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Richardson%20Scientific%20Method - BIOLOGY A LABORATORY...

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Unformatted text preview: BIOLOGY: A LABORATORY GUIDE TO THE NATURAL WORLD Second Edition Dennis I. Richardson and Kristen E. Richardson Quinnipiac University ' PEARSON A Prentice Hall Upper Saddle River, N].:07458 KrogLChflle.qxd refs/0'4 1:09 PM Page 1 Way of Learning Science as a We start oficonficsed and end up confused on a higher level. Here you are, in a biology course that you’ve put off as long as possible. Does the word science give you an uneasy feeling? Science can be overwhelm- ingly complex, but learning about it doesn’t have to be. A famous scientist once said that science is “nothing but trained and organized common sense” (Huxley, 1854). Take it one step at a time, and you will see how the pieces fit together. Start by observing something about the liv- ing world around you. You may notice a vine-like morning glory climbing on a fence, for example (Figure 1.1).Then ask a question.Why do the flow— ers of a morning glory bloom (open) only for a few hours each day? By asking a question, you are al- ready on your way to understanding biology. You may not realize how many steps you take just to ask a question: you look at the plant on several oc- casions, and you observe how the flowers are open in the morning, but closed later in the day. Why do they bloom only for a few hours? The steps you take to answer the question will flow in a logical manner. You think of some factors that may affect blooming. Do the flowers open only on sunny days? Does blooming depend on the temperature? Does humidity play a part in blooming? You decide to answor your question by investigating one of the possibilities. If blooming is temperature-dependent, then the flowers should FIGURE 1.1 Morning Glory. mete AE. Chalmers, 1976 KrogLChDJV2.qxd 2/6/04 1:09 PM Page 2 2 Biology: A Laboratory Guide to the Natural World open as the temperature climbs and close as high- er temperature approaches. After observing the flowers for a few days, you may see a pattern that is consistent with the temperature—dependent approach. Or you may see a pattern that isn’t. In either case, you could start the investigation over to learn additional informa- tion. If the flowers bloom in a temperature-depen- dent manner, you can investigate why they might do so. Or if temperature doesn’t seem to have an effect or: blooming, you can eliminate that possi- bility and investigate another. In this manner, we do indeed start off con- fused (with a question} and end up confused (with another question) on a higher level! Much of bio]— ogy is discovered with this approach, called the scientific method [Krogh section 1.2]. As you can see, it is only organized common sense, but it can lead to fascinating knowledge. rI‘HE SCIENTIFIC METHOD How do we know what we know? The study of the acquisition of knowledge is called epistemology— the very root of our methods of learning. Four major intellectual endeavors have been pursued by human cultures throughout history—religion, philosophy, art, and science. Let's examine how science differs from these other three intellectual pursuits. Religion is defined as the service and wor— ship of God or the supernatural; it is a commitment or a devotion to religion or faith. Philosophy is the pursuit of wisdom; a search for a general understanding of values and reality by chiefly speculative rather than observational means; an analysis of the concepts expressing fun- damental beliefs. Art is the conscious use of skill and creative imagination, particularly regarding aesthetic ob jects. Aesthetics is a branch of philosophy dealing with the nature of beauty, the quality in something that gives pleasure to the senses or pleasurably ex- alts the mind or spirit. Science is knowledge covering natural phe- nomena or the operation of general laws as obtained and tested through the scientific method. Science differs from the other three intellec- tual pursuits in that it is grounded in ompin'cism (study of phenomena that can be seen or mea~ sured), whereas the other three tend to be more a abstract or subjective. This fundamental difference does not make science better than religion, art, or philosophy. On the contrary, it could be argued that this difference places extreme limitations upon science, because none of the others have em- pirically defined boundaries. Yet, empiricism gives great strength to science, because it enables hy- potheses to be tested objectively. The morning glory example presented in the introduction fits into the steps of the scientific method. 1 Observation You observe that morning glory blooms only during certain hours of the day. In many experiments, this step includes per- sonal observation as well as reading what is already published. Such pieces of informa- tion are sometimes referred to as facts. In science, a fact refers to a piece of informa- tion; this is unlike the vernacular (everyday) use, where fact refers to a statement of truth, or something that is undeniable. . 2 Question The question that follows is, Why do the blooms close at midday? _ 3 _ Hypothesis A hypothesis is a tentative, gen- eral statement based on specific observa- tions. You have several hypotheses: Sunlight afiects blooming. Temperature afifects bloom— ing. Humidity affects blooming. 