Date: 28/04/14. Day: Monday. Class: 5 th year biology. Class length: 80 mins. Subject: Bacteria. Topic: Bacteria friend or foe?

Transcription

1 Date: 28/04/14 Day: Monday Class: 5 th year biology Class length: 80 mins. Subject: Bacteria Topic: Bacteria friend or foe? Introduction The organisms in the biosphere are divided into 5 kingdoms. The kingdoms are based on internal and external features. The kingdom prokarya include bacteria and cyanobacteria. Bacteria are microorganisms found in all parts of the biosphere. Since bacteria can be found in all parts of the biosphere they must be able to gain nutrition in many different ways. These ways are autotrophic (chemosynthetic or photosynthetic) or heterotrophic (parasitic or saprophytic). They reproduce asexually or sexually and can be classified as being aerobic or anaerobic. The economic effects of bacteria are huge from streptococcus used in yoghurt making to streptomycin in making antibiotics to vibrio bacteria causing cholera and mycobacterium causing tuberculosis. Antibiotics are powerful agents in the fight against infectious disease caused by pathogenic bacteria. Resistance is a problem when a few members of a bacteria population resist the effects of antibiotics. Resistance is due to mutation. Excessive use of antibiotics removes non resistant strains leaving the resistant bacteria to flourish. As a result more powerful antibiotics must be developed. Such items of animal feeds can bring antibiotics into the human food chain which increases the chances of resistance by bacteria. Over use of antibiotics through non essential antibiotic prescriptions by medical professionals and not completing a prescription can also lead to resistance. Health and safety procedures must be adhered to by all members of the public when at home and in public places to prevent the spread of infectious diseases. Previous knowledge and experience Pupils should have some information from the previous lesson an introduction to bacteria cell structure, nutrition and growth. They should have some information about bacteria from television advertisements for safe food, and illnesses caused by bacteria. I expect pupils to have a good understanding of the difference between viruses and bacteria from completing the Junior Certificate Science course. Pupils have already studied cells, enzyme, diffusion and osmosis. I expect pupils to be able to come up with some advantages and disadvantages of bacteria. This is covered in the junior certificate syllabus 1C 8 microbiology and biotechnology. I don t expect pupils to have a good understanding of immunology or how bacteria reproduce. Pupils should have some understanding of how bacteria spread and how to slow their spread. I expect pupils to have many misconceptions about bacteria.

2 Aims To introduce bacterial reproduction and economic advantages and disadvantages, student s misconceptions about bacteria will be addressed. Objectives/learning outcomes Pupils will be able to pinpoint their misconceptions about bacteria. Pupils will be enabled to surmount their misconceptions about bacteria which will strengthen their understanding of the topic. Pupils will be encouraged to foster an interest in and will appreciate the importance of bacteria in the natural world and in biotechnology. Students will be enabled to improve their communication skills as they will work cooperatively in groups. Pupils should be able to use numeracy skills to calculate the no. of bacteria produced over a period of time. Subject matter The student will learn how bacteria reproduce through binary fission and how their fast rate of reproduction can evolve with mutations. The advantages and disadvantages of bacteria will be observed. Pupils will learn how bacteria can cause infection and how antibodies work. Pupils will carry out an experiment to collect bacteria from the classroom environment and personal items such as mobile phones, coins, hair, skin and desk tops and door knobs using swaps. These swabs will be spread out on agar dishes and bacteria grown in an incubator. Students will observe agar dishes with antibiotics discs and bacteria a zone of inhibition will be observed. Students will see how bacteria is prevented from spoiling food, used in producing food and bacteria s effects on humans. Resources Mini white boards, loop game with bacteria facts, Agar dishes with nutrient agar, swabs, Antibacterial disinfectant, power point, projector and slide show. YouTube video. Assessment I will assess what the pupils have learnt throughout the class by observation and teacher questions. I will use a series of higher and lower cognitive questions along with various levels of Blooms Taxonomy. I will test pupil s knowledge through ascending levels of challenging questions. The practical element of the class will allow me to carry out an assessment for learning and observe what the pupils have learnt about bacteria. I will use a matching game at the end of the class as assessment of learning from the present and previous lesson Classroom management All school bags will be left outside the lab room door. Where pupils will be engaging in group work they will be placed in groups of no more than three where possible so as to ensure that all pupils are involved in the activity. Larger groups may lead to disruption to the learning environment, as pupils

