Student Background: The Scientific Method
Biology is defined as the study of living things. Without even taking a biology class, most people can very easily define whether something is living or not. Your textbook? Not living. Your pet hamster? Living. Biology is easy! Living things share common characteristics, for example, living things acquire and use materials for energy, living things grow and reproduce, and living things respond to stimuli and maintain relatively constant internal conditions. Living things will meet all the specified criteria; therefore it is relatively easy to classify something as living or non-living. Remember that biology is the study of living things, it’s a process. One of the great things about being a scientist is that science is something you do, not something you only read or hear about. In this way, science is a verb!
How do biologists study life? Biologists notice phenomena about the living things around them and then examine them. There are many types of biologists. Some biologists study the whole living organism, while others study life at its smallest unit; the cell. Regardless of whether the biologist is studying the predatory behavior of the arctic fox or the regulation of cell communication in cardiac cells, there is a systematic method for exploring the phenomena of life. Biologists, like other scientists follow the Scientific Method. The Scientific Method is a five step process that guides the scientist. The five steps are:
1) Determine the problem/make an observation: This is the question you have about why something is the way it is or how it works. For example, “Why does the fur of Himalayan rabbits turn white in the winter?” Your observation is that Himalayan rabbits do turn white in winter, the problem is why?
2) Formulate a hypothesis: A hypothesis is an educated guess that explains the problem. For the problem above, your hypothesis may be that Himalayan rabbits turn white in winter to blend into the snowy environment so they won’t get eaten!
3) Experiment: Experiments must be carried out to confirm or deny your hypothesis. Experiments may involve manipulation of the natural environment or not. Many scientists purposefully change a factor to see what effects it might have. For example, a scientist might change the salinity of the water in a fish tank to determine its effects on the aquatic life in the tank. On the other hand, a phenomenon can also be studied without manipulation. If the phenomenon is observed and the observations recorded systematically, this is still considered an experiment even though nothing was manipulated. For example, many animal behaviorists study their chosen subjects in the field in the natural environment of the subject. The animals are not manipulated; the natural behavior is simply observed and recorded. Remember that not all science experiments take place in a lab!
4) Recording your data: What did you find out from your experiment? Data are all the things you found out from your experiment. How many white rabbits survived until spring? How many brown rabbits survived? How many fish survived the change in salinity in the tank?
5) Drawing conclusions: Interpret your results. Do they confirm or deny your original hypothesis? It is okay if your hypothesis turned out to be “wrong,” maybe you found out that the rate of Himalayan rabbits getting eaten as prey had nothing to do with their fur color! That would mean your hypothesis was “wrong,” but it also means that there is some other reason that their fur turns white in winter. Sometimes negative data (when your hypothesis is wrong) gives just as much information as when you’re right. In either case, the experiment contributed information about the problem. One of the wonderful things about science is that whenever a conclusion is reached, it usually has led to another question!
Experimental Design
One of the most important steps of the Scientific Method is the design of the experiment. The best experiments are the most simple and examine only one variable at a time. Let’s say you wake up the morning of prom with a huge pimple on your face! You panic and call all your friends to find out what to do. Each one has a different remedy for your problem. You don’t know what to do so you do everything every friend has said. Hours later, you’ve applied Windex, Clearasil, half a lemon and toothpaste to the pesky pimple, and it has disappeared! You conquered the pimple, but next time, you won’t really know which remedy worked because you applied them all! In a real scientific experiment, you would test one variable at a time, and try to control for all the other variables. Did your pimple disappear because of all the treatments or would it have vanished on its own? We don’t know because we didn’t use a control in this experiment (of course you’d never experiment with pimples at prom!).
What exactly are variables and controls? The variable is what is being tested. In the above experiment, the treatment for the pimple is the variable. A scientist wants to limit the number of variables in an experiment as much as possible. You would not put all the treatments on the pimple at the same time, that’s too many variables! It is easy to manage the number of variables you are testing in a laboratory environment by changing only ONE thing at a time. But, sometimes it is not so easy, and some variables are harder to control. Two pimples on two different people might behave differently. Two pimples that popped out on different days might behave differently. No two pimples are exactly alike and you can’t control for that variability. Obviously the same person with two pimples that showed up on the same place of the face on the same day would be great, but sometimes the scientist can’t manage all the variables. The best you can do is limit the variables to ensure that only the variable being tested will affect the result. To do this, having proper controls in place during an experiment is crucial.
