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BIO 111 General Biology Peer-Lead Team-Learning (PLTL) Workshop 1 The Methods of Science The first 90 minutes of each laboratory class meeting (in room 328 NMM) will consist of a PLTL workshop on subjects addressed in the lecture part of the course. These sessions are a required part of the course and will be conducted by a student peer-leader. Your laboratory class will immediately follow each PLTL workshop. The PLTL workshops will start at 13:00 and late arrivals will not be permitted. Laboratory will begin promptly at 14:30. Introduction Biology is the study of life, but it is more than a collection of ideas or observations. Biology is a way of knowing, or more precisely, it is a process or method of searching for the truth. This method, the scientific method, characterizes all the sciences and differentiates science from other ways of knowing. In this workshop, you will re- familiarize yourself with the scientific methods and its application in biology. Pre-Workshop Assignment Prior to your laboratory class meeting you should complete the questions given below and bring your completed work to your laboratory class meeting. Read the first chapter in your textbook prior to this workshop meeting. Activity A. Define the following terms : Write your answers in complete sentences on a separate sheet of paper and be prepared to submit them at the workshop meeting.
- Scientific (empirical) Question
- Data
- Experiment
- Scientific Theory
- Hypothetico-deductive method
- Independent Variable
- Dependent Variable
- Control Variable
- Deductive Reasoning
BIO 111 General Biology
- Prediction
- Hypothesis
- Experimental Group
- Control Group
- Null Hypothesis
- Observation Activity B. Questions, Hypotheses, and Predictions Scientific investigations have their origins in direct observations of living things or in reading the reports on the work of other scientists. These activities lead to questions that suggest additional investigation. Tentative answers to a scientific question are call hypotheses. Hypotheses naturally lead to testable predictions. Predictions follow from hypotheses and indicate the outcome expected in an investigation if a particular hypothesis were true. Predictions can be formulated as if … then statements. Consider the following example: In temperate environments, autumn is a time of decreasing temperatures and day-length decreases. During this time, the leaves of some trees change color and later fall from the tree (deciduous leaves). One could ask: Q: Are seasonal changes in the environment responsible for causes leaves to be shed? Tentative answers to this question would lead to one or more hypotheses: H 1 : the decline in average daily temperature causes leaves to change color and be shed H 2 : the decline in day length causes leaves to change color and be shed H 3 : the combination of temperature and day length decreases causes leaves to change color and be shed Can you think of any additional hypotheses? _________________________________
A null hypothesis (H 0 ) is the hypothesis of no relationship between the factors being considered. What is the null hypothesis for the example above? __________________
One prediction that follows from the hypotheses above is: P 1 : If H 1 (decline in daily temperature) is the actual cause for leaf color change, then exposing deciduous plants to decreased temperatures during a period of several weeks while keeping day length constant should result in leaf color changes.
BIO 111 General Biology Activity D. Controls A control is any means used to eliminate or minimize factors that might confound or obscure the relationship between the independent and dependent variable in a scientific investigation. One example of a control was described in the previous paragraph, but every good experiment has many controls in it. Consider the following: A microbiologist wants to investigate whether there is a relationship between antibiotic resistance and the antibiotics in animal feeds. She hypothesizes that antibiotic resistance increases in animals given antibiotics in their food. Specifically, she predicts that “ If animals have increasing levels of antibiotics in their feed, then there will be an increase in antibiotic resistant bacteria.” The dependent variable, the number of antibiotic resistant bacteria, can be measured in several ways. For example, the microbiologist could determine the different number of species of antibiotic resistant bacteria or estimate the number of resistant cells in a population within one species. In conducting an experiment, the amount of antibiotics put in the animal feed (independent variable) is varied systematically. All other potential variables, such as species and breed of experimental animals, type of food, housing, water quality, and environmental temperature must be standardized. If they are not controlled, these variables may influence the outcome of the experiment and confound the relationship between the independent and dependent variables. The means of standardizing these variables are called controls. Check your understanding of controls by suggesting how each of the following control variables could be standardized (held constant):
- Species tested:
- Breed of species tested:
- Diet:
- Water quality:
- Temperature of living quarters:
- Space provided to each animal: Control treatment groups are used in most scientific investigations to determine what happens to the dependent variable when the independent variable is eliminated or set to a standard value. A control group in the animal feed experiment could be fed no antibiotics. If the bacteria isolated from the control group animals became more resistant, what would you conclude about the original hypothesis? _________________________ PLTL Workshop Problems Activity 1. Identifying Empirical and Non-Empirical Statements Work in groups of six as directed by your peer leader. Science is a process of knowing based on observation, measurement and testing the predictions of hypotheses. Such knowledge is called empirical and it is evidence based. Non-science disciplines may
