ideas about the world prior to entering the classroom, as new knowledge is presented, previous ideas are built upon or restructured to support new knowledge (Ananthasayanam and Karpagam, 2011 Tsang and Kwong, 2017 Agarkar, 2019). Although the repetition of ideas may present as tedious, or unnecessary, in the opinion of some academics, (mainly due to the limited time students have in school science classes and the belief that more topics could perhaps be covered within the time frame), the need for repetition and review of previous knowledge, has allowed teachers to see how and where ideas become misconceptions (Galton, 2002 Davies and McMahon, 2004). Therefore, Continuity through repetition in education allows for the continued learning of subjects and topics with the opportunity for students to improve their knowledge and understanding (Toplis, 2015). As a result of continuity throughout the national curriculum and constant review of the curriculum, progression should be inevitable. However, progression is highly dependent upon the way in which subjects are taught and the passion the teacher brings to the class, as well as the ability of the students and the level of differentiation required (Galton, 2002 Ananthasayanam and Karpagam, 2011 Tsang and Kwong, 2017). Therefore, progression is not a guarantee and show be viewed as a process supported by continuity throughout the Key Stages.

The national curriculum does give schools the subjects to be taught but the way this is implemented often fails to support continuity or progression. For example, The division between primary school, key stage 1 and 2, and secondary school key stage 3 to 5 teachers, has meant that the continuity for each topic may not flow smoothly with the movement of students into key stage 3 (Davies and McMahon, 2004). In a report by Galton, (2002) primary school teachers had little or no contact with secondary school teachers, having a profound effect on the level of teaching that took place as the students progressed from primary to secondary school. In the previously mentioned report, it was shown that students starting secondary school were often represented with work they had previously done in key stage 2, this constituted to a loss of interest amongst young people within the science classroom (Galton, 2002). The expectations of science education from the view of students progressing from key stage 2 to key stage 3, should be high. Students have gone from the classroom to a science laboratory and should have the opportunity to do their own experiments. Unfortunately, the lack of continuity between key stage 2 and 3 means the ability to educate at the right level is often missed, allowing for low-level work that under challenges students (Davies and McMahon, 2004).

Although the national curriculum sets the topics of study throughout education, it is the way this guide is translated within the school setting and taught throughout the key stages, that tests the national curriculums strengths and highlights its weaknesses (Mcleod, 2018).

3 Learning theories and their role in Science Education

Within the school setting, there are several learning theories that are in constant use, although some may be used to encourage a behavioural response, rather than to encourage direct learning. Although, some may argue that a disrupted class is not an environment for learning. In the classroom the theories of behaviourism and constructionism are commonplace (Windholz, 1992 Ananthasayanam and Karpagam, 2011 Moore, 2012). Skinner s behaviourism, often used in a behaviour management style, using behaviour charts, praise, and a warning system (often used after positive reinforcement strategies) to discipline students that refuse to follow a teacher s expectations. The theories of learning continued to develop from the 1930s through the works of Bruner, Piaget, Skinner, and Vygotsky to mention a few of many. Although many of their theories have taken criticism and, in some cases, disproved, their work can still be seen throughout education. The national curriculum is a prime example of Piaget s staged development as seen in the transition from primary school to secondary at the age of eleven, as shown below (Moore, 2002, 2012 Piaget, 2008).

1 the sensorimotor period (from birth to about eighteen months)

2 the concrete operational period (from eighteen months to about eleven years).

3 and the formal operational period, from about the age of eleven onwards. (Moore, 2012).

Skinners behaviourism focused on the use of positive reinforcement and the idea of students copying the behaviours of the teacher. Piaget continued to develop the behaviourism theory but focused on the idea that learning happened to the individual and that knowledge was transferred and incorporated by the learner, whereas Vygotsky looked at behaviourism learning as a social and cultural process. The key stages throughout the current curriculum continue to follow in the ideals of the Piaget initialised and Bruner established constructionism and the theory that all students, come to the classroom with preconstructed ideas and that those ideas can be built upon or reconstructed. Bruner, unlike the theorists previous, looked at learning as a Spiralling and argued that ideas were built upon or the learner could replace previous knowledge or go back and relearn in the event that they were presented with a concept that did not fit (Karpagam and Ananthasayanam, 2011 Moore, 2012 Agarkar, 2019).

