COMPUTERISED LABORATORY IN SCIENCE AND TECHNOLOGY TEACHING: THE COURSE ON BIOLOGICAL PROCESSES ANDREJ ŠORGO Prva gimnazija Maribor, Maribor, SLOVENIA. E-mail:
[email protected] ALGIS DAKTARIUNAS, KASTYTIS BEITAS AND VIDMANTAS SAKALAUSKAS Dept. Biochemistry and Biophysics, Vilnius University, Ciurlionio 21, Vilnius, LT2009, LITHUANIA. E-mail:
[email protected],
[email protected],
[email protected] The specificity of biological objects determines the laboratory classes organization and requirements for computerised laboratory equipment. (1) Biological objects and processes usually are very variable, so statistical reliability of the data must be ensured by parallel measuring of parameters of set of biological objects. (2) The processes in biological systems are fast or slow ones. Usually laboratory classes last one or two academic hours. This period is sufficient to perform shortterm biological experiments, but insufficient for long-term experiments that continues for days, weeks or sometimes months. Classes must be organized in a special way in this case. Computer-based laboratory equipment (computer, data acquisition card and appropriate sensors) can measure one or many biological objects in week- or month-length experiments. The long-term continuous experiments with photosynthesis, respiration of the plants, circadian rhythms, fermentation of sugars, growth of yeast, changes in the polluted environment become more easy and usable in school or university classes. A computer-based laboratory for biology and biophysics teaching in high schools and universities is proposed in this paper. Specific requirements to data acquisition and control apparatus and software and different techniques used in laboratory works of biology are analyzed.
1
Introduction
Observation, measurement and experiment are laboratory methods used in teaching in everyday school or university practice. A work in laboratory in biology learning is important because it helps students to understand biological concepts and to get insight into scientific methods of work and reasoning. School experiments usually are much lower in level than experiments in professional laboratories. Secondary schools laboratories (and sometimes in university student laboratories) usually are more similar to laboratories of "steam machine age". It is hard to imagine the work in scientific or industrial research laboratories without computers. But often the school or university curriculum does not reflect importance of computers in real life. Many university and secondary school teachers understand phrase "use computer" as "use computer for e-mail or Internet, for a database or as sophisticated typewriter or calculator". But nowadays computers and digital systems are used in industry and medicine, in transport and at home as regulators, data-loggers, analytical tools, etc. Students must learn about sensors, data acquisition and control methods, digital signal processing. An introduction of computer-based laboratory to school or university laboratories adds new dimensions of knowledge and skills. Even the use of single computer can add new extent to teaching [5]. Another issue is a pedagogical and didactic value of computerised laboratory for biology teaching. Taylor [6] proposed the threefold taxonomy of computer use in teaching (tutor, tool and tutee) as a framework for all possible applications in education. In a biological laboratory computer is used in most cases as a tutor and a tool. Computer-based laboratory with data acquisition systems is a fine example of using computer as a tool. Use of computers in biology teaching helps to improve transfer of the knowledge to the students and to teach them to use computers as a powerful tool in a science. 2
Specificity of biological experiment: requirements to apparatus and software means
Because of great variability of biological objects and processes biological experiments differs from physics, chemistry or technology experiments. Researcher can't fully define the parameters of experiment, so a number of requirements for apparatus and software means arises.
2.1
Requirements to apparatus means
Nature of biological objects and registering parameters defines requirements for apparatus used in biological experiments. We point to the following ones: 1. Electrical signals from biological objects (especially of electrophysiological origin) are low in amplitude and corrupted by noises. Amplitudes of signals from biological individuals may be very different, so the programmable amplifier for change of scale of the input signal is necessary. Noises can be removed by different means such as shielding, differential amplifiers, various filters and digital filtering procedures in data processing programme. 2. Usually the impedance of a biological object (or registration electrodes) is high and amplifiers with high input impedance (>100 MΩ) and low input capacity are used. Additionally schemes for capacity compensation can be implemented for registration of fast transient signals (neuronal level). In experiments with biological objects sometimes it is necessary to compensate voltage level, so feedback through digital-analogue converter is useful. 3. Often the variability of individual parameters of biological objects must be evaluated. In this case biological experiment must be repeated with a number of individuals of the same species. The experiment with parallel measurement of different individuals is preferable because in this case the total time of experiment is a few times shorter. The statistical processing of data for statistical reliability is necessary in both cases (parallel or sequential). 4. Processes in biological object may be fast or slow, so it is necessary to have various sampling frequency of the signal. Computerized equipment collects data in a buffer and later transfers them to hard disk and to display for preview in experiments with the fast processes. In experiments where a few input channels are used speed of data registration is decreased. Other problem is characteristic for registration of slow processes where data acquisition and process control must be made a few times per day. In this case data acquisition system must have elements that wake up sleeping computer or interrupt the working computer each time, when data acquisition or control procedure must be executed. Another possible solution is to use autonomous (portable) data acquisition device which communicate with the host computer periodically. In experiments we used two models of devices for data acquisition and control; CMC-S2A [1, 2] and the card designed in Vilnius University [7]. Second modification of device is more applicable for biological experiments because it includes differential amplifier, programmable gain amplifier and programmable timers but in any case both apparatus successfully can be used in laboratory classes. If these functions are not implemented are needed additional amplifiers and other devices. Vernier's sensors [4] (pH, temperature, pressure, CO2) and sensors of other producers (electrodes for potential registration of the cell, temperature sensors, accelerometers, and etc.) were used in experiments 2.2
Requirements to software
Specificity of object introduces requirements to programs used in experiments of biology. Because of differences in object processes rate (fast or slow processes) we need possibility to change sampling frequency in wide interval. In fast experiments the sampling frequency must be high and data during the experiment must be writing into the buffer. The content of buffer is written into the hard disk and is displayed in a graphic form after measurement is finished. When speed of data acquisition is less than maximal data transfer speed to computer, the experiment data are displayed in real time. Problems arise for very low sampling frequencies (1 point per minute, per hour or per day), because additional control and indication of a status of the apparatus is necessary. In user interfaces such approaches are applied: 1. Manual control interface. A tool (oscilloscope, generator, digital device etc) is used with manual control of experiment parameters. Programs could be implemented by students and teachers with full control of hardware and full understanding of its work. 2. Scenario interface. Selecting of scenario name in menu automatically sets necessary parameters of experiment and the sensors. This approach is useful for laboratory works in secondary school. 3. Modular interface. An experiment is programmed by selecting functional modules according apparatus possibilities, setting specific parameters of each module and links between modules. This approach is useful for students of universities and teachers, which need to create own experiment.
