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Lab 1 Biology: Exploring Life Antibiotics Too Much of a Good Thing? Antibiotics Your doctor prescribes an antibiotic and specifically cautions you to take every pill. Why? Antibiotics Checkpoint What is an antibiotic? a. It is a toxin used by bacteria to kill molds. b. It is a drug that can kill infectious bacteria. c. It is a chemical produced by the body to defend itself against viruses. d. It’s an area with conditions that don’t support life. e. None of the above are correct. Antibiotics Checkpoint Human white blood cells ________. a. carry oxygen and carbon dioxide to the lungs b. store antibiotics for release at sites of infection c. serve as one of the body’s natural lines of defense against microbial invaders d. gather and eliminate antibiotics from the site of an infection e. All of these are correct. Antibiotics Checkpoint About half of the antibiotics produced today __________. a. end up in animal feed b.are used by field hospitals in war zones c. are shipped to third-world countries d.become useless due to developing resistance by bacterial populations e. are stored for later use Antibiotics Checkpoint How do bacteria populations become drug resistant? a. Antibiotics remove drug-susceptible individuals but leave those that are drug-resistant. b. Natural selection drives bacterial populations to change. c. Some individuals are genetically resistant to antibiotics. d. All of these are correct. Antibiotics Checkpoint Which of these is not an effective strategy to prevent antibiotic resistance? a. Don’t stockpile antibiotics. b. Don’t demand antibiotics from your physician. c. Use antibiotics only as long as symptoms remain. d. Use antibiotics as prescribed. e. Don’t share antibiotics with others. Antibiotics Biology and Society The development of antibiotic resistance by bacteria illustrates how natural selection affects our lives. Can you name another way our society experiences the effects of natural selection? Antibiotics Biology and Society Discussion Question The development of antibiotic resistance by bacteria illustrates how natural selection affects our lives. Can you name another way our society experiences the effects of natural selection? Follow-Up Questions • Is it likely that insect or plant pests (weeds) might develop resistance to pesticides and herbicides? • Some plants, like BT corn and BT cotton, are being engineered to include a pesticide gene. What do you predict to be the long-term success of such a strategy? What strategies should a farmer employ to prevent pests from becoming resistant? Antibiotic resistance in bacteria is not the only case in which humans are causing pressures that contribute to the natural selection of a population. Other examples include insect resistance to BT corn, BT cotton, and other natural and genetically altered crops (http://www.nature.com/nsu/021202/021202-2.html). A great deal of research is being conducted to develop strategies to prevent pest populations from developing pesticide resistance (http://www.biotech-info.net/ECB.pdf). Antibiotics Biology and Society Many antibiotics—like penicillin—are no longer effective, but it is costly to develop replacements. Do we have an obligation to societies that cannot afford to develop these new and expensive antibiotics? Antibiotics Biology and Society About 50% of the antibiotics produced today are used in the livestock industry. What impact does this have on the treatment of human diseases? Antibiotics Internet Research Antibacterial Soap Doesn’t Prevent Viral Infection (http://kidshealth.org/research/antibacterial_products.html) This article outlines our use and misunderstanding of antibacterial soaps. Are there concerns that bacteria will develop resistance to antibacterial soaps? Drug Companies Snub Antibiotics (http://www.nature.com/nsu/030915/030915-6.html) The article speculates that drug companies are spending less money and less effort to develop new antibiotics. What evidence does the author cite? What are the consequences to global health if this is the case? Is Your Meat Safe? (http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/) This site outlines the debate over the use of antibiotics in the livestock industry. Familiarize yourself with the issues, then share your thoughts (http://www.pbs.org/wgbh/pages/frontline/shows/meat/talk/). Was the coverage fair and unbiased? Antibiotics Summary • We didn’t have antibiotics before the 1940s. • Alexander Fleming helped to develop the first antibiotic from a mold. • Antibiotics work to kill infecting bacteria. • Natural variations exist within bacterial populations that make some bacteria resistant to antibiotics. • Abuse of antibiotics promotes the development of antibiotic-resistant bacteria. Antibiotics Preventing the development of antibiotic-resistant bacteria is in the hands of every individual. What actions will you take? Five Steps of the scientific method 1. Observation come from others or results of earlier tests 2. Questions are asked about unclear aspects of the observations: How? Why? When? 3. Hypotheses are tentative explanation of a phenomenon phrased in such a way as to be testable. 4. Predictions are logical, testable outcomes of the hypotheses developed by the use of deductive reasoning. Predictions take the form of if (statement of hypotheses) is true, then (predictions). 