Science within the school setting from Key Stage 1-5, highlights the importance of understanding how students learn and how vital, it is of these processes to be incorporated into the National Curriculum (Millar, 2011 Harlen et al., 2015). Children, from the day they are born, are learning how to navigate the scientific processes involved in the simplest life processes. For this reason, no two children will enter the classroom with the same level of knowledge. The Key Stages allow for the introduction of new knowledge and knowledge constructed for cultural, social and the child s home environment.

Figure 1. Cognitive elements of cellular respiration. (Wierdsma, Boersma, et al., 2016)

Constructionism in the context of cellular respiration can be seen in Figure 1 from a study by Wierdsma, Boersma, et al., (2016). The ideas are broken down into sections and labelled A-F. Section A showing the need cells have for energy (shown by arrows) and for the process of cellular respiration. All sections are key to a student understanding what the purpose and how respiration takes place. Wierdsma, Boersma, et al., (2016) argue that for a student to understand respiration they must understand sections A, B and C. The results supported their theory and showed that students that could not create a concept map that showed the processes of A, B and C could not define the function of respiration or incorporate the requirement of respiration in different contexts. The inability for students to construct new knowledge without the foundation knowledge of the processes relating to cellular respiration (to allow cells to access energy stored in glucose), or that the context that respiration is used, may not match the knowledge the student currently holds, for example, that bacteria cells require energy to function. Without having the foundations in place constructing a functional concept was no longer possible without relearning or recontextualising the previous knowledge (Wierdsma and Knippels, 2016).

In the context of the national curriculum, the repetition of the base ideas from the start to the end, should enable the construction of more complex ideas and the progression of learning. From my observations and data (from a small sample for students, across Key Stage 3-5 that attend Alexandra Park School) this concept is far more complex and will be discussed further in section 6. Students across the key stages showed a lack of basic knowledge when asked to write down anything they could recall about the topic of cellular respiration.

4 The big ideas and how they shape education

There are currently ten big ideas in science as described in detail by Harlen et al., (2015). Harlen et al., (2015) discuss the use of the big Ideas in science throughout education and sets the tone for what science education should aim to achieve within the classroom and in the continued progression of students learning. Of particular importance, from my position as a student teacher, is the idea that, Science education should enhance learners curiosity, wonder and questioning, building on their natural inclination to seek meaning and understanding of the world , a point that resonated with me when I first read the work of Harlen et al., (2015) and upon rereading continues to inspire my teaching practice. The topic of cellular respiration tends to link into many subjects within biology and chemistry and continues this trend throughout the big ideas. Cellular respirations fits into the topics of energy and the need for resources (glucose and oxygen), this allows cellular respiration to easily inhabit both big idea 2 The total amount of energy in the Universe is always the same but can be transferred from one energy store to another during an event and big idea 8 Organisms require a supply of energy and materials for which they often depend on, or compete with, other organisms (Harlen et al., 2015). Big idea 2 is a complex concept for students to grasp, when then combining it with the equation for cellular respiration and then, looking at the importance of energy throughout all life on Earth. Energy and its movement from one form to another continues to involve itself in the misconceptions associated with the topic of cellular respiration. From my experience working in secondary education over the past two years, the idea that during cellular respiration glucose gives the cell energy seems to be an ongoing theme. Big idea 8, describes the importance of the process of cellular respiration in means of accessing energy to fulfil life processes, the life cycle, and the need for organisms to consume, eat and transfer energy. Big idea 7 Organisms are organised on a cellular basis and have a finite life span also falls into the cellular respiration dependant category (simply anything that requires energy to live) and highlights the idea that once cells are unable to perform their basic functions, cellular respiration ceases and apoptosis follows. From a teaching perspective the big ideas and the national curriculum guidelines help to focus the timing of teaching different topics if not the content of lessons. Unfortunately both curriculum and the big ideas have continued to hold vague and unspecific guidance for the making of teaching content, leading teaching professionals to the idea that the content of their teaching is consistent with the approved textbooks and past exam papers (Millar, 2011).

5 Development of the national curriculum around the topic of `Cellular respiration` through the key stages.

The national curriculum set out to centralise education across the UK. Cellular respiration within the context of the national curriculum for science, is connected to the major life processes of all organisms. Within the school setting cellular respiration as a topic, is introduced formally at key stage 3 in the form of a word equation where oxygen and glucose react to access energy and produce carbon dioxide and water. As students work their way up to key stage 4 there is a progression to the use of chemical equations and the linking of knowledge to the balancing equations topic in chemistry. Cellular respiration as a stand-alone topic, presents a variety of challenges the abstract ideas within cellular respiration the use of the word cellular respiration within the respiratory system or indeed, in the context of breathing, has led to the topic of cellular respiration being prone to misconceptions. The stages of cellular respiration throughout key stage 3 to 5, 3 being extremely basic, with key stage 5 exploring glycolysis, the electron transport chain, and the use of ATP throughout the cell, shows the progression of the topic through the secondary school national curriculum. The national Curriculum builds up in complexity, as shown in the curriculum table (Appendix 1.). Key stage 1 is divided into year 1 and 2 contains the basic knowledge about plants and animals, where they live, and that they need to eat to live. These stages continue to develop gently they build the foundations and allow for more complex ideas to fit into the later learning process.

