The Dynamic of Some Biological Activities with the TI-CBL System

Transcription

1 The Dynamic of Some Biological Activities with the TI-CBL System Selma Štular & Julijana Palčič Introduction In biology class, experimental work is besides field-work the most convincing teaching method. Modern technological equipment at our school (TI-92, CBL, LCD projector, PC) has given us the possibility to modernize math lessons and biological experimental work too. Besides basic biology knowledge, we wish to provide our students also with fundamental laws of life wih integrated use of chemistry, physics, computer science, mathematics etc. At their work students learn something about modern technology, various computer programmes, the use of sensors, they learn how to present and interpret results and get ideas for research work. We believe that knowledge acquired in this way is wider and more durable; it leads to new challenges and more engagement in the field. Presentation of CBL device CBL(Calculator-Based Laboratory System) is a transportable device made to collect data from real world. Using appropriate sensors linked on to CBL device, measuring of various chemical or biological variables such as temperature, intensity of light, ph, concentration of carbon dioxide, concentration of oxygen...is possible. CBL includes a microprocessor and a memory unit for collecting and temporary data keeping. It is very convenient for field work, because it uses four alcaline batteries AA type as source of voltage. The device can be used alone, although it's real power shows when it is linked interactively with CBL- CP [2]. Symbolic calculator TI-92Plus is basically meant for teaching maths. Additional computer programmes [3] and CBL widen its field of usage. TI-92Plus sends orders to CBL e.g. velocity of taking data, number of samples, calibration information... Both, TI-92 and CBL are transportable computers linked together. CBL-CP can also be linked with PC to keep experimentally obtained data permanently. Transfer of data is carried out with computer programme TI-Graph Link 92 Plus[4]. The aim of investigation: respiration Respiration can be defined as a process that liberates chemical energy when organic molecules are oxidised. Energetically rich organic compounds are being decomposed step-by-step into carbon dioxide, water and energy in ATP (adenosine-triphosfate) form in enzyme controlled reactions.this process is carried out in every living cell [6]. Our instruments measure concentration of eliminated carbon dioxide that defines the rate of respiraton. We decided to monitor the process dynamics using special sensor linked with CBL-CP (TI-92Plus). 1

2 We investigated the respiration proces on different organisms such as yeast, insects and soya bean seeds during germination. Monitoring the respiration dynamic of yeast Yeast (Saccharomyces sp.) is a single celled fungus reproducting by cell budding. Sometimes a cell produces several buds at once or a bud starts budding before it has broken off [1]. In laboratory culture optimal conditions ( food, temperature, oxygen), budding is a very fast process. Population of cells groves exponentially that meens that population duplicates in one hour. Our yeast solution is closed system. Organisms have various sugars as a food source. They have ability to metabolise them aerobically to carbon dioxide, water and ATP which is used for their further growth. By using the CBL device we can directly monitor the respiration dynamic via the carbon dioxide concentraton released. Yeast is able to metabolise some foods, but not others. In order for an organism to make use of a potential source of food, it must be capable of transporting the food into its cells. It must also have the proper enzymes for breaking the food chemical bonds in a useful way [5]. We choose two sugars: fructose and sucrose as an energy source that we tested. We were wondering which one is better for yeast as a food. 1. Frctose 2. Sucrose Table 1.Carbon dioxide vs. time for two sugars (1.Fructose, 2.Sucrose). From the values on Table 1, we can see that yeast cannot utilise both sugars equally although the values are similar. Maybe the difference depend on different enzymes capability fot theese sugars. Students are founded out (Table 1,2), that yeast is the more active by adding sucrose as a source of food. And this is the point that is familiar to every one during bread-making or in beer fermenting in a brewery. 2