5. Tests of prediction are performed to determine if the predictions are supported (fail to falsify) or falsified. Concept Check Not all science discoveries strictly follow the “scientific method”. Which of the following would best be described as discovery science? • Sequencing the human genome. • Describing a new bird species from the Philippines. • A project to find preserved specimens of the probably extinct Rocky Mountain locust frozen in glaciers . • All of the above. Answer Not all science discoveries strictly follow the “scientific method”. Which of the following would best be described as discovery science? • All of the above. A Case Study of Hypothesis-Based Science • In experiments designed to test hypotheses – The use of control groups and experimental groups helps to control variables Figure 1.8B Figure 1.8C Percent of total attacks on artificial snakes 100 80 84% 83% Artificial brown snakes 60 40 20 0 17% Coral snakes absent Figure 1.8E Figure 1.8D Artificial king snakes 16% Coral snakes present Interpreting Data These two snakes look remarkably similar to each other. The coral snake (right) is very poisonous to vertebrates. Hypotheses: H1: The coral snake’s bright color pattern serves to warn off potential predators. H2: The the king snake suffers less predation because it mimics or looks like the coral snake. H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes. Interpreting Data A team of scientists designed an investigation that used artificial snakes to test the previous hypotheses. Which of the previous hypotheses are supported by the results displayed at the right? • H1: The coral snake’s bright color pattern serves to warn off potential predators. • H2: The the king snake suffers less predation because it mimics or looks like the coral snake. • H3: The protection that king snakes receive by mimicking coral snake will depend on the presence of coral snakes. • Both A and B Answer A team of scientists designed an investigation that used artificial snakes to test the previous hypotheses. Which of the previous hypotheses are supported by the results displayed at the right? • Both A and B Interpreting Data Biologists placed artificial snake mimics in two different localities to test the hypothesis that looking like a poisonous snake only works where the poisonous snake is found: 1. Outside of the coral snake range—only king snakes present. 2. Inside the coral snake range— both coral and king snakes are present. Interpreting Data The data graphed at the right __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is: • supports • does not support • is irrelevant to Answer The data graphed at the right __________ the hypothesis that the effectiveness of mimic coloration depends upon the presence of the poisonous model is: • supports Interpreting Data Based on this data which of the following is a logical hypothesis or prediction? • King snakes outside of the range of coral snakes will more closely resemble coral snakes than populations of king snake living within the range of coral . • King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes. • Neither prediction is valid. Answer Based on this data which of the following is a logical hypothesis or prediction? •King snakes outside of the range of coral snakes will not resemble coral snakes as closely as populations of king snakes that live within the range coral snakes. Controls •This case study provides an example of a controlled experiment, one that is designed to compare an experimental group (the artificial king snakes, in this case study) with a control group (the artificial brown snakes). •Ideally, the experimental and control groups differ only in the one factor the experiment is designed to test–in our example, the effect of the snakes’ coloration on the behavior of predators. Controls •Without the control group, the researchers would not have been able to rule out the number of predators in the different test areas as the cause of the different number of attacks on the artificial king snakes. •The clever experimental design left coloration as the only factor that could account for the low predation rate on the artificial king snakes placed within the range of coral snakes. Hypothesis Theory needing investigation: a tentative explanation for a phenomenon, used as a basis for further investigation The hypothesis of the big bang is one way to explain the beginning of the universe. Hypothesis - defined A conjecture advanced for heuristic purposes, cast in a form that is amenable to confirmation or refutation by conducting of definable experiments and the critical assembly of empiric data; not to be confused with assumption, postulation, or unfocused speculation. Heuristic: LOGIC procedure for getting solution: a helpful procedure for arriving at a solution but not necessarily a proof Deduction •Conclusion drawn: a conclusion drawn from available information. •Drawing a conclusion: the process of drawing a conclusion from available information. •LOGIC logical conclusion: a conclusion reached by applying the rules of logic to a premise. •LOGIC reasoning: the forming of conclusions by applying the rules of logic to a premise A Case Study from Everyday Life • Deductive reasoning is used in testing hypotheses as follows – If a hypothesis is correct, and we test it, then we can expect a particular outcome Two important qualities of the hypotheses-based science 1. A hypothesis must be testable. 2. A hypothesis must be falsifiable. A hypothesis becomes credible when repeated attempts to disprove it fail. Introduction to Lab 1 • scientific inquiry is a particular way of answering questions • questions that can be answered by science must meet specific guidelines and scientific investigations must be carried out using certain rules • an investigator cannot show that his or her experiment was done according to the guidelines, then the results of that experiment will not be recognized as valid by other scientists Introduction to Lab 1 • The purpose of such guidelines can be understood by comparing them to sports records. For example, a new record set in a track and field event only counts if the meet was approved by the governing body that sets the guidelines. The site and equipment used are scrutinized to be sure that they are within the regulations and the athlete is tested for use of illicit substances. Only when these required conditions are met is the record certified as valid. Introduction to Lab 1 • In this laboratory you will learn about the basic elements of scientific inquiry and how to apply this process to solving problems. Exercise 1.3: The Elements of an Experiment Objectives: 1. Define and give examples of dependent, independent, and standardized variables. 