Keywords: micro-organisms, mental model, expressed model

Models of micro-organisms: children's knowledge and

understanding of micro-organisms from 7 to 14 years-old.

 Gilbert & Boulter (1998:92)define models as representations of 'ideas, objects, events, systems or processes'. Mental models are an individual's images, personal ideas, or internal representations about a particular phenomenon, set of ideas, or concepts [START_REF] Gilbert | Models and explanations, part 1: horses for courses[END_REF]. As such, they provide an indication of the ideas held by individuals at a particular point in time (Duit &Glyn, 1996;[START_REF] Greca | Mental models, conceptual models, and modelling[END_REF] although they are not thought of as static entities. [START_REF] Johnson-Laird | Mental Models[END_REF] considers that mental models are dynamic representations; that they are never complete and continue to enlarge and improve as new information is added. As [START_REF] Ausubel | Educational Psychology: a cognitive view[END_REF] states, meaningful learning requires the structuring (and restructuring) of specific concepts that relate to existing concepts in the learner's cognitive structure, suggesting a dynamic to-ing and fro-ing of ideas. A mental model can, therefore, provide an indication of what an individual understands about a concept at a particular point in time and includes their knowledge of, as well as his or her beliefs about, the concept. Therefore the study of mental models has increased in science education as a way of helping to understand the process of learning and, in particular, the representational nature of knowledge [START_REF] Greca | Mental models, conceptual models, and modelling[END_REF]. Attempting to define the mental models children hold, at different ages, about micro-organisms, will begin to identify the nature of children's understanding, as well as helping to develop a view of the progression of ideas across the three age groups presented here. Eliciting their expressed models will provide the means to do so.

An expressed model about a concept, phenomenon or event is an external representation of a mental model and can be accessed through a variety of methods including drawing, writing or talking [START_REF] Buckley | Investigating the role of representations and expressed models in building mental models[END_REF]. Analsying an expressed model can provide an insight into an individual's conceptualisation of an event, phenomenon, or concept and thus elicit information about the knowledge and understanding an individual has of the concept under scrutiny. The relationship between an expressed model, a mental model and the individual's perceptions of the phenomenon being explored is iterative. An expressed model provides insights into a person's mental model but as experience through direct or indirect learning occurs, perceptions of that phenomenon will alter, thereby changing the mental model and thus altering the expressed model. Therefore it is relevant to compare the three age groups as a way of exploring how models of micro-organisms change with time and experience. The expressed models of micro-organisms that children of 7, 11 and 14 years hold is explored in terms of:

• classification

• morphology

• size and scale

• living and non-living

• disease and health

• ecology ( location and decay)

• technological applications

The expressed models obtained from the data were scrutinised in an attempt to develop a set of mental models that offer some coherence to the range and variety of individual ideas elicited in order to inform pedagogy and curriculum developers.

The research question is:

1. What mental models do children at 7, 11 and 14 years hold about microorganisms? A total of 458 children, 176 aged 7 years, 174 aged 11 years and 108 aged 14 years were involved in the research, although a small number of children in each age group did not complete all tasks due to absence on the day of some of the data collection. All children attend Local Authority (LA) maintained schools in the South of England and the schools have catchment areas that enabled the sample to be broadly representative of the whole population.

The participants

They included two infant schools, two junior schools, one primary school and one secondary school. The research took place towards the end of the summer term when the children were all at the end of a specific stage in their formal schooling and had been taught the relevant science curriculum (Department for Education and Employment [DfEE], 1999). In England, it has been a statutory requirement since the introduction of The National Curriculum that children between 7+ and 14 years-old are taught about micro-organisms. There is no requirement for children younger than 7 years and therefore these children in this study are unlikely to have any formal education about micro-organisms. The 11 year-olds have been taught that micro-organisms are living organisms, often too small to be seen, and that they may be beneficial, for example in breaking down waste or assisting in the production of bread, or harmful, for example in causing disease or making food go mouldy. The curriculum for 14 year-olds builds on this knowledge to some extent although it deals specifically with micro-organisms in relation to human health. This age group will have been taught how the growth and reproduction of bacteria and the replication of viruses can affect health, and how the body's natural defences may be enhanced by immunisation and medicines. As far as the authors know there was no were no recent media stories or campaigns about micro-organisms that were likely to have influenced children's ideas at the time of the field work. The study A variety of methods and data collection techniques were used to elicit children's ideas enabling them to be probed in depth and from different perspectives; allowing not only an overview of knowledge and understanding, but capturing any qualitative and quantitative changes that occur at each age group. In this way it was anticipated that the data obtained would allow children's expressed models of micro-organisms at the three different ages to emerge providing an indication of progression in conceptual understanding, as well as the development of generalised mental models. The following methods of data collection were employed • Drawings [START_REF] Reiss | An international study of young people's drawings of what is inside themselves[END_REF] suggest that drawings can represent a child's expressed model of a particular phenomenon which is placed in the public domain. Whilst these models relate to, but do not equate with, their mental models (the private and personal cognitive representations), they can provide a useful guide to children's ideas by gathering a rich mass of data with relative ease, as well as supplement other research methods [START_REF] Hayes | Drawing during science activity in the primary school[END_REF][START_REF] Reiss | An international study of young people's drawings of what is inside themselves[END_REF]. The children were asked to draw a picture of a microorganism and then write down anything about their drawing that they wanted to [START_REF] Williams | A picture of health: What do you do that makes you healthy and keeps you healthy? London[END_REF]. This instruction may have resulted in children drawing a single item and therefore skewing the data, however this did not universally occur. Drawings and annotations were expected to elicit data across all conceptual areas but analysis revealed that this was not the case. Qualitative analysis was undertaken by attributing characteristics of the drawings and annotations to particular categories and then coding within the categories that emerged from examining and re-examining the drawings (Table 1

• Brainstorming

After children had completed their drawings they were asked to turn their paper over and write anything that they knew about micro-organisms (children who had difficulty in writing were provided with a scribe). This technique provided children with the opportunity to undertake a free thinking exercise and allowed them to present their ideas in a different format and was expected to elicit ideas across all conceptual areas. The brainstorms were analysed in the same manner as the drawings, by examining and re-examining the data (Table 1).

• Concept mapping

Concept maps are a visual representation of the relationship between different concepts. [START_REF] Kinchin | Concept mapping in biology[END_REF] considers that concept maps are a useful way of collecting information, and because they are flexible, they can be adapted for use by almost any group of learners. The challenge within the context of this research was to design a tool that would be accessible to children in each age group. A new research tool, concept mapping using a photograph association technique (CoMPAT) was developed to overcome these issues (Author). The children were asked to complete concept maps using labeled photographs that illustrate a range of microbial activities which the oldest children in the sample should have some knowledge of as a result of school teaching. The key areas of microbial activity and the photographs that represent the concepts are:

• disease and health (sick child) • application of micro-organisms in traditional food technology (bread, beer, yogurt); medication (vaccination and antibiotics) and environmental applications (compost heap and sewage works).