6 The Teaching of Cellular respiration through the national curriculum guidelines within the school setting.

When identifying how a topic in the national curriculum is implemented in the school setting, it is important to question where the topic is first introduced and how the topic connects throughout the curriculum (Appendix 1.). Cellular respiration, being a complex subject with connections to many other scientific topics, creates challenges for education professionals (Wierdsma and Knippels, 2016 Dam et al., 2019). Alexandra Park School implements the National Curriculum through various schemes of work and department planning. These schemes of work were used to construct a concept map, (see appendix 2.) for comparison with the curriculum table and to identify how the school structures successful learning.

When consulting with teachers at Alexandra Park School it was highlighted, that often the topic of cellular respiration can be misunderstood or lead to misconceptions. Teaching at Alexandra Park School, during a top set, year 10 lesson on cancer, students associated cellular respiration with the mechanical/physical process of breathing and the movement of gasses in and out of the lungs. through questioning the class on this idea and allowing a discussion with the students about the topic of cellular respiration, it became clear that many students believed that cellular respiration was the process of breathing. After discussing the misconception with the year 10 class teacher, Miss O Sullivan, she explained that students were never taught cellular respiration at the same time as the respiratory system to prevent confusion. Regardless of the time between teaching cellular respiration and the respiratory system, students had associated the 2 topics and constructed misconceptions.

After reviewing the conversation with Miss O Sullivan, a simple question sheet was used to question students across the year groups and collected data to see how the topic of cellular respiration was understood by students. The question sheet consisted of a basic question asking students to write down everything they could remember about cellular respiration in 5 minutes. The sheet itself was A5 to limit the amount of space for answering. The time limit of 5 minutes was set to collect data during registration at the beginning of the day without impacting on learning time.

When reviewing the collected data, there were clear misconceptions within the topic of cellular respiration. The results were divided up into different categories. 3 categories were used to show the level of detail cellular respiration was understood, basic understanding (a level of understanding expected at key stage 3), good understanding and detailed understanding (a level of understanding expected at key stage 5). A further 3 categories were used to show, students that could not remember anything about cellular respiration during the task, students that mistook cellular respiration for a different topic i.e., cell division or cell death, and the final category being students that showed common misconceptions (see figure 2.) (Dewi, Zen and Haryani, 2019). The category of misconceptions was further divided into the main 4 misconceptions.

Figure 2. Analysis of students written explanations of cellular respiration during a 5-minute task. Shown as a % of students questioned. Year 11 were not available due to study leave and year 12 were isolating off site due to corona virus. Data from Alexandra Park School.

The data revealed a positive trend in the number of students that had a basic understanding of cellular respiration from year 8 to year 13 (biology) with year 13 biology students presenting higher levels of understanding. The data showed that year 9 students had the highest level of misconceptions at 39%, with year 8 at 18% and year 10 at 12%. This finding when comparing ideas to the structure of the National Curriculum and the theories of learning explanied that, learning is a repetitive process. The idea of respiration is formally introduced as a year 8 topic at Alexandra Park School the learning of respiration needs repetition and to be continuely questioned both by students and by their teacher, in order for learning to be consolidated. The spike in misconceptions may tie in with the fact that in year 8 conciderably more time is spent on the teaching of the organ systems. In perticular the respritray system, the majority of missconseptions had ideas linking to breathing or the movement of gases in and out of the body.

Figure 3. Analysis of student misconceptions of cellular respiration divided into the four apparent misconceptions. Shown as the total number of students with misconceptions. Year 11 were not available due to study leave and year 12 were isolating off site due to corona virus. Data from Alexandra Park School.

Figure 3. shows the four misconceptions and out of the students with misconceptions, the number of students that fit each misconception. Year 9 presents the highest level of misconceptions, both linked to the organ system topics (respiratory system and circulatory system) and are taught in the later part of year 8. This could explain the increase in misconseptions in the beginning of year 9, as chemisty and physics are the topics focused on in the first term (during the time data was collected) and photosynthesis is then taught after christmas break and as a part of that topic a review of respiration with the opertunity to catch misconceptions and build on previous learning. This may also explain why there is a decress in the rate of misconceptions in the years 10 and 13.

