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The Scientist's Purpose

11/6/2013

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Scientists change and shape our world by developing explanations and making sense of the things we do not know or do not understand in our world (and outside of our world).  For example, Louis Pasteur's controlled experiment that investigated the question, "Can microorganisms (germs) generate spontaneously?" has completely changed modern medicine.  Pasteur proved that microorganisms do not grow randomly, and that microorganisms must travel through the air or through direct physical contact in order to grow.  

As result of Pasteur's experiment, billions and billions of lives have been saved.  For hundreds of years now, doctors around the world make sure to wash their hands and sanitize facilities to keep disease-causing germs from spreading.  In our school, we know always to wash our hands before and after experimenting, and to cover our mouths when sneezing.  We have Louis Pasteur to thank!

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As we move forward with selecting our testable questions for our independent scientific investigations, it is important that we think about the purpose and meaning of our investigations.  Not every science experiment can (or should) totally change something as dramatic as the way we practice medicine, but every science experiment should aim to shed some light on something that is meaningful to someone out there.  That someone may be you, a family member, friend, pet, or all of the above!  Just remember to think about how answering your testable question (through a controlled experiment) can make some sort of impact.  

Scientists are problem solvers.  They observe problems in our world ("O" in Dr. OPHERC), such as the increase in greenhouse gases in our atmosphere, the spread of malaria, the rise of diabetes in the United States, the shortage of drinkable water in certain parts of the world, species extinction, etc.  With these observations, scientists develop purpose/questions ("P" in Dr. OPHERC) that are testable for investigation to gather evidence to shed light on why these problems exist and how to solve them.  

Our experiments may not shed light on something as "big" as global warming, but will definitely give you a better understanding of something that is important to YOU or someone in your life.  This understanding can lead you (and possibly others) to make better decisions.  These decisions can be related to health (how to snack more healthfully), academics (how to study more effectively), performance in sports (how to score more points in a soccer game), and even performance in video games (so that you have more time to do your homework, of course)!

If you find that none of the testable questions you have developed (so far) have any meaning or purpose (to you), don't be afraid to start from scratch.  Just make sure to start with a topic that is interesting and/or meaningful to YOU.

Will YOU be the next Louis Pasteur?!  
In-Class Assignment
Answer the questions below in your science notebook.  Write the question and answer in COMPLETE sentences.

1.  How did Louis Pasteur's experiment change/shape our world?

2.  Pick the testable question (among those you have written) that means the most to you.  What is the purpose of this testable question?  

3.  WHO could benefit from the information you gather through your scientific investigation? 

4.  HOW might those individuals benefit from the information you gather through your scientific investigation?

5.  What materials will you need to conduct the experiment (include people, place, and things)?

6.  Identify the variables in your experiment:
     IV: __________________________________________________________
     DV: _________________________________________________________
     C: __________________________________________________________
     CG: _________________________________________________________

7.  What materials will you need to measure your dependent variable?

8.  What might be difficult about conducting your experiment/collecting data?

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Controlled Experiments

10/22/2013

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What is a controlled experiment?

A controlled experiment is an experiment that is conducted under a setting that is “controlled” by the scientist with the least possible influence from outside factors.  A controlled experiment compares an experimental group with a control group in the exact same conditions with the one exception of a special/different treatment given to the experimental group. 

The control group represents the "normal", "standard" or untreated condition.  The experimental group is the one part of the experiment that is changed/manipulated (given different treatment).  The constants are everything else you keep the same to ensure a fair test.

Francesco Redi's Controlled Experiment: Do maggots (young flies) come from rotting meat?

To better understand controlled experiments, let's look at Francesco Redi's famous controlled experiment on maggots and meat as an example.  Francesco wanted to find the answer to the question, "Do maggots (flies) come from rotting meat?".  This may seem like a really silly question, but in Francesco Redi's day (1600s), people actually believed that flies and maggots were generated spontaneously from meat.   Take a look at Redi's experiment below.
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What conditions did Francesco keep the same?  What was the one special/different treatment given to the meat?  
Louis Pasteur's Controlled Experiment: Can microorganisms (germs) generate spontaneously?

Louis Pasteur also conducted a famous controlled experiment.  His experiment addressed the question, "Can microorganisms (germs) generate spontaneously?"  For hundreds of years before Louis Pasteur, scientists believed that microorganisms (living things too small to see with the naked eye) came from thin air.  Below is Pasteur's experiment.
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What conditions did Pasteur keep the same?  What was the one special/different treatment given to the flasks?  
A controlled experiment is a "fair" test
A controlled experiment is usually the fairest and most accurate way for a scientist to gather evidence to test a claim (hypothesis). Therefore, we will be using controlled experiments, like Francesco Redi and Louis Pasteur, in science class this year as we develop scientific explanations of phenomena that interest us.

A controlled experiment can be replicated
Another important thing to note about controlled experiments is that they are super easy to replicate (copy).  Therefore, any scientist should be able to gather the same evidence and results when conducting the same experiment.  In other words, if you performed Francesco Redi's famous experiment from the 17th century today, you would get the exact same results (replicated results)!


Limitations of a controlled experiment
However, keep in mind that controlled experiments have their limitations.  First of all, not every experiment can be controlled in a laboratory setting.  For example, if you want to study things in nature, such as how specific plants and animals interact in the rain forest, there are many factors that you would not (and should not) be able to control/change.  Furthermore, controlled experiments do not necessarily represent real-world conditions, and can therefore create unrealistic results.  For example, if a scientist is able to prove the effectiveness of a new drug (medicine) in a controlled laboratory setting, this does not necessarily mean that the drug will be as effective among people who have very different diets and live in very different environments.
In-Class Activity

Perform Redi and Pasteur's famous controlled experiments here!  Then answer the questions below. 

1.  What is a controlled experiment?

2.  What are the two "groups" in a controlled experiment?
3.  What is a control group?
4.  What are constants?
5.  Identify the experimental and control group in Francesco Redi's controlled experiment.
6.  How was Louis Pasteur able to gather evidence to prove that microorganisms do not generate spontaneously?  Explain.  If you need help, review Louis Pasteur's experiment here.
7.  Why do you think it is important to keep all conditions in a controlled experiment the same except the one special/different treatment?
8.  Why is it important that you can "replicate" a controlled experiment?
9.  What is one limitation of a controlled experiment?
Homework

Watch the video below on a controlled experiment studying the effect of ozone on plants  Then answer the questions in your science notebook in complete sentences.

1.  What was the question the scientists were trying to answer through this controlled experiment?
2.  How were all of the plants treated the same?
3.  What is a variable?
4.  What is the variable (one thing changed) in this experiment?
5.  What was the control/control group in this experiment?
6.  What is a control/control group?
7.  What do the scientists measure/record everyday in this experiment?
8.  Why do you think it is important that scientists only test one variable in an experiment?
Extra Credit:

Watch the video of how students set up a controlled experiment to investigate the effect of mirrors on dolphin behavior: http://vitalny.pbslearningmedia.org/resource/737ed8f2-10bb-484e-9b75-e3f19a91f3a4/dolphin-dive-05-test/
Then answer the questions below.

1.  What was the control test/group in the dolphin experiment?
2.  What was the experimental group in the dolphin experiment?
3.  How do you think the students could have improved their experiment?
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