The photograph association concept maps produced by the children were analysed qualitatively and quantitatively. The propositions that children used with each photograph were assigned to a particular category. A scoring system, employing a five point scale (Table 2) similar to that used by Yin et al. (2005), was developed to provide an accuracy score for each photograph and therefore a level of the knowledge and understanding held by each year group.

INSERT TABLE 2 ABOUT HERE

For the purposes of categorising the data responses designated scores 2 and 3 were amalgamated. Examples for each level of accuracy can be found in the findings and these were used to guide the responses from other data sets for those concepts.

• Semi -structured Interviews

A sample of children from each age group was selected for a one-to-one semi-structured interview with the intention of enriching the data set further [START_REF] Abdullah | Using interviews to assess children's understanding of science concepts[END_REF][START_REF] Denscombe | The Good Research Guide for Small-scale Social Research Projects[END_REF] and to triangulate information, using a different approach [START_REF] Cohen | Research Methods in Education[END_REF][START_REF] Flick | An Introduction to Qualitative Research: theory, method and applications[END_REF]. Approximately ten percent from each age group were selected to be interviewed and these were chosen to provide a representative sample of the cohort, whilst at the same time representing the variety of ideas presented in the drawings and concept maps. This was achieved using intensity sampling to identify those individuals in whom the phenomenon of interest is strongly represented; in this case knowledge and understanding of micro-organisms or the lack of it [START_REF] Mertens | Research Methods in Education and Psychology: integrating diversity with quantitative and qualitative approaches[END_REF]. The drawings and brainstorms that contained the most accurate, or unusual, answers were selected from each group. This was considered to be a way of representing the full range of views from the [START_REF] Mertens | Research Methods in Education and Psychology: integrating diversity with quantitative and qualitative approaches[END_REF]. Thus, it was hoped that the children selected for interview in this way would have more to discuss and therefore provide richer data than their peers.

The interviews probed children's ideas about, the structure and appearance of microorganisms, the variety of micro-organisms, where they can be found and what they do. In addition probes were introduced; a mouldy peach, food products (yogurt, soy sauce, cheese and bread) and a photograph of compost heap, a person sneezing, and antibiotics were used to explore ideas about decay, health and disease and the technological applications of microorganisms. The interviews were transcribed and the transcripts examined for statements that related to the key conceptual themes within this study; additional and supporting qualitative information was therefore made available. In addition, a numerical tally of how the statements related to the key themes was made, thus providing some quantitative information to support other findings.

• Development of the expressed and mental models [START_REF] Johnson | Constructivism and evidence from children's ideas[END_REF] discuss the difficulty of interpreting children's ideas accurately.

They suggest three methodological principles to evaluate research so that there can be confidence in the reliability and validity of the findings. Firstly that the task(s) children are asked to do is 'neutral'; that is they are accessible to both researcher and child and do not constrain thinking or possible responses. The tasks in this study were open-ended and designed to be suitable for all three age groups. Secondly that any interpretation of responses is made on neutral ground; that is the researcher is aware of the myriad of possible responses.

All data were examined and re-examined to ensure any final analysis of data represented all responses. Finally the children's ideas should be explored from different perspectives through triangulation. This has been achieved here through the use of multiple elicitation techniques.

Using these principles the study has endeavoured to present accurate expressed models that children have about micro-organisms in relation to the concepts explored. The mental models were developed from a subsequent analysis of the data sets by applying the principles of the scoring system categories used in the concept mapping (Table 2) to the qualitative and quantitative data from at least two sources of data for each conceptual area. These scores are based upon the level of accuracy the responses revealed with respect to definition of microorganisms provided earlier and what children should have been taught in school about microorganisms by 14 years. The responses assigned to each score were subsequently categorised as different levels of sophistication to create the mental models for each conceptual area i.e. Emergent = score 1, Transitional = score 2/3 and Extended = score 4.

Findings

The findings are based upon analysis of all elicitation techniques although particular methods facilitated the representation of certain concepts more readily than others, and therefore may form the main source of data [START_REF] Buckley | Investigating the role of representations and expressed models in building mental models[END_REF].

• Classification

Some children in all the age groups in this study classify micro-organisms in a variety of ways (Table 3). The animal and abstract categories are resonant with the findings of previous researchers (e.g. [START_REF] Nagy | The representation of germs by children[END_REF][START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF][START_REF] Vasquez | Les representations des enfants sur les microbes[END_REF]. In particular, 7 year-olds considered micro-organisms to be animals, whereas 11 and 14 year-olds were less certain about micro-organisms actually being animals, but considered them to be animal-like, 'it looks like a cockroach ' (11 year-old). Although, some of the oldest children did show uncertainty about how to classify micro-organisms, 'Um, I think they're maybe animals…Cause they like, they're alive and they're not humans. They could be aliens, but I don't think so' (14 year-old).

INSERT TABLE 3 ABOUT HERE

About one third of youngest children tended to categorise micro-organisms as abstract entities. This age group referred to micro-organisms as things like pieces of dirt, 'germs are little bits of mud that get under your finger nail' (7 year -old). The youngest children in this study seem to have less understanding of micro-organisms as biological organisms compared to the older age groups. As the understanding of biological concepts increases with age [START_REF] Carey | Conceptual Development in Childhood[END_REF][START_REF] Inagaki | Young Children's Naïve Thinking about the Biological World[END_REF][START_REF] Piaget | The Child's Conception of the World[END_REF] awareness of biological species also increases. The idea that micro-organisms are different from other biological groups and that they are often single-celled increased with age and it is possible that direct teaching about micro-organisms may have influenced children's ideas, although a small but significant percentage (19.1%) of younger children drew cell-like micro-organisms, suggesting that some of the youngest children have an appreciation that micro-organisms are quite separate and distinct from plants and animals, even though they have had no formal teaching about this.

INSERT TABLE 4 ABOUT HERE

'Germ', was used universally by 7 year-olds as the sole term for a micro-organism. Older children used a variety of terms. The way in which they were used indicates that the nature of bacteria, viruses and fungi and how they differ from one another is not clearly understood.

' Micro-organism', 'germ' and 'bacteria' were children in a similar fashion to those in Maxted's study (1984). However, others used the terms to refer to different micro-oragnisms and showed awareness that 'micro-organism' and 'germ' are generic terms; this understanding increases with age (Table 4) but some 11 and 14 year-olds used the term 'micro-organism' to denote one super-ordinate organism which can produce other types, resonating with [START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF] findings. Classification of microorganisms is difficult for children across the whole age range and this is not surprising, as taxonomists have disputed the exact classification for many years (Bisset, 1963;[START_REF] Woese | Toward a natural system of organisms: Proposal for the domains Archea, Bacteria, and Eucarya[END_REF]).