The opertunity for catching and reteaching throughout the curriculum for cellular respiration, as shown in the curriculum table (Appendix 1.). The curriculum divides the complexity of respiration into simplier parts adding each part on top of the previous. The aim is that by the time a student has progressed through the key stages, they will have built a strong foundation of knowledge in many subjects and be able to use critical thinking to be able to contribute to society.

7 Discussion

The National Curriculum for science develops the concept of respiration slowly, (Appendix 1.) alongside the ideals of continuity and progression (Ananthasayanam and Karpagam, 2011 Agarkar, 2019). Respiration is not a stand-alone topic and for this reason a simplified curriculum table only showing the parts focused on topics of respiration, cannot reflect the complexity of planning involved in designing the curriculum for science education. For example, between key stage 2 and key stage 3 there is a jump from simple concepts i.e. where animals live and how they survive, to the study of aerobic and anaerobic respiration. It is important to note, that key stage 3 is divided into 3 years 7 to 9, the complexity of cellular respiration is divided across those years and allows for a progression of knowledge but also, an allowance for repetition and relearning of concepts that may have been missed in primary education (Galton, 2002).

When comparing curriculum table content to that of the concept map (Appendix 2.) (designed around Alexandra Park School scheme of work.) It becomes apparent that respiration ties into many topics and is referred to throughout the teaching of those topics. The reason for repetition becomes clear when seen in the classroom setting. In a year 10 class learning about the topic of cancer, students raised the misconception that respiration was breathing and gas exchange. When talking to their teacher, the teacher explained that this was a common issue across all year groups, but through the repetition of questioning students about the topic of respiration the misconception reduced as the students progress through secondary education. Cellular respiration, as shown in my data collected from school students across the secondary key stages, supports the ideas presented by the class teacher, that as students progress their concept of cellular respiration becomes clearer. Interestingly, students that do not study A-level biology, and thus, did not continue to review cellular respiration as a topic or use it within other topics, showed an increase in misconceptions of cellular respiration. In this example, without continuity and repeated practice, misconceptions may not be addressed prior to students leaving education. Whereas students that study A-level biology, had a definite decrease in misconceptions and an in-depth understanding of the topic.

There were limitations to this study, for example, to truly understand the extent of continuity and progression throughout the national curriculum a far larger pool of data would be required. Being that this study has only had access to one school, during a time when education has faced many challenges (due to the COVID-19 pandemic), it would be recommended to continue the study over a far longer period, with many schools surveyed and the use of a more in-depth assessment. With this knowledge there are some changes to implement to better access the depth of understanding students have of any given topic. In future the use of repeat testing and open and closed questioning would allow for understanding to be assessed over time. The number of students sampled would need to be larger and differentiation of assessment to allow for accessibility for all students.

8 Conclusion and Refection

The National Curriculum though not perfect, it does allow for continuity and progression, as well as the flexibility for schools to adapt their teaching of topics to fit the needs of their students. The difficulties observed during my time at Alexandra Park School and the way the students engaged with learning and using the topic of respiration within different contexts gave insight to how students can be supported with their learning and how topics interlink within education. The introduction of Cellular respiration at Key Stage 3 seems appropriate and ties in well with the stages of learning, where children over the age of around eleven years old can process increasingly abstract ideas (Moore, 2012).

Although not what I had expected, Misconceptions allowed for students to reengage with topics and support each other s learning during class questioning. The issue of misconceptions became an opportunity to refine learning within the classroom (although without further assessment it will be difficult to know if the misconceptions remained), the refinement also allowed for students to engage with topics they found difficult without feeling judged. Going forward it will be interesting to find ways to use misconceptions as a tool for learning, with the aim for getting students to support each other s learning and progression.

10 References

Agarkar, S. C. (2019) Influence of Learning Theories on Science Education , Resonance, 24(8), pp. 847 859. doi: 10.1007/s12045-019-0848-7.

Ananthasayanam, R. and Karpagam, S. (2011) Role Of Teachers In Constructivistic Approach , i-manager s Journal on School Educational Technology, 7(1), pp. 14 18. doi: 10.26634/jsch.7.1.1515.

AQA (2017) AS and A-Level Biology AQA Specification , 1(4), p. 14. Available at: http://filestore.aqa.org.uk/resources/biology/specifications/AQA-7401-7402-SP-2015.PDF%0Ahttp://filestore.aqa.org.uk/resources/chemistry/specifications/AQA-7404-7405-SP-2015.PDF.

