Thus, as much as possible, you should only have one independent variable in your experiment. Additional independent variables will require more complicated procedures and data analysis, however, if one is willing to put more effort in getting conclusive results, are not prohibited. In fact, any of the controlled variables have the potential to be independent variables. Multiple independent variables, could also give data on combination effects of these variables. For example, while magnitude and length of exposure both might have separate effects on the yield of the soybean plants, they could also produce different results when their treatments are applied together. However, as stated, analysis of effects becomes complicated, requiring greater effort in part of the performers of the experiment (Palmer, M., n.d.). Some of the variables of the sample experiment on soybeans and SO2 have already been stated earlier.
1. duration of exposure; selected age of soybeans; kind of gas exposed 2. the number of seeds per pod; the weight of the pods (both after exposure to gases) 3. The different gases exposed to the set-ups. It is important to have only one independent variable in order to have consistency when testing for only one possible predicted result. 4. duration of gas exposure; age of the soybeans 5. duration of gas exposure; same age of all soybeans; same kind of fumigation chamber
Proper designing of procedures is crucial to the credibility of your workas other scientists should be able to perform your experiment and obtain your results consistently for your conclusions to be considered a worthy contribution to the body of knowledge that is science.
Count the number of seeds and total weight of podsCount the number of seeds and total weight of podsRepeat with 3 other groupsRepeat with 3 other groupsPlace one group in filtered air chamber for 4 hoursPlace one group in SO2 chamber for 4 hoursDivide into 4 groups of 6Divide into 4 groups of 6Divide into 2 groups of 24Select 48 soybeans with approx. same age
INTRODUCTION Plant Physiology study of how plant life exists requires observation, asking questions and proposing explanations Scientific Investigations -way of testing explanation about plant phenomena - similar to scientific method Plant Physiologists - ask questions, make observations, develop explanatory hypotheses and test those hypotheses
ASKING QUESTIONS Why ask? Requires well-defined and measurable phenomenon Elements must be measurable and controllable
ASKING QUESTIONS Does exposure to ultraviolet radiation cause increased risk of skin cancer? Will eating cassava cause poisoning by demons? Does good nutrition lead to increased intelligence Why do cacti have spines? Was the malignant tumor found in the lungs of a 70- year-old man caused by his 45-year habit of smoking cigarettes? Is it true that Plant Physiology students are all pretty and handsome? Does overwatering plants cause death of plants?
ASKING QUESTIONS Do plants have feelings too? Will I get a grade of 1.00 in Plant Physiology? Are all plants photosynthetic?
DEVELOPING HYPOTHESESHypothesis A tentative answer to some question An explanation on trial An educated guess (Campbell, 2004)
HYPOTHESIS Experiments are designed to falsify the hypothesis by producing evidence to disprove it. If the evidence that is gathered does support the hypothesis, the hypothesis is accepted but only on a trial basis. It is never accepted as absolute truth because future investigations may still falsify the hypothesis.
HYPOTHESIS Must be stated in a way that is can be easily measured and must be constructed in a way that will help in answering the question
B. DEVELOPING HYPOTHESISB1. Write a hypothesis for the following questions:1. Why are there so many trees in the tropical rainforests of the Philippines? -> There are many trees due to sufficient sunlight and abundant rainfall.
2. What is the function of the tendril of ampalaya? -> The tendril functions as a support for the plant as it climbs along the substrate.3. What is the effect of fertilizer on a lettuce patch? -> Fertilizer improves the growth and the productiveness on a lettuce patch.
4. How does lahar soil affect plant growth? -> Lahar soil increases plant growth.5. Why is organic fertilizer better for plants? -> Organic fertilizer provides less toxic chemicals than inorganic fertilizers.
DEVELOPING HYPOTHESISB2. Which of the following would be useful as a scientific hypothesis? If yes, give the reason by stating whether it could possibly be falsified and what factors are measurable and controllable.
1. Garlic can be used against snake bites. -> Yes. Garlic has been used through ages and is also known as remedy for snake bites. -> The biochemical composition of garlic may be studied in order to know the efficacy of the remedy on snake bites. -> The control variable would be the amount of remedy to be applied on the affected area of the body.