• Morphology

What children think micro-organisms look like changes with age, although all categories identified in this study were represented by some children in each age group (Table 5) and are similar to those of previous researchers; for example, [START_REF] Nagy | The representation of germs by children[END_REF] and [START_REF] Vasquez | Les representations des enfants sur les microbes[END_REF]. A more scientific view of micro-organisms develops with age, although more 11 year-olds drew a recognizable bacterial cell than 14 year-olds and this may be due to more recent teaching.

Many of the youngest children consider that micro-organisms look like abstract entities or small animals, and particular species such as, worms, caterpillars, or insects were commonly drawn and referred to, and drawings were frequently anthropomorphised (Figure 1). The 11 year-olds who consider that micro-organisms look like animals tended to refer to insects, whilst both worms and insects were represented in the few animal drawings from 14 yearolds (Figure 1). These children appear to know that micro-organisms are small living things and they have related them to animal species with which they are familiar. Although anthropomorphic ideas decreased with age it is worth noting that these ideas are retained by some, even in the oldest age group (18.0 %), indicating that these views are entrenched, at least for a small percentage of children (author). Cell-like shapes were more commonly drawn by 11 and 14 year-olds suggesting that older children do have some idea that many micro-organisms are unicellular rather than a complex multi-cellular organism and single cells including recognisable bacterial cells were present in some 11 (24.7%) and 14 (16.9%) year-olds drawings (Figure 1 and Table 5). The higher percentage of 11 year-olds drawing recognizable bacterial cells may be accounted for because of recent teaching about microbial morphology whereas the curriculum for the 14 year-olds focuses on micro-organisms in relation to human health. Bacterial morphology, especially bacilli; compared to other micro-organisms is the most commonly represented , and this may be due to exposure to photographs, or drawings in school texts and reference books, or posters in doctors' surgeries, which tend to focus on bacteria. Many of the drawings of micro-organisms as cells, especially those drawn by 14 year-olds attributed the features of typical eukaryotic cells to their drawing, which suggests the influence of current teaching, and some were drawn as a specialised eukaryotic cell e.g. a sperm cell (Figure 1).

INSERT TABLE 5 ABOUT HERE

INSERT FIGURE 1 ABOUT HERE

• Size and scale Like the findings of previous studies [START_REF] Nagy | The representation of germs by children[END_REF][START_REF] Maxted | Pupils' prior beliefs about bacteria and science processes: their interplay in school science laboratory work[END_REF][START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF], there is a consensus view that micro-organisms cannot be seen with the naked eye, and all age groups seem to know intuitively that micro-organisms are small and cannot be seen without magnification. Reference to size in drawings and brainstorms broadly increased with age (Table 6) and the term 'microscopic' was used more frequently by older interviewees. What 'microscopic' means is not generally understood by any of the age groups and familiar small objects such as a speck of dust, the end of a sharpened pencil or a grain of rice to make a comparison were used by 7 and 11 year-olds whilst 14 year-olds used descriptive terms such as 'tiny' or 'microscopic'. Standard measures were used infrequently and inaccurately by some 11 and 14 year-olds. Some attempts to use standard measures, for example, a millionth of a metre, were made by 11 and 14 year-olds. [START_REF] Tretter | Conceptual boundaries and distances: students' and experts' concepts of scale of scientific phenomena[END_REF] found that relative size information rather than exact measures were more readily understood and it would appear that the children in this study are employing these ideas intuitively in an attempt to understand the size of micro-organisms. The findings also accord with [START_REF] Nagy | The representation of germs by children[END_REF][START_REF] Maxted | Pupils' prior beliefs about bacteria and science processes: their interplay in school science laboratory work[END_REF][START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF][START_REF] Vasquez | Les representations des enfants sur les microbes[END_REF] and indicate that, whilst there is a good understanding that micro-organisms are very small and the term 'microscopic' is used widely, there is little real understanding of what this means with respect to the actual size of micro-organisms.

INSERT TABLE 6 ABOUT HERE Everyday experiences, for example, having a viral infection or seeing fungal fruiting bodies were used as reference points to compare the relative size of micro-organisms. The notion of virulence and rapid proliferation was equated to size in all age groups. This thinking, like the findings of Rua and Jones (2006) and was particularly evident with respect to viruses for 11 and 14 year-olds, 'I've seen like, virus I had rashes, chicken pox is a virus and I've had that ……….um, viruses are quite big because they can spread' (11 year-old).

• Living and non-living

Children in all age groups considered micro-organisms to be living (Table 7). A combination of factors, including the 'seven processes', was used to justify why micro-organisms are considered to be alive [START_REF] Osborne | Processes of Life: Primary Space Project[END_REF], although more 7 year-olds compared to other age groups were uncertain about whether they thought micro-organisms were alive.

Progression of understanding about micro-organisms as living things increases with age; more complex ideas about what it means to be alive are more frequent in responses from older children. Cell organelles appear more frequently in drawings of 14 year-olds, but their reasoning reverted to established, more secure knowledge, such as reproduction, respiration or excretion when discussing micro-organisms during interviews, 'Um, they follow certain

INSERT TABLE 7 ABOUT HERE

Like other studies (Maxted, 1884;[START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF]Vasquez, 1983) movement was commonly offered, as an indicator, by children in all age groups of micro-organisms being alive. Reproduction was also cited, especially by 7 and 11 year-olds, but some 14 year -olds also cite this as a reason for being alive. Teleological reasoning led to reproduction being regarded as an aggressive activity, in terms of the speed and rate of microbial increase and their subsequent proliferation, and as a consequence the harm micro-organisms cause humans. Being dangerous, or causing diseases to humans, was a sufficient reason for being alive for some children in all age groups indicating anthropocentric thinking, 'cause if they weren't alive they wouldn't be able to move to kill people' (11year-old).

