General Biology 1, Lecture 3 notes
General Biology 1, Lecture 3 notes 101-NYA-05
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This 4 page Class Notes was uploaded by CatLover44 on Monday September 5, 2016. The Class Notes belongs to 101-NYA-05 at Dawson Community College taught by Virginia Hock in Fall 2016. Since its upload, it has received 6 views. For similar materials see General Biology 1 in Biology at Dawson Community College.
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Date Created: 09/05/16
General Biology 1 Course Number: 101-NYA-05 Lecture no. 3 Date: Wednesday, August 31, 2016 Professor: Dr. Virginia Hock Topics Covered: the scientific method, experimental and control groups, independent, dependant, and control variables, avoiding biases during data collection, the importance of result replication and sample size. The Scientific Method • Results obtained from a scientific experiment are procured from observations or experiments. If the results from an experiment are accurate, other scientists should be able to replicate them. • Scientific findings should not depend on the reputation of the experimenter, or to support a favourable outcome. • There are two main types of scientific experiments: 1) Discovery scientific experiments, which entail watching natural phenomena without altering them in any way. Qualitative data is obtained from these types of experiments. 2) Hypothesis-based experiments, which entail explaining nature by manipulating natural phenomena using experimental procedures and control parameters. o Most scientific experiments combine discovery and hypothesis-based experimentation. Ordered Steps of the Scientific Method Step 1. Make an observation about a natural occurrence that scientists would want to explain. Research the work of other scientists that was done on the phenomenon you observe. Step 2. Ask yourself questions about what you notice from your observations. Step 3. Form a hypothesis (a falsifiable statement). Step 4. Predict what types of results you will likely obtain from your experiment (based on your hypothesis). Step 5. Test your predictions: (a) Plan what types of experiments you'll conduct, and what your controls will be; (b) Perform your experiments; (c) Collect data and analyze it. Step 6. Interpret your data: does it support or fail to support your hypothesis? Step 7. Draw conclusions. For example, if you turn on a flashlight and it doesn't work, you usually do two things: you make an observation (Step 1: observe the flashlight isn't working) and you ask yourself why it isn't working (Step 2: ask yourself questions about your observation). Maybe your hypothesis (Step 3) would be that the batteries are dead, so you predict that changing its batteries will fix the issue (Step 4). However, when you change the batteries, the flashlight still won't work (Step 5). The results of the experiment don't support your hypothesis (Step 6), so you must draw another conclusion (Step 7) in order to find out how to fix the flashlight. What are Hypotheses? • Scientific inquiry requires proposing and testing hypotheses. o A hypothesis is an educated guess that explains a phenomenon, or answers a question. It can be based on scientific research or available data. Scientists use hypotheses to help them predict what the results of their experiments will be. o A hypothesis is a tentative explanation; it serves as a temporary explanation for some natural phenomenon. o A hypothesis is a falsifiable statement; it must be possible for someone else to prove that it is wrong. o Even if the results of your experiment support your hypothesis, this doesn't mean that your hypothesis was correct. It just means that your results supported your hypothesis. A hypothesis becomes more credible if it isn't falsified by other scientists. No amount of experimental testing can prove a hypothesis. For instance, in the flashlight example, even if changing the bulb fixed the problem, we still don't know for sure that a defective bulb was preventing the flashlight from working; maybe the last bulb was just not attached tightly enough. Proper Experimental Design • When conducting a scientific experiment, experimental groups and control groups are used so that the results of the experiment in each group can be compared to each other. • All the procedures you do to the experimental group should be done to the control group, except for the one procedure that is used to test your hypothesis. All other conditions must be the same in order for your results to be valid. o For example, consider the hypothesis that removing a nucleus from a cell will cause it to die. The experimental group would consist of several cells, all of which 2 will have their nuclei removed. The control group will have the same environmental settings as the experimental group (same temperature as in the experimental group, experiment done at the same time as it was for the experimental group, using cells of the same size, etc.) except their nuclei will only be touched by a probe instead of removed. This is done to make sure that the cell wouldn't die just by being touched by a probe. • Scientific experiments hold great biological importance because they can explain the reasons behind certain physical mutations. o An experiment was done in order to discovery why Pacific tree frogs grow extra legs. Due to this experiment, scientists discovered that, when the Pacific tree frogs eat these parasites (called ribeiroia), they develop extra limbs. Theories & Hypotheses • If a hypothesis is credible, it may become a theory. o Theories are different from hypotheses because they are recognized as a viable explanation for a set of hypotheses, whereas a hypothesis is an educated guess. Proper Experimental Design • Variables are the parts of a scientific experiment which may or not be controlled. Scientific experiments may have different amounts or types of variables. o Independent variables are those that are manipulated by the experimenter. o Dependent variables are obtained through changes to the independent variable. They're also referred to as the output or response. The experimenter has no control over the dependent variables. o Control variables are the factors of the experiment that are kept the same between the experimental and control groups. o The control group is the group that does not receive the main treatment that's provided to the experimental group. All the other experimental conditions are the same between both groups. The results obtained from this group are compared to the results obtained from the experimental group. • Use proper scientific methods when conducting your experiments in order to avoid biases, which impact the validity of your results. o The experiment must be repeated in order to ensure accurate results. • Biases occur when extraneous factors affect the data you're collecting. o For example, if someone volunteers for an experiment and they think that taking a certain drug will improve their mood, they may actually end up feeling more cheerful through no fault of the medication provided to them as part of the experiment. This is called the placebo effect. 3 o Double-blind experiments are experiments where the experimental group and the control group are not told whether they are going to receive the placebo or the actual treatment. These experiments reduce the chances of obtaining biased results. o Use large sample sizes and several replicates to get dependable data from your experiment. • Using a sufficient sample size allows us to draw more accurate conclusions from the data procured from an experiment. Repeating the experiment several times also yields the same result: data that is credible. • Practicing ethics is of utmost importance while conducting scientific experiments. Always be kind to animals, and respectfully to volunteers that offer their time to further your research. Remember to avoid outbreaks if working with viruses. • You can't change data once you've obtained it. 4
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