3 Diagram 1. Rate of respiration of two sugars (F-Fructose; S-Sucrose). Monitoring the respiration dynamic of insects For this experiment we chose a mealworm (Tenebrio molitor) from the fam.tenebrioide. It is a common species, often cultivated in the school vivarium. In the nature they live on trees or as terrestrial detritivores. Their larvae are feeding on decomposing wood. We can find them all over the world. They are very common in bakeries, mills and cereals warehouse as undesired guest. In our vivarium we are cultivating all three personal stages of this insects (larvae, pupae, imago). Larvae Pupae Imago Gas exchange in insects occurs via a system of pipes called the tracheal system. This allows gaseous oxygen to diffuse from the outside air directly to the tissues withaut the need for blood transmission. This is much faster than the diffusion of dissolved oxygen through the tissues and permits a high metabolic rate. We aspected the highest rate of respiration in adult stage and the lowest in the stage of pupae. Diagram 2. Rate of respiration of mealworm (Tenebrio molitor). (L-larvae; P-pupae; I-imago) We were monitoring the proces of respiration for 30 minutes. We can concluse that these insects have a very good respiration efficiency. Maybe the larval lower values of carbon dioxide expired is the consequence of the low level of ventilation movements by the body, because they were resting in our test chamber. The pupae stage does not show obvious signs of life processes. Monitoring the respiration dynamic of green soya bean seeds A typical seed stores carbohydrates, lipids and proteins in the cotyledons of an the embryo. Soya bean (Glycine max) seeds are especially rich in proteins too. 3

4 The process of germination starts with imbibition and osmosis. The embryo becomes hydrated, this activates enzymes such as the enzymes of respiration. Other enzymes have to be synthesized using amino acids provided by the digestion of stored proteins [6]. Germinated seeds obtain the energy for their activities from respiration. This involves oxidation of a substrate, usually sugar, to carbon dioxide and water. Putting the released energy (ATP) aside the other two products represent a net loss in dry mass of the seed until the seedling produces green leaves and starts to make its own food. We measured the released carbon dioxide as an indicator of the rate of respiration during the first days of germination. Diagram 2. Respiration dynamic of soya bean seeds during germination (0-nongerminated seeds; 1- first day; 2- second day; 3-trird day of germination) The respiration process of soya bean seeds is most intensive during the first and second day of germination and then decreases. CONCLUSIONS As we are beginners in the use of modern technologies, a lot of time has been spent to become familiar with the devices and their suitability for experiments. Namely sensors are very specific and sensitive. The experiments that have been realized till now will serve as a basis for internal instructions for experimental learning. Advantages of applying the computer in biology laboratory work: students' motivation increases verification of the experiment and preparing presentation of results teacher acting as advisor and giving directions more individual work and more demonstrations learning by experience (more skill using computer, graphic presentation of results..) students can compare their results to those given in instructions interdisciplinary linkage (mathematics-computer science-biology-chemistry) 4

5 Literature [1] ROBERTS, Michael: The living world, Nelson, 1991 (p , 210). [2] Vernier Software & Technology : CBL made easy, 1998 [3] [4] [5] HOLMAN, Scott, MASTERMAN, David: Biology with CBL, Vernier Software,1998 [6] GREEN, N.P.O., STOUT, G.W., TAYLOR, D.J. Biological Science, Cambridge University Press, 1994 Authors Mrs Darja Silan,M.A., biologist is currently working on the project of introducing an interdisciplinary approach to learning about natural phenomena. She would like to improve and update some practical aspects of teaching biology. Selma Štular, teacher of mathematics and computer science at Gimnazija Jožeta Plečnika Ljubljana, has been introducing computers to math classes, is involved in Comenius Project - Use Of New Technologies Within Teaching Mathematics. Julijana Palčič, teacher of mathematics at Gimnazija Jožeta Plečnika Ljubljana has been introducing computers to math classes since 1992 and has led courses for permanent professional training of math teachers about using modern technologies in math classes. She has taken part in everal international conferences on teaching math with technology. She is coordinator of Comenius project and involved in projects such as Ro with Slovene education institute and T^3 (Teachers Teaching with Technology). 5