• Disease and health

Table 8 shows that one of the most common ideas that the children in all age groups hold is the connection between micro-organisms and disease, 'germs are things that can get inside you and you get ill and poorly' (7 year-old); 'micro-organisms can make you sick' (11 yearold). This finding is similar to previous studies , for example, Nagy (1951), [START_REF] Maxted | Pupils' prior beliefs about bacteria and science processes: their interplay in school science laboratory work[END_REF]; [START_REF] Prout | Science, health and everyday knowledge[END_REF] and [START_REF] Springer | Early beliefs about the cause of illness: Evidence against immanent justice[END_REF], who found a pathogenic view of microorganisms was a dominant idea held by individuals of all ages, which [START_REF] Raichvarg | Louis Pasteur -L'empire des Microbes[END_REF] referred to as 'microbe-mania'. More 7 year-olds seem to consider that all micro-organisms are potentially pathogenic, highly infectious and dangerous, 'if a germ gets inside your body you shall be ill' (7 year-old) compared to 11 and 14 year-olds who indicated a greater awareness that not all micro-organisms are pathogenic. Nevertheless they are not very aware of other causes of disease; only two 14 year-olds mentioned genetic disease during the interviews. Others indicated confusion between microbial and non-microbial diseases, or attributed non-microbial disease to a microbial cause, for example cancer and arthritis. Very few specific pathogens were named and micro-organisms were seen to be generically responsible for illness, 'lots are harmful and cause illnesses' (11 year-old); 'infection, they can cause flu cold etc, mouldy bread, a nasty thing that goes into your body and destroys everything' (14 year-old). The majority of children appear to have an exclusively exogenous notion of disease, in which a healthy individual is attacked by micro-organisms and becomes ill. This has implications for children being able to comprehend the nature of genetic disease and, as [START_REF] Simonneaux | Analysis of classroom debating strategies in the field of biotechnology[END_REF] points out, it raises questions about students' ability to understand and appreciate the ethical implications of such techniques as ante-natal screening. These considerations raise many sensitive issues with regard to genetic disease. Biotechnologies, using micro-organisms, that enable testing of those pre-disposed to certain genetic diseases, or other heritable characteristics which may be regarded as undesirable, do indeed pose serious ethical issues.

INSERT TABLE 8 ABOUT HERE

Younger children tend to think that being in the presence of micro-organisms is sufficient to cause infection, 'if you go near the sick child you shall be ill' (7 year-old). Whilst a range of ideas about infection are held by older children, such as coughing, sneezing, touching someone, or eating infected foodstuffs. Contradictory ideas about modes and causes of infection were found in all age groups, 'Um, from like, being, if they get like a virus, then they go out in like the cold air straight away, or the, yeah, like they go in the cold air straight such as colds seems to prevail. It would seem that, as [START_REF] Helman | Feed a cold, starve a fever[END_REF] asserts; the folklore model of infection is very persistent, in particular with regard to the common cold and the term 'cold' reinforces association with the environment. Consequently children employ ontological ideas based on everyday experiences, for example, getting cold or going out with wet hair to explain how they had a cold rather than through infection with a rhinovirus.

• Ecology ( Location)

Previous studies, e.g. [START_REF] Maxted | Pupils' prior beliefs about bacteria and science processes: their interplay in school science laboratory work[END_REF]; [START_REF] Vasquez | Les representations des enfants sur les microbes[END_REF] indicate that the ubiquity of microorganisms is generally understood, and children in this study indicated that micro-organisms could be found in a variety of locations (Table 9). However, unlike Nagy (1951), who found that young children had a restricted idea about where micro-organisms could be found, more of the oldest children in this study seem to have a more restricted notion that focuses on human beings, as the principal point of microbial location. Connection with humans seems to increase rather than decrease with age and this may be due to the curriculum that focuses on micro-organisms as agents of (human) disease in early secondary school. The notion of ubiquity seems to be more predominant in 11 year-olds' thinking, 'you might, you could find them anywhere across the world. Could be the cleanest place on the planet and you could still find bacteria there' (11 year-old). Association with unpleasant and dirty conditions is a frequently held idea and the link between this and the threat micro-organisms pose to human health is well established in all age groups. Dirty places, rubbish, dustbins and soil are all cited by children in every age group as places where micro-organisms can be found.

Compost heaps and sewage works were also regarded by many children as dirty and unhygienic and they asserted that micro-organisms would, therefore, be found in these places in large numbers. All age groups associate micro-organisms with decay to some extent, although 7 and 11-year olds focus on food spoilage rather than other forms of decay making a connection with micro-organisms as a threat to health. Therefore it is not surprising that decay is considered negatively. Compost heaps are also viewed, anthropocentrically by 7 and 11 year-olds as dangerous places due to a potential risk from microbial infection.

INSERT TABLE 9 ABOUT HERE

Table 10 shows children's ideas about decay. Progression about microbial causes of decay occurs between 7 and 11 years but this does not appear to continue to develop. [START_REF] Leach | Children's ideas about ecology 2: ideas found in children aged 5-16 about the cycling of matter[END_REF] noted that children aged between 5-16 years did not readily cite micro-organisms as the agents of decay but children in this study readily regard micro-organisms as a cause of decay. However the role of micro-organisms in decay is not generally understood and few children seem to know, even at a basic level, that micro-organisms break down organic matter. Those who did offer explanations suggested that micro-organisms feed on, eat or take over the item, 'if you leave bread for a long time it turns mouldy and germs bite into it' (7 year-old). Alternative ideas, for example, that items will decay 'naturally' as a result of time also seem to stay at a similar level across the age groups indicating that certain ideas persist despite formal teaching or extended personal experience.

INSERT TABLE 10 ABOUT HERE

Everyday experiences of food decay seem to give rise to ontological reasoning about the fate of decaying matter. All age groups considered decaying items would disappear with, or without, microbial activity, although some items, for example, a peach stone was regarded as too hard to decay and would remain intact. Furthermore, the disappearance of some items was regarded as a beneficial outcome of decay, as it would help to clear the environment of such things as leaves in autumn, 'dead bodies and in Autumn when all the leaves fall cause otherwise there'd be lots of leaves everywhere………Um, because then everything is clear and it, the soil can be used for everything to start again' (11 year-old). The end products of decay in the compost heap were 'soil' or 'compost' and some 11 and 14 year-olds understand that the soil would be enriched, or that 'nutrients' would be present, as a result of decay, but and transformation into inorganic products was not considered.

• Technological applications

Previous research shows that the use of micro-organisms by humans to manufacture food [START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF]Williams and Gillen, 1991), for medical products [START_REF] Maxted | Pupils' prior beliefs about bacteria and science processes: their interplay in school science laboratory work[END_REF][START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF], or for environmental benefit is poorly understood. Findings in this study indicate that food production is more commonly recognised as a technological application of micro-organisms compared to both medical or environmental uses and acknowledgement of their use increases with age (Table 11). However, the metabolic processes involved in production of bread, beer and yogurt were not generally understood, and cheese was the only other food product mentioned that might use micro-organisms in its manufacture. Yogurt was associated with sour milk, or allowing the milk to 'go off' by some 14 year-olds indicating a lack of awareness of the role of micro-organisms in its production. Yeast seems to be considered as a 'universal' micro-organism used in food production, which is probably due to limited experience of science practical work and the influence of food technology lessons.