Dam, M. et al. (2019) Understanding cellular respiration through simulation using lego as a concrete dynamic model , Education Sciences, 9(2). doi: 10.3390/educsci9020072.

Davies, D. and McMahon, K. (2004) A smooth trajectory: Developing continuity and progression between primary and secondary science education through a jointly planned projectiles project , International Journal of Science Education, 26(8), pp. 1009 1021. doi: 10.1080/1468181032000158372.

Dewi, S. P., Zen, D. and Haryani, M. E. (2019) The mapping of science teacher candidate s prior knowledge in cellular respiration topic , JPBI (Jurnal Pendidikan Biologi Indonesia), 5(3), pp. 443 450. doi: 10.22219/jpbi.v5i3.10037.

Galton, M. (2002) Continuity and progression in science teaching at key stages 2 and 3 , Cambridge Journal of Education, 32(2), pp. 249 265. doi: 10.1080/03057640220147586.

Harlen, W. (2010) Principles and big ideas of science education , Association for Science Education, p. 60.

Harlen, W. et al. (2015) Working with Big Ideas of Science Education , Science Education Programme, p. 64. Available at: https://minerva.bathspa.ac.uk/bbcswebdav/pid-932397-dt-content-rid-957672_1/courses/EX-Teach-First-Leadership-Development-Programme/1working-with-big-ideas-of-science-education-print-version-2- %281%29.pdf.

Karpagam, S. and Ananthasayanam, R. (2011) Role Of Teachers In Constructivistic Approach , i-manager s Journal on School Educational Technology, 7(1), pp. 14 18. doi: 10.26634/jsch.7.1.1515.

Mcleod, L. (2018) Developing a framework for the biology curriculum , SSR, 100(370), p. 23. Available at: https://www.rsb.org.uk/images/SSR_September_2018_23-29_McLeod.pdf (Accessed: 23 December 2020).

Millar, R. (2011) Reviewing the National Curriculum for science: Opportunities and challenges , Curriculum Journal. Routledge , pp. 167 185. doi: 10.1080/09585176.2011.574907.

Moore, A. (2002) Teaching and Learning: Pedagogy, Curriculum and Culture, Teaching and Learning: Pedagogy, Curriculum and Culture. doi: 10.4324/9780203487556.

Moore, A. (2012) Teaching and learning: Pedagogy, curriculum and culture, Second edition, Teaching and Learning: Pedagogy, Curriculum and Culture, Second Edition. Taylor and Francis. doi: 10.4324/9780203134061.

National curriculum in England: science programmes of study - GOV.UK (2015). Available at: https://www.gov.uk/government/publications/national-curriculum-in-england-science-programmes-of-study/national-curriculum-in-england-science-programmes-of-study (Accessed: 17 January 2021).

Piaget, J. (2008) Intellectual Evolution from Adolescence to Adulthood , Human Development, 51(1), pp. 40 47. doi: 10.1159/000112531.

Toplis, R. (2015) Learning to Teach Science in the Secondary School, Learning to Teach Science in the Secondary School. doi: 10.4324/9781315731285.

Tsang, K. K. and Kwong, T. L. (2017) Teachers emotions in the context of education reform: labor process theory and social constructionism , British Journal of Sociology of Education, 38(6), pp. 841 855. doi: 10.1080/01425692.2016.1182007.

Wierdsma, M., Boersma, K. T., et al. (2016) Developing the ability to recontextualise cellular respiration: an explorative study in recontextualising biological concepts , International Journal of Science Education, 38(15), pp. 2388 2413. doi: 10.1080/09500693.2016.1246779.

Wierdsma, M., Knippels, M. C., et al. (2016) Recontextualising Cellular Respiration in Upper Secondary Biology Education. Characteristics and Practicability of a Learning and Teaching Strategy , Journal of Biological Education, 50(3), pp. 239 250. doi: 10.1080/00219266.2015.1058842.

Wierdsma, M. and Knippels, M.-C. (2016) Recontextualising Cellular Respiration in Upper Secondary Biology Education. Characteristics and Practicability of a Learning and Teaching Strategy , Journal of Biological Education, 50(3), pp. 239 250. doi: 10.1080/00219266.2015.1058842.

Windholz, G. (1992) Pavlov s conceptualization of learning. , The American journal of psychology, 105(3), pp. 459 469. doi: 10.2307/1423198.