Most often are programs which implement the computerised tool, but some companies of laboratory hardware and software uses an approach of modular programming. We have used the programs that implement computerised tools controlled by information from scenario files.
Figure 1. Multifunction data acquisition and control device, which realizes some requirements for experiments with biological object (differential inputs, high input impedance, programmable gain amplifier). Experiment is controlled by program that uses the tools for registration and generating of digital signals
3
Experiments and techniques of experiments
Biological experiments in schools can be classified to two groups: a) experiments on human (usually physiological experiments – electrocardiogram, myogram, audiogram registering; tremor, skin conductivity, breath frequency, air flow speed, force measurements etc); b) experiments on plants, fungi, prokaryotes and animals (respiration rate; photosensitivity, electric cell potentials, pollutants influence, growth rate, etc). School biology experiments can be of various fields, for example: a) human psychophysiology (colour vision, reaction time, recognition time , etc); b) behavioral biology (rat's orienting in maze, fishes movement in aquarium,); c) ecology (electrical potentials of algal cells and bivalve mollusks opening frequency in clean and polluted water; radiant heat accumulation in hill slopes etc); d) simulation (model for colour vision, model for measuring a pressure of the blood, etc); Usually experiments on human physiology and psychophysiology and simulation experiments are short-term experiments. And, for example, in direct opposition are some experiments on environment pollution or on physiology of plants that are long-term ones. 3.1
Short term experiment
The short-term experiments can be defined as experiments that are shorter than one or two academic periods. The greatest benefit of computerised experiment is automatic data gathering and simultaneous graphical presentation of them on a computer screen. Possibility of digital data analysis is another benefit in complicated experiments. So attention of the students can be directed to the experiment. Because students get the results in graphical and numerical form immediately so they can start discussion on the progress of experiment immediately. The statistical data analysis can be used in such experiments (in university laboratories such analysis is a must). The third merit of computerized experiment is possibility to control experiment. Students can immediately amend errors in execution of experiment. An example of typical short-term experiment data is shown in figure 2. In this example the data acquisition and digital processing were made using different programs. We suppose that scientific data in university teaching laboratories must be analysed by programs (for example, Microcal Origin [3]) that can process very long data records that usually are characteristic for short-term experiments.
Figure 2. Experimental curves of the heart rate of the human. The second curve had been obtained by applying digital filter to data of original signal. Additional external amplifiers haven't been used, gain – 1000, time interval between samples 10 msec.
3.2
Long term experiment
The long-term experiments can be defined as experiments that are longer than one or two academic periods. Many processes in living systems take much longer time. Some biological experiments are relatively boring because changes can not be detected for hours or even for days. Examples include fermentation of sugars or the growth of bacterial cultures. In a laboratory without a computer-based data acquisition system the students would have to take data every hour or other times period what is completely impractical. It is also impossible to register manually data at night or at weekend in the school. The use of paper-based self-recorders brings up other problems – the special self-recorders are necessary for different experiments and there is problem of data transfer from paper form to electronic form. Use of computer changes this. Long-term experiments are set up in the presence of the class, preferably a day before holidays or the weekend. Results are collected by selected students at the first working day. Students get copied data sheets or graphs of continuing experiment. These copies are used as starting points for a discussion at the following lessons. Special case is when many groups of students must execute the same
Figure 3. Screenshot of graph obtained in three days experiment where photosynthesis rate in aquarium were indirectly measured. The dependence of light intensity and concentration of dissolved oxygen is clearly visible.
experiment with limited laboratory capacities. The multiplicity of experiments is solved through results sharing. The experiment is started with every class but finished with the last group only. After completion of the entire experiment all the students in each class get copies of the graphs and data. An example of long term experiment results is shown in figure 3. 4
Discussion
Laboratories for biology studies in secondary schools and universities require very expensive equipment with specific parameters and complicated data analysis systems. There is only one way to solve that problem – to use a computer-based laboratory which includes suitable data acquisition and control devices, various sensors and software for data registration, processing and analysis and for simulation of biological processes. Use of the computers in a biological laboratory has several aspects: a) a computer-based laboratory allows to implement many experiments that were implemented in special scientific laboratories; b) a computer-based laboratory allows demonstration or performance of many experiments in a new way preferred by most students; c) students are learning that computers are powerful scientific tool for data collecting, processing, analysis, interpretation and presentation; d) possibility to collect a data both in long-term or very short-term experiments; e) possibility to automate an experiment of data gathering and generation of stimulus; f) software or hardware simulations are a means for students to perform experiments virtually when real experiments are too expensive or too dangerous to be performed in a school or university;
g) simulation gives a possibility to study conditions that are outside of our experimental abilities. 5
Acknowledgements
This work is supported by European Commission, project "Leonardo da Vinci", the grant SI14008. 6
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