Micro-organisms were connected with food as potential contaminants by all age groups, especially 7 year-olds, 'Um, because if germs actually made that food, when you have it, it will make you ill' (7 year-old). Although 11 and 14 year-olds were increasingly aware of the use of micro-organisms in food manufacture the majority of responses also indicated that they too consider micro-organisms mainly as a source of food spoilage and therefore dangerous. The use of micro-organisms in the production of vaccine and antibiotics is not generally understood by any age group and when this application is recognised it is at a simple level; for example, 'good' micro-organisms being placed in vaccine or antibiotics as the active agent. These findings are similar to those of [START_REF] Simonneaux | A study of pupils' conceptions and reasoning in connection with 'microbes',as a contribution to research in biotechnology education[END_REF]. The level of alternative ideas also remains relatively stable across all age groups, indicating that some ideas are resistant to change. The specificity of vaccines or antibiotics was not explored and more complex ideas, such as killed or attenuated micro-organisms, or less virulent species used in vaccines were mentioned by only a small minority of children in all age groups. Vaccines and antibiotics are more generally thought of as medication, which is not surprising as this is how the majority of children will have encountered them.

INSERT TABLE 11 ABOUT HERE

The role of micro-organisms in benefitting the environment is poorly understood and responses to photographs of a compost heap, sewage works, or during interviews suggest that children are unaware of the environmental applications of microbial activity which accords with the findings of [START_REF] Leach | Children's ideas about ecology 2: ideas found in children aged 5-16 about the cycling of matter[END_REF]. Very few children, in any age group, know about the role of micro-organisms in the purification of sewage. Ideas about sewage works being hazardous to human health because of the presence of micro-organisms are retained by all age groups. The positive role of micro-organisms in the environment as a lynch pin in the cycling of matter and as an essential factor in maintaining the ecological balance is not understood by the majority of children in this study.

• Summary

Many ideas children hold about micro-organisms are broadly similar across the three age groups, for example, micro-organisms as the cause of disease. Negative ideas about microorganisms prevail in all age groups, especially in connection with the threat they pose to this aspect of children's thinking seems to reduce with age, anthropocentric ideas are retained by a substantial minority (18%) of 14 year-olds.

The ideas that children have expressed about micro-organisms in this study largely concur with the findings of previous studies. This suggests that children's ideas currently are no different to their earlier counterparts and that context or increased teaching does not have a major effect. However the findings provide a more comprehensive overview of these ideas than previous studies and this may be of use to science educators in different countries or at different points in time.

Children's mental models of micro-organisms

Generalised hierarchical mental models (Table 12) have been derived, from the categorization of the data shown in the findings for each of the seven themes explored in this study as explained earlier. The ideas with regard to each key theme specified vary in sophistication and the resulting mental models were categorised as Emergent (score 1), Transitional (scores 2 and 3) or Extended (score 4).

The spectrum of these different levels of sophistication is represented in the ideas of each age group to a greater or lesser extent (Tables 34567891011). These models, therefore, offer a generalised portrayal of the ideas held about micro-organisms for the age groups investigated. However, as noted previously, mental models are considered as the personal ideas of individuals; they are therefore idiosyncratic. In attempting to form a model of what each age group in this study thinks about particular aspects of micro-organisms, it is acknowledged that any model offered is a generalization, that any particular individual may hold a subtly different mental picture from those presented here, and that some ideas cannot be included within the generalised models. Nevertheless, the models presented here are formed on the basis of the

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Discussion and conclusions

• The generalised mental models

The models for each theme represent different levels of sophistication in conceptual understanding. Progression is defined as a gradual change from one level of thinking to another. In terms of children's ideas and their learning, this may be regarded from a constructivist perspective as increasing, or assimilating, new ideas into a mental model, thereby strengthening and deepening conceptual understanding [START_REF] Johnson-Laird | Mental Models[END_REF][START_REF] Piaget | The Child's Conception of the World[END_REF]. The findings indicate that extended models are more frequently held by 11 and 14 year-olds for several key themes, indicating that progression does occur for some children between 7 and 11 years with regard to these concepts (Tables 34567891011). A higher proportion of older children hold these more sophisticated models, which would indicate a conceptual change and therefore progression of ideas but little progression seems to occur after 11 years in several key themes, notably, disease, decay, and technological applications of microorganisms. This is surprising in terms of children's understanding of biological phenomena that is thought to increase with age [START_REF] Carey | Conceptual Development in Childhood[END_REF][START_REF] Piaget | The Child's Conception of the World[END_REF]. Furthermore even though progression seems to be most pronounced between 7 and 11 years, it is worth noting that some of the youngest children hold advanced ideas that are congruent with those of their older counterparts. However, it is noticeable that extended models are rarely held by the [START_REF] Carey | Conceptual Development in Childhood[END_REF] is difficult to accomplish as children retain previous ideas to avoid cognitive dissonance [START_REF] Driver | Students' conceptions and the learning of science[END_REF][START_REF] Whitelock | Children's Learning and Alternative Conceptions in Science[END_REF]. In these circumstances conceptual change is less likely to occur [START_REF] Driver | The Pupil as Scientist? Milton Keynes[END_REF]. The findings indicate that progression does not occur simply as a result of age, maturity, or educational experience in a linear fashion and that learning is not generally so simplistic (e.g. [START_REF] Carey | Conceptual Development in Childhood[END_REF][START_REF] Driver | The Pupil as Scientist? Milton Keynes[END_REF][START_REF] Harlen | The Teaching of Science in Primary Schools[END_REF].

• Implications for curriculum development

The generalised mental models highlight particular challenges for curriculum developers and may help to inform curriculum development. Considerations for the curriculum include how to capitalise on informal learning especially at an early age, the need to refocus the curriculum at early secondary school to include aspects of microbiology that have been explored in this study rather than only those dealing with human health and to make a case to develop the curriculum so that episodes of learning about micro-organisms are more frequent and topic-based across the age range. Some very young children appear to understand complex concepts about micro-organisms.

However, there is a clear mismatch between children's ability to comprehend these ideas and curriculum content. The current science curriculum in England for 7 year-olds does not include any specific reference to micro-organisms and yet children at this age do have a level of knowledge and understanding that could be used as the basis for formal learning.