3 may become involved in off task conversations. Where possible a buddy system will be incorporated into group work where stronger and weaker pupils are paired up. Safety: See risk assessment sheet Identification strategies/ resources used to identify misconceptions in the classroom. A common misconception that students have is that microbes are not living things. Bacteria are viruses is also a misconception. All bacteria are bad for you is also a common misconception. Students have difficulty conceptualising microbes as agents of change (example microbes and decay they often think decay is an inherent property of the object itself rather than being transformed by microbes). All diseases are caused by bacteria is also a misconception. A mutation modifies an individual s own form during its life rather than only its germ cells and offspring. Students may not know what asexual reproduction is they may only believe that sexual reproduction is the only form of reproduction that occurs (M.D.E.S.E 2005). Strategies to overcome misconceptions Pupils will revisit the characteristics of life and classify bacteria into the category of either living or non living. Students will name some types of bacteria and describe whether they are good or bad for humans. A bottle of pro biotic yogurt is shown to pupils to prove that there are good bacteria living inside of humans. A video of asexual reproduction (budding) of yeast will be shown to pupils so as pupils can visualise how budding occurs. To illustrate that all bacteria are not bad for humans an analogy comparing bacteria compared to trees in a power point presentation will be used.

4 Time Pupil activity Teacher activity Assessment/ references Set induction goal conceptions Misconceptions in relation to set induction Microbes are living things. Bacteria are not virus Microbes are not living All bacteria are bad for you is also a common things. misconception. Bacteria are a virus Students have difficulty conceptualizing All bacteria are bad for microbes as agents of change. Microbes and you decay is often viewed as an inherent property Decay is an inherent of the object itself rather than being property of the object transformed by microbes. itself rather than being transformed by microbes. 5mins 10mins Pupils observe a recap of the previous lesson on the white board. Pupils will receive a white board and will answer questions from the previous lesson as a recap and uncover their misconceptions about bacteria. Teacher delivers a brief summary of the main points from the previous lesson. Pupils handed a white board to write down answers. A short refresher activity is a useful activity as a recap of a previous activity (Kyriacou 2007). Questions What are bacteria? Are bacteria harmful or beneficial? If so how? How are bacteria and viruses different? What roles do bacteria have in nature? How many cells do bacteria have? Draw a bacteria and an animal cell and compare the two? How many shapes do bacteria occur in? Are there more human or animal cells in our body? Teacher takes a sample of answers from pupils to probe for misconceptions. Sample answers are taken and written on the board for pupils to observe the answers. The examination of misconceptions is of the utmost importance for a constructivist self correcting classroom (Petty 2009). 5mins Pupils will observe a video on bacteria misconceptions and compare their answers to answers on the video. Teacher probes pupils learning from the video through questioning. Correct and incorrect answers will be further probed by pupil questioning to elaborate on why other answers are incorrect. Explain Students provided with definitions about bacteria to unearth and correct misconceptions.

5 5mins Pupils will observe a power point presentation on bacteria and divide up into groups of three to come up with the correct answer to the concept cartoon question. Pupils give reasons as to why the other answers are incorrect. Pupils answer questions on the white board Questions What advantage does asexual reproduction give bacteria? How are bacteria passed between people? Pupil s knowledge and misconceptions of bacteria further probed prior to the practical aspect of their lesson. Engage The use of the video is used to grasp pupils attention The ability to take in information can be increased by alternating between sight and sound (Cohen et al 2006). The right brain is visual and holistic. Recall is almost always visually triggered so visual representation act as a trigger for memory this creates whole brain learning (Petty 2009). 5mins Pupils answer a numeracy question on bacteria reproduction which will address numeracy on the white boards. Numeracy question on written on the white board. Teacher circle the room as pupils work to assess learning. Pupil s answers are observed and answers to the questions are received from the pupils. The correct answer to the numeracy question is worked out on the white board.