2. Identify the variables in an experiment. 3. Explain what control treatments are and why they are used. 4. Explain what replication is and why it is important. Exercise 1.3: The Elements of an Experiment • Variables are things that may be expected to change during the course of the experiment. •The investigator deliberately changes the independent variable •He measures the dependent variable to learn the effect of changing the independent variable. •To eliminate the effect of anything else that might influence the dependent variable, the investigator tries to keep standardized variables constant. Dependent Variables The dependent variable is what the investigator measures (or counts or records). It is what the investigator thinks will vary during the experiment. For example, she may want to study peanut growth. One possible dependent variable is the height of the peanut plants. Name some other aspects of peanut growth that can be measured. Number of peanuts, weight of the plants, leaf area, time to maturation. All of these aspects of peanut growth can be measured and can be used as dependent variables in an experiment. There are different dependent variables possible for any experiment. The investigator can choose the one she thinks is most important, or she can choose to measure more than one dependent variable. Independent Variables The independent variable is what the investigator deliberately varies during the experiment. It is chosen because the investigator thinks it will affect the dependent variable. Name some factors that might affect the number of peanuts produced by peanut plants. Amount of fertilizer, type of fertilizer, temperature, amount of water, day length, genetic type of the peanuts. Standardized Variables • A third type of variable is the standardized variable. Standardized variables are factors that are kept equal in all treatments, so that any changes in the dependent variable can be attributed to the changes the investigator made in the independent variable. Standardized Variables • Since the investigator's purpose is to study the effect of one particular independent variable, she must try to eliminate the possibility that other variables are influencing the outcome. • This is accomplished by keeping the other variables at constant levels, in other words, by standardizing these variables. Standardized Variables •For example, if the scientist has chosen the amount of fertilizer as the independent variable, she wants to be sure that there are no differences in the type of fertilizer used. She would use the same formulation and same brand of fertilizer throughout the experiment. What other variables would have to be standardized in this experiment? Amount of water, temperature, day length, genetic type of peanuts. Predictions • A hypothesis is a formal, testable statement • The investigator devises an experiment or collects data that could prove the hypothesis false • He should also think through the possible outcomes of the experiment and make predictions about the effect of the independent variable on the dependent variable in each situation. • It is useful to think of a prediction as an if/then statement: If the hypothesis is supported, then the results will be ... Levels of Treatment • Once the investigator has decided what the independent variable for an experiment should be, he must also determine how to change or vary the independent variable. • The values set for the independent variable are called the levels of treatment. Control Treatments • It is also necessary to include control treatments in an experiment. •A control treatment is a treatment in which the independent variable is either eliminated or is set at a standard value. •The results of the control treatment are compared to the results of the experimental treatments Control Treatments 1. An investigator studies the amount of alcohol produced by yeast when it is incubated with different types of sugars. Control treatment: A treatment with no sugar. 2. The effect of light intensity on photosynthesis is measured by collect ing oxygen produced by a plant. Control treatment: Put a plant in the dark. 3. The effect of NutraSweet sweetener on tumor development in laboratory rats is investigated. Control treatment: One group of rats receives no NutraSweet sweetener. 4. Subjects are given squares of paper to taste that have been soaked in a bitter-tasting chemical. The investigator records whether each person can taste the chemical. Control treatment: Use some papers that do not contain the chemical. 5. A solution is made up to simulate stomach acid at pH 2. Maalox antacid is added to the solution in small amounts, and the pH is measured after each addition. Control treatment: Add water instead of Maalox antacid. Replication •Replicating the experiment means that the scientist repeats the experiment numerous times using exactly the same conditions to see if the results are consistent. •A concept related to replication is sample size. •It is risky to draw conclusions based upon too few samples. Methods investigator must find a method to measure the dependent variable; otherwise, there is no experiment. investigator must find a method to measure the dependent variable; otherwise, there is no experiment.