4 Prediction Predictions are logical conclu- sions to be expected in view of the hypothe- sis. They may be phrased in the form of an if-then statement: If the hypothesis is cor- rect, then a certain outcome is expected. Predictions provide opportunities to find in- dependent pieces of evidence supporting a hypothesis, as well as opportunities to reject a faulty hypothesis. From the temperature hypothesis, this prediction follows: If bloom- ing is temperature—dependent, then the flow» ers should open as the temperature climbs and close as higher temperature approaches. Experiments Predictions are tested by obser- vation and/or experimentation. If you con- duct your experiment over a few days, you may find that blooming is temperature-de- pendent. Or you may not. 6 Conclusion New data are the product of ob— servation and experimentation. The new data will either support or fail to support the hypoth- esis. (Datum is singular, and data is plural). U! 4% HogLChOlv2.qxd 2/6/04 1:09 PM Page. 3 A hypothesis can never be proven. To claim that you have proven a hypothesis is to claim that you have a hold on absolute truth. Within the con- ceptual boundaries of science. absolute truth is unat- tainable. This is not to say that absolute truth does not exist, just that it can never be known in regard to science. It is most appropriate for a scientist to use terms like data rather than facts and principles rather than truths. It is better for a scientist to say that data suggest than to say that data prove something. Why is a scientific discovery not “absolute truth?” There are several reasons. One is because hypotheses are based on observations and data from a particular point in time. We are continuous- ly learning more about the world around us, and, sometimes, new information pushes old conclu- sions aside. You may say “Eureka! 1 have proven that blooming in morning glories is temperature— dependcnt!” But you’ll be scratching your head if someone else finds that the flowers bloom even in colder (yet very sunny) weather next week. And so, you’ll have to show your objectivity, step aside, and consider their findings. Once a hypothesis has amassed a great amount of supporting evidence, it may be afforded the status of theory. A theory is a general set of principles that explain some aspect of nature. Note that a theory is not a hypothesis that has been proven. It is a hypothesis with a tremendous amount of supporting evidence. In scientific use. a theory is a widely accepted paradigm. or model, that is supported by a tremen- dous amount of evidence. In vernacular use, theory refers to an idea, often with no more validity than a guess. Exercise 1.1 EXPERIMENTAL DESIGN In designing an experiment, several variables are defined: The independent variable is the variable that is manipulated. You manipulate the tempera- ture of the plant's atmosphere. The dependent variable is the variable that will be measured. You measure plant blooming, noticing the temperature at which the plant blooms. Controlled variables are kept constant throughout the experiment. The soil type, Chapter 1 Science as a Way of Learning 3 amount of water applied, and amount of light are kept constant. The experimental group contains plants that are subjected to manipulation. Morning glory plants in this group will be subjected to rising temperature. The control group cuntains plants held under standard conditions, in which the independent variable is not manipulated.'Ihe control group usually approximates “normal” conditions. However, these plants should be grown in the lab to eliminate effects of humidity and plant growth, variables we do not want to test in this experiment. Morning glory plants in this group will be exposed to constant temperature. Read this very carefully: When comparing the experimental group to the control group. the effects of the independent variable can be deter— mined by measuring the dependent variable in both groups. You compare blooming in the experi- mental group to blooming in the control group. Does temperature appear to have an. efl’cct on blooming? lfyes, then the data support the hypoth- esis. If no, then the hypothesis is rejected. When scientists compare experimental groups to control groups, they do so using statistical analyses, which are mathematical tests to determine whether observed differences in the two groups are “real” or are a result of “pure chance.” When a sci- entist claims that something is significantly different from something else, she is implying that the differ- ences are real according to statistical analysis. After reading the Big Red Fertilizer exam- ple, identify the components of its experimental design in the following questions: Farmer Hen read an article in Sodbuster magazine that some researchers “dewn at the U" had developed a new fertilizer called Big Red Fertil- izer.’1"he product was supposed to be nothing short of an agricultural miracle. It produced corn plants that had more cars per plant. The article even claimed that kids who ate the com grown with Big Red Fertilizer would turn into star athletes On the basis of what he read and what he had heard, Farmer Hen generated the hypothesis that Big Red Fertilizer enhances corn production better than regular fertilizer. From this hypothesis, Farmer Hen predicted that if Big Red Fertilizer enhances corn production better than regular fertilizer; then a KrogLChclv2.qxd 2/6/04 1:09 PM Page4 $ 4 Biology: A Laboratory Guide to the Natural World com plants raised on Big Red Fertilizer will have 4. Which plants are included in the control more ears of com per plan! than corn raised on reg- group? ular fertilizer. He designed an experiment to test the prediction as follows: Corn was planted at the same time in two adjacent fields. One field was fertilized with Big Red Fertilizer and the other received regu- lar fertilizer. The fields were plowed on the same days and were irrigated, receiving equal amounts of water on the same days. At the end of the season, Farmer Hen ob- served the corn plants and found that plants main- 5. Identify the independent variable. tained on Big Red Fertilizer indeed had more ears than those that had received regular fertilizer. Thus his prediction was found to be correct, and the hypothesis that Big Red Fertilizer enhances corn production better than regular fertilizer was supported. Note that although the hypothesis was supported, it was not proven to be correct! Questions - 6. Identify the dependent variable. 1. What is the hypothesis? 7. Identify the controlled variables. 2. What is the prediction? 8. What conclusion would be drawn if the corn plants in the control field were found to have more ears of corn per plant than plants from the experimental field? 3. Which plants are included in the experimen- tal group? ...
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