6 Development goal conception Development misconceptions Through pictures, demonstration and numeracy the spread of bacteria through asexual reproductions will be observed. Students will see how bacteria reproduce asexually. The implications for humans and bacteria of mutations, bacteria spread and antibiotics will be observed. All diseases are caused by bacteria. A mutation modifies an individual s own form during its life rather than only its germ cells and offspring. Student may believe that sexual reproduction is the only form of reproduction that can occur. 5mins Pupils will observe a practical demonstration by the teacher on how to streak the agar plates with bacteria from swabbed areas. A power point presentation with graphic organiser slide on how to sample the environment for bacteria and how to grow them on agar dishes will be observed by pupils. Teacher will give a demonstration of how to collect and grow bacteria. Explore Pair work is used as each pupil will get more contribution time than they would experience in a larger group (Kyriacou 2007). 20mins Pupils are divided into groups of three and sample the lab environment and objects for bacteria to grow on agar. Teacher will instruct pupils to work in their groups to sample the environment. The instructions for the experiment will be displayed as a power point presentation for the duration of the lab experiment. Group work gives students the opportunity to use methods, principals and vocabulary that they are being taught. Shy students are also coaxed through group work to become involved in the group. It also involves the use of higher order mental skills (Petty 2009). 5mins Pupils clean down work surfaces with disinfectant after the experiment and explain what effect this has and why you would carry this out on surfaces that food are in contact with? Teacher asks question why pupils need to clean surfaces as assessment of learning. Teacher collects Petri dishes and prepares them for incubation.

7 Questions Why are hand sanitizers required in hospitals and public places? What are antibiotics? Why are raw and cooked foods not stored together? Questions asked to pupils to answer onto mini white boards and samples of answers are retrieved from pupils. Elaborate: Pupils use what they have learnt about bacteria and bacteria misconceptions to solve real world problems. 10mins Pupils observe the white board and PowerPoint presentation on antibiotics and stopping bacteria spread. PowerPoint presentation on antibiotics and stopping bacteria spread given to pupils. Pupils are given the start and end of two different definitions about bacteria. A pupil who has the beginning of a sentence will call it out. The pupil with the correct answer will then call out their answer and call out the beginning of the next definition. pupils take part in the loop game in turn until all sentences are matched up. Each pupil is handed out a part of a sentence for a loop game. Games can create a strong participation and a quality of concentration that no other type of teaching can produce. It also increases interest and motivation towards the subject and teacher (Petty 2009).

8 5mins Analogy using power point observed on how bacteria turn harmful, a comparison to trees in a forest. Question Why would this analogy be true of bacteria? In what situations would bacteria be harmful but not harmful in other situations? Explanations of why bacteria can sometimes in certain circumstances infect humans e.g. low immunity Analogy See power point. (We don t see trees as harmful normally. A tree can kill a person; Bacteria are just like trees they are only harmful to humans in certain circumstances). Evaluate Students learning of the subject matter and correction of misconceptions can be assessed by carrying out the game and questions on the analogy. 5mins Pupils listen to a brief recap of the lesson. Teacher gives a brief recap of the lesson. Pupils take down question from the white board. How could the spread of bacteria be reduced in the school? Homework given to pupils Application of a new topic is required to be able to successfully understand it as part of Blooms taxonomy (Petty 2009).