BIO 111 General Biology involve a different way of knowing which does not require testable hypotheses and is based on opinion, values and faith. Identify each statement below as A if it is empirical or B if it is non-empirical. Give a short explanation for your answers. _____ Leonardo da Vinci is a better painter than Picasso. _____ Alcohol consumption by pregnant women causes retardation and other birth defects in babies. _____ I know there is a God. _____ The sun rises in the East every morning. _____ Four out-of-five dentists recommend Crest. _____ People born between July 23 and August 22 should be concerned about things going wrong today, however people born November 23-December 21 will have a good day. _____ Fetal tissue transplanted into the brains of patients with Parkinson’s disease causes improvement in brain function. _____ Tissues from fetuses should be used to aid Parkinson’s disease patients. _____ Tylenol is a better pain reliever than aspirin. Activity 2. Questions, Hypotheses, Variables and Predictions Work in pairs on one of the combination of variables 1-8 below as assigned by the workshop leader. Put your work on the chalkboard to share with others in the workshop. The pairs of variables in l-8 have potential relationships. For each pair of variables: a) Write a question about the relationship. b) Write two or more hypotheses to tentatively answer the questions. c) Indicate the independent variable and a range of values it could take. d) Indicate the dependent variable and a range of values it could take. e) Make a prediction about the outcome of a scientific investigation to test one of your hypotheses. Variables:
- Studying and grades
BIO 111 General Biology State the following: a) The hypothesis b) The prediction c) The independent variable d) The dependent variable e) And experiment designed to test the prediction of the hypothesis f) One or more possible control treatments g) Two or more potential control variables h) Possible methods for addressing control variables i) You tentative conclusion about the hypothesis if the prediction is correct j) Alternative hypotheses you could suggest if the prediction were found to be false
- The concentration of salts in a solution surrounding red blood cells affects the size of the cells. If the salt concentration in the solution were decreased, then the cells will swell.
- The concentration of the enzyme A is related to the rate of the chemical reaction. If you increased the amount of the enzyme, then you will increase the speed of the chemical reaction.
- The type of sugar provided to growing yeast is related to the amount of alcohol produced by the yeast. If you were to grow the yeast in different sugars, the alcohol production would vary.
- The time a bacteria culture is under UV light is related to the number of bacteria that remain alive in the culture. As one increases the exposure time to UV light, the number of living bacteria decreases. Activity 4. Design an Experiment The public is becoming more aware of bacteria in the environment. People are aware that bacteria can be transferred from the hands to food, eyes and mouth. Your company, Soaps Dot Com, wants to expand into the area of germicidal soaps for hand washing. These soaps contain various antiseptics that kill bacteria. The effectiveness of different antiseptics in soap is unknown. Your job, as a research microbiologist, is to design an experiment to test the effectiveness of three different antiseptics that may be used in future company soaps. The workshop will be divided into groups of six students. Each group will develop the best experiment to test three antiseptics in soap. Each group must complete the following: a) Establish your hypothesis(es) with dependent and independent variables.
BIO 111 General Biology b) Generate predictions for each hypothesis. c) Identify control variables and describe how you would control them. d) Outline the steps of your experimental procedure. e) Describe your control treatment(s). f) Indicate the measurements you will use in the experiment. g) Pick one of your predictions and assume it is supported by the data. What might those results be? Activity 5. Flow-charting the Scientific Method Do this activity as a round-robin. After each person provides an answer, other students may suggest alternative answers. A flow chart can be used to illustrate the sequence of steps in a process. For example, in workshops one process of completing activities could be diagrams as follows: Leader assigns problems teams develop solution to the problems teams explain their solution to the other workshop members listeners suggest corrections or additions Briefly describe the scientific method in the form of a flow chart (in the box on the next page) using the following terms: prediction, observations, experiment, hypothesis, question, control group. experimental group, independent variable, dependent variable, controlled variable, data, theory, law.
BIO 111 General Biology Activity 7. Getting to the Truth the Scientific Way Pairs or small groups of students complete these activities and share their thinking with the other members of the workshop. A philosopher once correctly stated that scientific knowledge is “what’s left after you have demonstrated what cannot be true.” Explain what is meant by this statement considering what you know about the scientific method and how “hypotheses” become “theories”. Is there a difference between trying to verify an hypothesis as opposed to trying to falsify an hypothesis? Explain.
BIO 111 General Biology Post-Workshop Assignments If possible, work with other students so you may choose one or two of these for practice. Then show your work to your study partners and get their feedback and you can respond to the work they have done. Design a controlled experiment to test any one of the following: The effect of: a) Age of Morehouse students on grade point average b) Low dose radiation on development of human fetuses c) Height of candidate on political success in the US d) Urban smog on the frequency of respiratory illnesses e) Morning classes compared to afternoon classes on student performance f) A fast food diet on the development of diabetes g) Aggressive speeding on highway fatalities This PLTL module is based on “Biology is a Science” by M. Gaines, B. Gaydos, and J. Griswold. 2003. (University of Miami, San Jose City College, and City College of New York), with modification by L. Blumer 5/2005.