Adaptation of the curriculum would enable children to learn about micro-organisms earlier than they do at present. This would mean that, rather than starting 'cold' in upper primary this curriculum would have a platform of formal learning episodes on which to build. Many 14 year-olds do not have the expected knowledge and understanding about microorganisms and misconceptions remain. Curriculum planners may need to consider how to provide more opportunities to teach about micro-organisms, for example by including microbial morphology and variation, and technological applications of micro-organisms thus expanding the breadth of study rather than the current focus on micro-organisms in relation to human health for this older age group. This would build more coherently on the requirements for 11 year-olds in upper primary school and provide opportunities to revisit topics to facilitate a restructuring of some children's mental models. These alterations may improve levels of knowledge and understanding about micro-organisms so that progression does not plateau after 11years to enable the majority of children to make further progress. As a consequence they may be in a better position,later in their schooling, to understand more conceptually challenging ideas for example, genetic engineering and its social and moral implications [START_REF] Hill | What ideas do students associate with 'biotechnology' and 'genetic engineering[END_REF][START_REF] Lock | Educating the 'New Pasteur[END_REF][START_REF] Schaechter | Microbiology in the 21 st Century: Where are we and where are we going? A report for the American Academy of Microbiology[END_REF][START_REF] Simonneaux | Analysis of classroom debating strategies in the field of biotechnology[END_REF]. . . (Furthermore, many of the conceptual themes explored in this study are relevant to other aspects of science and the wider curriculum. Planners might reconsider the place of microbiology within the curriculum across the whole age range so that teaching about microorganisms is more closely integrated within broader aspects of science and other subject areas, such as health, ecology and biotechnology. Developing schemes of work that incorporate the importance of micro-organisms within ecosystems and the technological applications of micro-organisms would provide children with the opportunity to gain a better understanding of the role and importance of micro-organisms per se within these fields of knowledge, and as a result they may also develop a more comprehensive understanding of (Author, 2006;[START_REF] Gillen | Dinner date with a microbe[END_REF][START_REF] Jones | Conceptions of Germs: Expert to Novice Understandings of Microorganisms[END_REF][START_REF] Lock | Educating the 'New Pasteur[END_REF][START_REF] Schaechter | Microbiology in the 21 st Century: Where are we and where are we going? A report for the American Academy of Microbiology[END_REF][START_REF] Simonneaux | Analysis of classroom debating strategies in the field of biotechnology[END_REF].

• Consequences for teaching and learning

One of the tenets of a constructivist view of learning is that children do not come to a learning situation with an 'empty head' and that everyday experiences influence children's learning (e.g. [START_REF] Driver | Students' conceptions and the learning of science[END_REF][START_REF] Von Glasersfeld | Cognition, construction of knowledge and teaching[END_REF]. The models clearly illustrate that children in all age groups have a wide range of ideas embracing the key concepts explored in this study. Furthermore, the ideas that children hold are not necessarily in line with accepted scientific thinking. It is clear from the models that some children in all age groups hold ideas that depart from the scientifically accepted view of micro-organisms. The fact that some 14 year-olds have emergent mental models about particular aspects of micro-organisms suggests that some knowledge is entrenched and highly stable. These alternative ideas appear difficult to change and are retained despite formal teaching, and they are often used to explain concepts which indicate ontological reasoning on the part of these children. It is also worth noting, that even the extended model that has emerged, falls short in many respects of the scientific view of micro-organisms and what 14 year-olds might be expected to know and understand as a result of learning and teaching. These findings have implications for children's future progress in learning about microbiology, as particular concepts may appear unrelated to their own mental models; the gap between what the children think and what is being taught may be too great so that they are unable to resolve potential confusion. In these circumstances, children may prefer to retain their previously held ideas, making conceptual change less likely because of the lack of cognitive dissonance [START_REF] Driver | The Pupil as Scientist? Milton Keynes[END_REF], or dissatisfaction with their own model [START_REF] Strike | Conceptual change and science teaching[END_REF].

Learning about micro-organisms appears to occur in a range of contexts, which includes home and school. example, being taught to wash hands after visiting the lavatory, television advertisements and media portrayals of micro-organisms, or being ill. By capitalizing on these informal learning experiences, and making positive use of them from an early age, worthwhile integration of both formal and informal contexts can be achieved. Children could have the opportunity to consider some of their pre-conceptions by discussing their experiences, such as being ill, visiting the doctor or dentist, or discovering mouldy bread or rotting leaves and exploring the role of micro-organisms in these events.

Strong emotional connotations about micro-organisms are evident in the data and the influences of the experiences just described are likely to have made a contribution to children's views, suggesting that children's ideas are to some extent socially mediated.

Developing social interaction, as an aspect of pedagogy, by offering opportunities to discuss and reflect on currently held ideas about micro-organisms would allow children to challenge their peers and themselves through the medium of discourse. For example; 11 year-olds could be provided with cartoon images and electron micrographs of micro-organisms and be asked to discuss how best to portray micro-organisms to the general public. Similarly 14 year-olds could discuss newspaper articles that portray micro-organisms as dangerous or harmful and compare them with a scientific account. These activities may help to eradicate the negative perceptions of micro-organisms held in all age groups by encouraging a positive conception of micro-organisms.

Findings also suggest that children divorce science taught in school from everyday ideas, for example, ideas about what causes the common cold. Compartmentalising learning within specific contexts enables different ideas to be held contemporaneously and avoids dissonance [START_REF] Driver | Students' conceptions and the learning of science[END_REF][START_REF] Whitelock | Children's Learning and Alternative Conceptions in Science[END_REF]. In these circumstances conceptual change is less likely to occur [START_REF] Driver | The Pupil as Scientist? Milton Keynes[END_REF]. As [START_REF] Novak | Meaningful learning: the essential factor for conceptual change in limited or inappropriate propositional hierarchies leading to empowerment of learners[END_REF] indicates, meaningful learning will only take place when there is reciprocal transfer between ideas derived from different contexts, which enables children to make use of ideas derived from the science learnt in the classroom to solve everyday problems. Everyday experiences such as not being able to see microorganisms, or the severity of different illnesses, suggest that ontological reasoning gives rise to children's ideas about the size and scale of micro-organisms. The notion that microorganisms are 'microscopic' is generally recognised by children in all age groups. However, the scale and relative size of different micro-organisms is poorly understood. Integrating learning with other aspects of the curriculum; for example, mathematics and geography from the earliest age could provide children with a better understanding of what microscopic really means.

A greater emphasis on practical work that introduces and sustains work about microorganisms, from 7 to 14 years may also help to maintain progress [START_REF] Lock | Educating the 'New Pasteur[END_REF]. For example; making bread and yogurt at 7 years old would provide an introduction to the uses of micro-organisms. Children at 11 years could build on these experiences and explore the fermentation process more thoroughly, including the need for sterile conditions; for example, when making yogurt or ginger beer. Children might then understand the uses of beneficial micro-organisms and those that are not beneficial under certain conditions. The role of micro-organisms as decomposers could be investigated by exploring what occurs in a compost heap. Children at 14 years would be in a position to undertake further practical work that explored the conditions required for these microbial activities. This would enable them to begin to develop their understanding of the metabolic processes of the microorganisms involved.