2. Tetanus is caused by stepping on rusty nails. -> Yes. It can be falsified by hospital records whether tetanus is only caused by rusty nails.3. Parasitic plants are evolutionarily more advanced than non-parasitic plants. -> Yes. It can be verified and better understood through plant systematics.
4. Drinking beer can improve one’s memory. -> Yes. A standard test can be given to two groups – one which will be given beer to drink and another group without beer. This set-up can be used to support or falsify the hypothesis.
5. Bio 121 students are better gardeners than non-Bio 121 students. -> No. The definition of “better gardeners” is vague. Again, the hypothesis is subjective.
DETERMINING THE VARIABLES Scientific experiment composed of variables, and a procedure to test them. Defining variables greatly dependent on the question and hypotheses formulated at the start of a scientific investigation. the goal of an experiment is to provide clear evidence to falsify or support a particular explanation.
TYPES OF VARIABLES Independent Variable one assumed to cause a particular phenomenon Dependent Variable is the effect of the said phenomenon Controlled Variable is regulated to determine if the independent variable is the true cause of a phenomenon
METHODOLOGY Identify the variables in preceding investigation. Classify whether it is independent, dependent or controlled variable. Only 1 independent variable is usually chosen Consider alternative independent variable
INVESTIGATION OF THE EFFECT OF SULFUR DIOXIDE ON SOYBEAN PRODUCTION Agricultural scientists were concerned about the effect of airpollution, sulfur dioxide in particular, on soybean production in fieldsadjacent to coal-powered power plants. Based on initialinvestigations, they proposed the sulfur dioxide in high concentrationswould reduce reproduction in soybeans. They designed anexperiment to test this hypothesis. In this experiment, 48 soybeanplants, just beginning to produce flowers, were divided into twogroups of 6. One group of 6 treated plants were placed in a fumigationchamber and exposed to 0.6 ppm of sulfur dioxide for 4 hours tostimulate sulfur dioxide emissions from a power plant. The experimentwas repeated on the remaining three treated groups. The notreatment plants were placed similarly in groups of 6 in a secondfumigation chamber and simultaneous exposed to filtered air for 4hours. Following the experiment all plants were returned to thegreenhouse. When the plants matured, the number of bean pods,number of seeds per pod and the weight of the pods were determined
Agricultural scientists were concerned about the effect of airpollution, sulfur dioxide in particular, on soybean production infields adjacent to coal-powered power plants. Based on initialinvestigations, they proposed the sulfur dioxide in highconcentrations would reduce reproduction in soybeans. Theydesigned an experiment to test this hypothesis. In this experiment,48 soybean plants, just beginning to produce flowers, were dividedinto two groups of 6. One group of 6 treated plants were placed ina fumigation chamber and exposed to 0.6ppm of sulfur dioxide for4 hours to stimulate sulfur dioxide emissions from a power plant.The experiment was repeated on the remaining three treatedgroups. The no treatment plants were placed similarly in groups of6 in a second fumigation chamber and simultaneous exposed tofiltered air for 4 hours. Following the experiment all plants werereturned to the greenhouse. When the plants matured, the numberof bean pods, number of seeds per pod and the weight of the podswere determined for each plant.
VARIABLES Duration of exposure Selected age of soybeans Kind of gas exposed Number of seeds per pod Weight of the pods
DEPENDENT VARIABLES The number of seeds per pod The weight of the pods
INDEPENDENT VARIABLE Different gases exposed to the set-ups. It is important to have only one independent variable in order to have consistency when testing for only one possible predicted result. Duration of gas exposure Age of the soybeans
CONTROLLED VARIABLE Duration of gas exposure Same age of all soybeans Same kind of fumigation chamber
CHOOSING OR DESIGNING THE PROCEDURE Once the variables have been decided upon designing of the procedure takes place. The procedure should be written in such a way as to make the experiment repeatable. Proper designing of procedures is crucial to the credibility of your work in order to perform the experiment and obtain the results consistently for the conclusions to be considered a worthy contribution to the body of knowledge that is science.