Controls make certain that the result has only to do with the variable being tested and not some other circumstance in the experiment. A negative control should do nothing. A pimple that is not treated (a negative control) should NOT go away. If the untreated pimple and the treated pimple both clear up, you can’t really say the treatment did any good. A result that is ascertained alongside a negative control can be believed. For example, a pimple that is treated goes away while the untreated one stays in place. Now we can say that the treatment affected the pimple and not something else. A positive control shows what should happen. For example, if the experiment is trying to show that toothpaste can clear up a pimple as fast and as effectively as a dermatologist’s expensive prescription medication, the positive control is the expensive medicine and the variable is the toothpaste. Controls are in place to allow the scientist a comparison with the variable being tested.
Let’s think about that pesky pimple again in terms of experimental design. Let’s say that instead of waking up with one pimple, you wake up with two. A true scientist would leave one pimple alone with no treatment (the control) and would treat the other pimple with only one remedy, the toothpaste (the variable). After time, data can be recorded; what is the status of the pimples? If both pimples are gone, clearly the treatment was not responsible as the control pimple disappeared as well. If only the treated pimple is gone, then we can deduce that the toothpaste treatment cleared up the blemish. If both pimples are still there, we can deduce that the toothpaste treatment is a dud. This is a well-designed (albeit risky) pimple experiment. Even though you might still have a pimple at prom, you know what type of treatment works! Furthermore, you can tell a friend in the same predicament exactly what to do if they run into the same problem!
Scientific experiments must produce reproducible data. That is, if you conduct an experiment and get a particular result, another scientist should be able to perform the same experiment and get the same results. That is why it is important to document your experiment from start to finish. Most scientists do this by keeping a laboratory notebook.
Keeping a Laboratory Notebook
In research labs, laboratory notebooks are considered legal documents. They can be used to prove that that a particular scientist came up with a specific idea or product before anyone else did. In this case, the scientist would use the laboratory notebook to help secure a patent on the idea or product. Lab notebooks can also be examined by the FDA (Food and Drug Administration) or the EPA (Environmental Protection Agency) when they are trying to approve a new drug. When used in a real research lab, laboratory notebooks belong to the company or educational institution that employs the scientist. Of course your laboratory notebook will be owned by you. Although lab notebooks are considered legal documents, their overall importance lies in what is written inside them! Inside a laboratory notebook, a scientist will write how to carry out an experiment. Essentially, there will be a “recipe” for how to carry out an experiment, and notes on any changes that were made during the experiment. Results are also recorded in the laboratory notebook. All the information on how the results were procured should be in the notebook so that another scientist could repeat the experiment in their own laboratory and get the same results. The basic guidelines for keeping a lab notebook are:
Ø A lab notebook is kept in chronological order with each page dated in long hand, i.e. June 23, 2009 instead of 6/23/09.
Ø Use a bound notebook, not a notebook where pages could be removed.
Ø Label the front of the book with your name, the name of your institution (school) and the dates that the notebook covers (i.e. Fall semester 2010)
Ø Number every page and do NOT rip out pages.
Ø Use pen and write down everything into the notebook, even things that seem trivial go into the notebook. Don’t write things down on napkins or scraps of paper. Keep your notebook with you and write in it!
Ø Write legibly and don’t erase errors, instead cross them out with a single line.
When you enter an experiment into your notebook, write the procedure into the notebook, or cut and paste it into your notebook. This will include the amounts of all the reagents that you use (i.e. 500 ml H20 or 50 g NaCl), the more detail you can provide, the better your laboratory notebook will be. Even if it seems obvious, you should write it down! When recording results, write down exactly what happened, not what you hoped would happen; the more details, the better. You can add drawings if it helps. Check out this link http://www.loc.gov/exhibits/treasures/trr002.html to scroll through Alexander Graham Bell’s notebook on the invention of the telephone!
Interpreting results
Oftentimes carrying out an experiment is the easiest part of science. Interpreting results can be trickier. Scientists often try to get quantitative data, i.e. numbers. During the design of an experiment, think about how your results will look. If we go back to those Himalayan rabbits, you see that you want to measure the number of rabbits that are white vs. the number that are not. You measure the numbers that are eaten vs. the number that are not. That way your data is quantitative and you can do things with those numbers. For example, you can determine percentages. “80% of white rabbits survived the winter and were not eaten by predators vs. 30% of brown rabbits.” “Three times more white rabbits survived than brown rabbits.” This type of data is quantitative and objective. It is important that your results be objective vs. subjective. The results are the raw data, and NOT your opinion.
The Scientific MethodPage 4 of 4 / Contextual Biology Integrated Projects
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