In conclusion, children learn about micro-organisms in a range of contexts and from a variety of experiences. Further work is needed in order to discern how, and to what extent these different contexts affect their ideas. However the generalised mental models presented may provide a useful reference point of children's ideas across the 7 to 14 year-old age range to Deleted: Providing ways of developing ideas through argumentation in science is thought to be effective in challenging children's conceptual understanding (e.g. Newton, [START_REF] Novak | Meaningful learning: the essential factor for conceptual change in limited or inappropriate propositional hierarchies leading to empowerment of learners[END_REF]Osborne, Eduran & Simon, 2004;Simon, Eduran & Osborne, 2006). Children could be encouraged to debate issues such as the cause of the common cold or microbial virulence. Using argumentation more frequently, as a pedagogical tool, could enable children to develop a more profound understanding of micro-biology. ¶ vaccine and antibiotics are antimicrobial agents and kill pathogenic micro-organisms, cure (human)diseases caused by micro-organisms micro-organisms are dangerous to humans and are not beneficial to the environment, compost heaps and sewage works are dangerous because of the presence of micro-organisms and pose a threat to human health micro-organisms are used to make certain food stuffs, yeast is the universal micro-organism used in the production of food micro-organisms are used in the manufacture of vaccine and antibiotics, vaccine and antibiotics contain 'good' micro-organisms to fight or kill 'bad' micro-organisms that cause (human)disease, vaccine can prevent further infections. micro-organisms can be useful to decompose matter to provide nutrients for the soil, compost and sewage is used by micro-organisms as a medium in which to grow and multiply and compost heaps and sewage works are therefore a potential source of danger to humans due to the large number of micro-organisms present some microbial metabolic activities enable them to be used in the production of food stuffs micro-organisms are used to produce vaccine and antibiotics, dead, attenuated, less pathogenic micro-organisms are used in vaccine to prevent diseases acquired immunity conferred as a result of vaccination, antibiotics not effective on viral infections micro-organisms decompose organic matter and may help the environment as 'cleaners' e.g. in the purification of water and removal of organic 'litter' Page 50 of 50 URL: http://mc.manuscriptcentral.com/tsed Email: editor_ijse@hotmail.co.uk

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  Deleted: <#> How are micro-organisms conceptualized, in terms of knowledge and understanding, by children at 7, 11 and 14 years? ¶

  things….such as reproduction, um, excretion, things like that…….Um, I think they, they respire, I think' (14 year-old).

  away. They kind of like catch a cold' (11 year-old); 'Someone else probably coughed in front of her and the germs went in her mouth.… I got it on Sunday, I'd been… Oh, I'd been at the beach! And I'd been in the water loads and got a cold cause I got cold' (14 year-old). A germ theory of disease held in conjunction with a non-germ theory, or a biomedical model abandoned in favour of a folklore model of disease when talking about common illnesses Page 17 of 50 URL: http://mc.manuscriptcentral.com/tsed Email: editor_ijse@hotmail.co.

  human health. These and other anthropocentric ideas are held by all age groups. Even though

  micro-organisms that children in this study hold. They therefore can be regarded as coherent representations of children's knowledge frameworks concerning microorganisms. As such the models may offer insights into children's ideas about microorganisms and therefore they are potentially a useful reference tool for curriculum developers to use when considering curriculum content, as well as for teachers when planning teaching sequences.

  in any age group suggesting that restructuring of ideas

Formatted

  Developing schemes of work that incorporate the importance of microorganisms within ecosystems and the technological applications of microorganisms may help to maintain progress about these concepts Deleted: Children should then be in a better position to begin to understand the even more conceptually challenging ideas such as, the role of micro-organisms in genetic engineering a Deleted: nd cycling of nutrients. ¶

  that this important aspect of the science curriculum is effectively taught and adequately learned.

  Figure 1: Examples of drawings

  Food production = photos of bread ( Br) , beer ( Be) and yogurt (Yo) Medical = photos of vaccine (V) and antibiotics ( A) Environmental = photos of compost heap ( CH) sewage works ( SW)

  ). Quantitative tallying of the different categories was undertaken to provide frequency and percentage data for each category.

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  However, this method provided an excess of 'cases'. Extreme, or deviant, sampling in which unusual or atypical responses was employed to reduce the cases for each age group. This sampling method is thought to illuminate the normal situation by studying the extraordinary because they can provide examples of the most clear cut examples of the phenomena being studied

	cohort.
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  Common life experiences appear to have influenced children's ideas, for

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Table 1 : Categories for analysis of drawings and brainstorms

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	Appearance /	Terms	Size and scale	Living	Location	Microbial
	morphology					activity
	Amorphous /	Micro-organism Small drawings	Living and/or	Everywhere	Creates an
	amoeboid			presence of cell		immune
				structures		responses
	Bacterial cell	Germ	Small	Living	In/ on humans	Some are
				processes		pathogenic
	Eukaryotic cell	Bacteria	Microscopic/	Possibly living /	Dirty/	All are
			requires	non-living	unhygienic	pathogenic
			magnification to		places
			be seen
	Animal/ animal	Virus	Actual size		Animals
	like e.g. worms,
	insects etc
	Anthropomorphic	Fungus/ mould
	e.g head, eyes,
	Abstract e.g. dots,
	squares, lines
	Other e.g.
	cartoons

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Table 2 : Scoring system for photograph association concept maps

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	Statement type	Score
	Photograph not used / Photograph used without a statement	0
	Non-scientific / alternative statement	1
	Appropriate statements	2
	More detailed / accurate statements	3
	Advanced statements /more scientifically detailed	4

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Table 3 Classification

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	Data source		Drawings			Interviews		Scoring
		Total may be more than 100% due to				for
			multiple drawings					mental
								models
	Age group	7	11	14	7	11	14
		n =159	n = 166	n = 89
		Frequency	Frequency	Frequency	n	n	n
		%	%	%	=10	= 11	= 9
	Cell like/ single	30	87	63	0/10	7/11	5/9	4
	cells	19.1	52.4	70.9
	Animals/	87	52	17	6/10	2/11	4/9	2/3
	anthropomorphic	54.7	31.3	19.1
	e.g., worms,
	insects
	Abstract e.g. dots,	48	36	14	3/10	0/11	0/9	1
	lines,	30.2	21.7	15.7
	Other e.g. fantasy,	9	5	11	1/10	2/11	0/9	1
	cartoons	5.7	3.0	12.4