Procedure must contain all the steps that have undertaken in the experimentation, including any modifications to the original procedure, control treatments, levels of treatments and number of replications (Evangelista, 2009)
METHODOLOGY Enumerate the step by step activities of the experiment in soybean production.
Count the Place one Repeat number of group in with 3 seeds and Divide into 4 SO2 other total groups of 6 chamber groups weight of for 4 hours podsSelect 48soybeans Divide into with 2 groups approx. of 24same age Place one Count the Divide into Repeat number of group in 4 groups of with 3 seeds and filtered air 6 other total weight chamber groups of pods for 4 hours
There are two main components of the procedure: two manipulated variables (SO2 and natural air) and each component having 4 replicates.
MAKING PREDICTIONS Predictions on the phenomenon is formed in question
EXAMPLE We can predict that, after the results of the soybean experiment if ever the SO2 concentration was doubled, the decrease in the overall yield could be doubled as well. One may choose to perform another experiment based on these predictions, in order to form better conclusions about a particular phenomenon.
Thus predictions are important as they bring us closer to a better understanding of the natural world (Made Simple, Inc., n.d.).
MAKING PREDICTIONS If the hypothesis is true, the result would be the high SO2 concentrations do reduce reproduction of soybeans.
TABLESTabulation A compact and orderly manner of presenting information Can readily point out trends, comparisons or interrelationships
TABLESGuiding principles in table construction: Simplicity clean and uncluttered Directness only necessary information Clarity jive with textual discussion
TABLESEssential parts of a table: Table number Title Column headings Row headings or stubs Body with data Footnotes (if applicable) Sources of data (if applicable)
GRAPHS OR FIGURES Provide visual summary of the results
GRAPHS OR FIGURES1. Bar graph qualitative or quantitative discrete for comparisons of absolute or relative counts, rates or proportions between categories of a qualitative or a quantitative discrete variable
GRAPHS OR FIGURES2. Pie chart qualitative shows the breakdown of a group or total where the number of categories is not too many
GRAPHS OR FIGURES3. Component bar diagram qualitative same as pie chart except that it can be used to compare the breakdown of categories of more than one group
GRAPHS OR FIGURES4. Histogram quantitative continuous graphic representation of the frequency distribution of a continuous variable or measurement including age groups
GRAPHS OR FIGURES5. Frequency polygon quantitative same function as histogram
GRAPHS OR FIGURES6. Line diagram time series shows trend data or changes with time or age (x-axis) with respect to some other variable
GRAPHS OR FIGURES7. Scatterpoint/scatterplot quantitative shows correlations between two quantitative variables (whether directly or inversely related)
GRAPHS OR FIGURESIn making the graph, remember the following:a. Use graph paper and ruler to plot the values accurately
GRAPHS OR FIGURESIn making the graph, remember the following:b. The independent variable is graphed on the x axis and the dependent variable on the y axis
GRAPHS OR FIGURESIn making the graph, remember the following:c. The numerical range for each axis should be appropriate for the data being plotted
GRAPHS OR FIGURESIn making the graph, remember the following:d. Label the axes to indicate the variable and the units of measurement.
GRAPHS OR FIGURESIn making the graph, remember the following:e. Choose the type of graph that best represents your data.
QUESTIONS1. Given the following data from the soybean experiment, how do you arrange the following data (in the manual) from the experiment in a table?2. What kind of graph are you going to construct?