9 Science questions What food products require bacteria to aid in their production? Are bacteria harmful or beneficial? Why are hand sanitisers required in hospitals and public places? Why do some foods have a best before date and others have a use by date? How are bacteria passed between people? What are antibiotics? What roles do bacteria play in nature? Questions during activity Name some diseases that you can think of and whether you think you can get them more than once? What is a vaccination? What vaccinations are available? What is immunity? What are pro biotics and where are you likely to find them? Why is it very important to clean a wound or a cut very well? Are viruses and bacteria the same or different? Do antibiotics work on the flu virus? Why? Do bacteria live in the digestive system? What is e coli? Meta cognition How would you promote good hygiene practice among students/ hospitals/hotels? How do you think resistant strains of bacteria come about? Any solution to stopping this occurring?

10 Loop game Bacteria are surrounded by a cell... membrane outside of which is a strong cell wall. The cell wall is made of... sugars and protein called peptidoglycan. Bacteria are said to be prokaryotic... which means that they do not have a nucleus. Round, rods and spirals... are the three shape types of bacteria. Bacteria reproduce through a method called binary... fission which means that their offspring are genetically identical. Bacteria can evolve very quickly due to... mutations within can be passed on to new bacteria. Some bacteria can withstand unfavourable conditions... by producing an endospore to protect them in unfavourable conditions. Antibiotics are compounds produced by microorganisms... that stop the growth of or kill other microorganisms without damaging human tissue. In recent times bacterial strains have emerged that are resistant to almost all known antibiotics...

11 these bacteria are said to be multi resistant. Bacterial nutrition can be heterotrophic (take in food) by feeding as... a parasite (feeding from a live host), or saprophytic (feeding from a dead source). Bacterial nutrition can be autotrophic (make their own food) by... photosynthetic (use light as an energy source to make food) or chemosynthetic (use chemical reactions as an energy source to make food). Plasmids contain... genes that are responsible for bacteria resistance to antibiotics. Low temperature slow down the rate of... bacterial growth high temperature will denature most bacteria. Most bacteria are aerobic... which means they require oxygen for respiration. Bacteria such as e coli can respire with or without oxygen... this type of bacteria is said to be a facultative anaerobe Some bacteria can tolerate very low or very high ph values... but most bacteria grow at or near neutral ph, unsuitable ph will denature the bacterias enzymes. Bacteria gain or loose water through osmosis... which is the movement of a water from a region of high to low concentration across a semi permeable membrane. Water moves out of the bacteria s cytoplasm if the external solution has a higher solute concentration than the bacteria s cytoplasm... This dehydrates the bacteria and stops their enzymes working. Salting and sugaring are used to preserve some types of meat and jams... this is an example of increasing external solute concentration to dehydrate bacteria.

12 References Atkinson,R. (2014) Forest wildlife [online], available: [accessed 20/5/14]. Carleton, J. (2014) Quest : The Science of Sustainability [online],available: [accessed 20/5/14]. Cohen, L., Manion,L. and Morrison, K. (1996) A Guide To Teaching Practice. London: Routledge. Creasey,C. (2014) Concept Cartoons [online], available: [accessed 20/4/14]. Heywood, S. (2007) A Tree Falls [online], available: [accessed 20/5/14]. Kyriacou, C. (2009) Effective Teaching in Schools. 3 rd edition., London: Nelson Thornes Ltd. Kyriacou, C. (2007) Essential teaching skills. 3 rd edition., United Kingdom: Nelson Thornes Ltd. Petty, G. (2009) Teaching Today A Practical Guide. United Kingdom: Nelson Thornes Ltd. Professional Development Service for teachers. (2014) Graphic organisers [online], available: [accessed 20/4/14]. Project Ed (2013) We Take Bacteria Misconceptions To The Street [Video online], available: [accessed 20/5/14]. Missouri Department of Elementary and Secondary Education (2005) Misconceptions in Science [online], available: accessed [20/4/14]. Todar, K. (2012) Online textbook of bacteriology [online], available: [accessed 20/5/14]. University of Sydney (2003) Gastroenteritis [online], available: [accessed 20/5/14].

13 Wikipedia (2014) Food spoilage, available: [accessed 20/5/14]. Project Ed (2013) We Take Bacteria Misconceptions To The Street [Video online], available: [accessed 20/5/14].