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Table 4 Terminology

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	Data source	Drawings		Brainstorms	Interviews	Scoring for
	Total may be more than 100% due to	Total may be more than 100% due to	Total may be more than	mental models
		multiple terms used		multiple terms used	100% due to multiple
					terms used
	7	11	14
	n =159	n = 166	n = 89

Table 5 Morphology

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	Data source		Drawings			Interviews	Scoring for
		Total may be more than 100% due to			mental models
			multiple drawings
	Age group	7	11	14	7	11	14
		n =159	n = 166	n = 89	n =10	n = 11	n= 9
		Frequency	Frequency	Frequency
		%	%	%
	Single cell/	10	41
	bacterial cell	6.3	24.7
	e.g. bacillus.
	coccus
	Amorphous/	20	46
	recognisable	12.8	27.7
	plant/ animal
	cell
	Animal like	43	35
	e.g. worm,	27.0	21.1
	insect
	Abstract e.g	48	36
	dots, triangles	30.2	21.7
	Other e.g.
	cartoons	9
		5.7

Table 6 Size and scale

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	Data source		Drawings			Brainstorms			Interviews	Scoring
										for
										mental
										models
	Age group	7	11	14	7	11	14	7	11	14
		n =159	n = 166	n = 89	n =139	n = 164	n = 78	n =10	n =11	n= 9
		Frequency	Frequency	Frequency	Frequency	Frequency	Frequency
		%	%	%	%	%	%
	Microscopic/	14	22	5	11	39	35
	requires	8.8	13.3	5.6	7.9	23.8	44.9
	magnification
	Small	8	16	8	5	33
		5.0	9.6	9.0	3.6	20.1
	Small	42	65	35	-	-
	Drawings	26.4	39.2	39.3

Table 9 Location

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	Data source		Drawings			Brainstorms			Interviews	Scoring
										for
										mental
										models
	Age group	7	11	14	7	11	14	7	11	14
		n =159	n = 166	n = 89	n =139	n = 164	n = 78	n =10	n = 11	n= 9
		Freq	Freq	Freq	Freq	Freq	Freq
		%	%	%	%	%	%
	Everywhere	0	3
		0	1.8
	Humans	9	17
		5.7	10.8
	Dirty	7
	/unhygienic	4.4
	places
	Animals	6
		3.8

Table 10 Decay

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	Data source					Concept maps			Interviews	Scoring
			Photos of compost heap = CH, mouldy bread = MB, sour milk = SM,	for mental
									models
	Age group		7			11		14	7	11	14
			n = 173			n = 169		n = 103	n=10	n = 11	n= 9
			Frequency			Frequency		Frequency
			%			%		%
		CH	MB	SM	CH	MB	SM	CH
	MOs cause decay that	0	0	0	2	7	2	2
	can be beneficial and	0.0	0.0	0.0	1.2	4.1	1.2	1.9
	detrimental
	MOs cause decay	12	74	32	35	96	72	28
		6.9	42.9	18.6	20.7	56.8	42.6	27.2
	MOs cause decay and	47	35	27	26	22	31
	this is harmful	27.2	20.2	15.6	15.4	13.0	18.3

Table 11 Technological applications

 11

	Data source	Concept maps

Table 12 : Generalised mental models of children's ideas about micro-organisms

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		Key theme	Emergent	Transitional	Extended
	Classification
	o	Grouping	non-biological entities, variation is based upon	animal or animal-like, variation within	single celled living organisms and distinct from
			the level of virulence and the threat to human	groups is based upon appearance and	plants and animals, variation within groups is
			health	activity which includes harm done to	generally based upon appearance and activity
				humans
	o	Terminology	single term used to one group generally	multiple terms used to refer to different	multiple terms used to refer to different groups
			referred to as germs	groups which include micro-organisms,	within the umbrella term 'micro-organism' these
				bacteria, germs and possibly fungi and	include bacteria, fungi, viruses, 'germ' is also a
				viruses	generic term
	Morphology
	o	External	little animals, usually invertebrates and often	amorphous single 'cell' or recognisable	single cells, some recognisable as bacterial
		appearance	anthropomorphised or human-like characters or	plant or animal cell, may have external	cells, may have external features e.g. cilia/
		and features	abstract often geometric shape,	features e.g. hairs	flagella
			anthropomorphic external features which may
			illustrate a harmful appearance
	Size and scale	Small, actual size not understood, size	small / microscopic, size explained using	microscopic, requires magnification to be visible,
			sometimes related to virulence	everyday objects or specific vocabulary	size sometimes referred to in standard
				as a reference point	measures (but not necessarily understood)
	Living and non living	non living / possibly living	living, evidence-based on living	living, presence of cell structures/organelles
				processes especially movement and	included as evidence of living
				reproduction, as well as anthropocentric
				ideas, e.g. harm caused to humans
	Disease, heath and hygiene	all micro-organisms are potentially pathogenic	not all micro-organisms are pathogenic,	not all diseases are caused by micro-organisms,
	o	Disease and	and highly infectious, especially to humans,	micro-organisms cause diseases,	some micro-organisms are pathogenic, the
		Infection	levels of virulence are not differentiated, illness	especially in humans, levels of virulence	symptoms of illness are as a result of immune
			is a spontaneous reaction to the presence of	are not recognised, modes of infection	response to microbial activity, focus on human
			micro-organisms, contradictory ideas about	focus on human transmission,	illness, levels of virulence may be recognised,
			modes of infection exist	contradictory ideas exist about modes of	various modes of infection are known although
				infection	contradictory ideas still exist
	Ecology
	o	location	micro-organisms are associated with dirty,	micro-organisms can be found	micro-organisms can be found everywhere
			unhygienic places and animals, and as a result	everywhere but especially noted for
			are a hazard to humans, micro-organisms	association with humans and are
			exhibit free will and emotions about their	potentially harmful, micro-organisms
			location	exhibit free will and emotions about their
				location
	o	decay	decay is a result of age or physical conditions,	micro-organisms associated with decay	decay requires a combination of environmental
			decaying items ( food, compost, sewage) are	items, cause decay by 'eating' items,	and physical factors for microbial growth,
			dangerous especially to humans and can cause	decaying matter (food, compost or	decaying item will change and eventually
			illness because of the presence of micro-	sewage) can pose a threat to human	disappear, decay can be beneficial as a litter
			organisms, decaying items 'go bad' , change	health because of the presence of micro-	prevention mechanism or to provide nutrients in
			physically and may eventually disappear, all	organisms, some forms of decay are	the soil

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  of decay are regarded negatively and positive role of micro-organisms in decomposition not recognised regarded negatively, decaying items change physically and eventually disappear but some items are too hard to decay, the soil is the main end point for decaying items

	Technological applications
	o	food	micro-organisms cannot be used to make food
			because they are dangerous ( to humans)
	o	medical
	o	environmental

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