Experimentation A.P. Biology

Observation QuestionHypothesisAndPrediction Design the Experiment Collect Data AndAnalyzeConclusion Theory BackgroundResearch SpecificInformedAnswerable Include Control Groups Control all Variables Repeat Hypothesis: What you think the answer to the question Is based on background knowledge There may be many possible answers so it is the one you want to pursue first because you think it is most likely Prediction: What you will see in the experiment if the hypothesis is true Conclusion: What you think the answer is based on your controlled, repeatable experiment When you write a conclusion: a.Summarize the data b.Tell the readers what it means (make an inference) c.Tell the reader why it is important or what is the next step to pursue – where it is going Theory: What you think the answer is Based on multiple experiments

Experimental Design Independent variable – what is being manipulated by the experimenter – it effects the dependent variable Dependent variable – what is being measured – it is effected by the independent variable Controlled variables – anything beside the IV that could effect the results (DV) – they are controlled because they must be kept the same throughout the experiment ** Control group – even though you try to control all of the variables except the IV – you may not think of one. You must always accept the possibility that there is something you didn’t think of. The control group is a test group that does not include the independent variable; therefore, if the IV is actually causing the change, then there should be no change in the control group. The CG ensures that the conclusion drawn is due only to the IV and not something you haven’t thought of. For a test – you need both a positive and negative control *** - See test vs. experiment slide

Controlled Variables Cont. ** If you can’t start with the same thing (i.e. can’t usually get people that are all eating the same and have the same lifestyle), then measure before and after and compare them to themselves There is always variability in biological organisms, therefore you will not get the exact same results even if everything is controlled – the more variability, the more repeats to make sure what you are seeing is real There is always variability in biological organisms, therefore you will not get the exact same results even if everything is controlled – the more variability, the more repeats to make sure what you are seeing is real

Experiment vs. Test Experiment – you manipulate the IV to see what happens to the DV Test – see if something is present or how much is present (do potatoes have starch? Did the driver crashed into the tree have alcohol in his system? How much protein does the brain contain? –The IV is what you are testing and the DV is the result

Practice You want to know if a certain food contains starch. You will test by adding Lugol’s Iodine which is gold. The positive test will turn the solution black You want to measure the affects of different amounts of oxygen on the rate of yeast growth by cell division You hypothesize that a certain area of the brain is important to memory. You will test this by removing this part of the brain from the rats and test the affects on their memory. You want to test the effectiveness of an anti- cholesterol drug.