TABLE 1. SOYBEAN REPRODUCTION EXPERIMENT Plant No. Control Plant Treatment with SO2 No. of seeds Ave. weight of No. of seeds Ave. weight of per pod seed (g) per pod seed (g) 1 5 0.42 2 0.21 2 6 0.37 4 0.33 3 4 0.41 4 0.23 4 5 0.36 3 0.35 5 5 0.48 3 0.25 6 6 0.33 3 0.34 7 7 0.44 1 0.21 8 6 0.23 4 0.32 9 5 0.51 5 0.21 10 7 0.47 3 0.38 11 4 0.46 4 0.27
TABLE 1. SOYBEAN REPRODUCTION EXPERIMENT Plant No. Control Plant Treatment with SO2 No. of seeds Ave. weight of No. of seeds Ave. weight of per pod seed (g) per pod seed (g) 12 5 0.37 3 0.35 13 7 0.53 4 0.22 14 6 0.42 4 0.34 15 5 0.51 4 0.23 16 6 0.39 5 0.35 17 5 0.48 5 0.12 18 5 0.47 5 0.34 19 7 0.52 5 0.22 20 7 0.50 6 0.30 21 6 0.28 2 0.20 22 6 0.39 2 0.30 23 7 0.21 4 0.21 24 7 0.41 3 0.13
TABLE 2. NUMBER OF SEEDS PER POD No. of Plants No. of seeds per pod Control Treatment 1 - 1 2 - 3 3 - 6 4 2 8 5 8 5 6 7 1 7 7 -
7 6Ave. seeds per pod 5 4 3 2 1 0 Control Treatment with SO2 Treatment Figure 1. Comparison on the average number of seeds per pod between plants under control and treatment with SO2
0.45 0.4Ave. weight of seed (in grams) 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Control Treatment with SO2 Treatment Figure 2. Comparison on the average weight of seed between plants in the control and treatment with SO2
DISCUSSING AND COMMUNICATING RESULTS Provide interpretation to the results. State the interpretation’s implications in light of the hypothesis and its supporting literature.
DISCUSSING AND COMMUNICATING RESULTS Investigators study the given tables and graphs and determines if the hypothesis is supported or falsified.
DISCUSSING AND COMMUNICATING RESULTS IF FALSIFIED: Investigators must suggest other possible alternate hypotheses. IF SUPPORTED: Investigators must suggest other experiments and studies that will strengthen the current hypothesis.
DISCUSSING AND COMMUNICATING RESULTS The results must be communicated to other scientists. May be in the form of a laboratory class presentation or during scientific gatherings.
DISCUSSING AND COMMUNICATING RESULTS Most important: The study is to be presented in the form of a scientific paper or a journal after subjecting it to review by different scientists in the same field of study.
DISCUSSING AND COMMUNICATING RESULTS E1. Using your graphs and tables, analyze your results and discuss your conclusions with your group. -> 1. According to the graph of the number of seeds per pod, there is higher number of results in the controlled set-up, while the number of seeds with SO2 treatment has lower yield. As to the weight of the seeds, higher values were gathered in the control as well as lower values were gathered in the set-up with SO2 treatment. It is therefore concluded that SO2 decreased the productivity and development of the seed.
DISCUSSING AND COMMUNICATING RESULTS E2. Critique your experiment. What weaknesses do you see in the experiment? Suggest improvements. -> 2. The number of replicates is somehow too much, but still it gave a meaningful result. The results somewhat gave overlapping information and lacks some data. The range of the measurements is somehow inconsistent.
DISCUSSING AND COMMUNICATING RESULTS E3. Write a summary statement for your experiment. Use your results to support or falsify your hypothesis. -> When the plants were treated with SO2, the number of seeds per pod decreased as well as the average weights of the plants. These results supported the hypothesis which states that SO2 in high concentrations would reduce reproduction in soybeans.
DISCUSSING AND COMMUNICATING RESULTS E4. Suggest additional and modified hypotheses that might be tested. -> High concentrations of SO2 sometimes do not decrease the reproduction in soybeans; high concentrations of SO2 decrease usually the reproduction in soybeans.
CONCLUSION The essential feature of science that makes it difficult from other ways of understanding the natural world is the scientific method. The scientific method provides a step by step process of finding explanations behind the different phenomena observed in the natural world. It begins by asking a question that is well defined and testable. Also, its elements are measurable and controllable.
CONCLUSION After forming a scientific question, one can develop a hypothesis which is a possible explanation to answer the scientific question. For a hypothesis to be scientifically useful, it must be testable and falsifiable. In order to test the hypothesis, a scientific experiment must be designed. Its components are determining variables, designing procedure and making predictions.
CONCLUSION Results from the experiment must be summarized and presented in tables or figures. Also, these must be interpreted, discussed and communicated to other scientists. Hence, this step by step procedure makes certain that the knowledge obtained cannot be fabricated because a lot of processes must be undertaken before conclusion can be done.