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.

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?

Scientific Method = Gathering Evidence

Last week, we learned that the Scientific Method is an organized method used by scientists to find and gather evidence (data) to support a claim (argument) about what the scientist observes.  There are many versions of the scientific method, but all versions of the scientific method involve trying to answer a specific question, and experimenting to find the answer.

The version of the scientific method that we will use in my class was given to me by my dear friend, Dr. OPHERC:

• Observation: The observation is simply any information gathered using the senses or an instrument.  A scientific investigation begins with an interesting observation in the world that generates questions that can be tested.

• Problem/Question: The problem/question is the specific question the scientist will attempt to answer through experimentation.

• Hypothesis: The hypothesis is the claim of the scientist, or an educated guess about the answer to the problem/question.  A hypothesis is based on sufficient observations, prior knowledge, and background research.  

• Experiment: The experiment is when the scientist actually tests his/her hypothesis for supporting evidence using detailed procedures, appropriate materials, and scientific measuring tools.  During the experiment, the scientist records all of his/her qualitative and quantitative observations.

• Results: The results are all of evidence (the qualitative and quantitative observations) gathered throughout the experiment.  The results are often displayed in tables, charts, and graphs for further studying. 

• Conclusion: The conclusion is the reasoning of the scientist that explains the meaning or significance of the results.  In the conclusion, the scientist links the evidence from the experiment back to the original claim (hypothesis).     

Scientific Explanation = Goal of a Scientist

During the first week of school, we learned that science is a way to develop explanations for what we observe, using the evidence we gather through our own experiments, and through the experiments of other scientists.  A scientific explanation, so to speak, is the scientific way of explaining what we observe in the world (and outside of the world, too!).  A scientific explanation is essentially a claim (about what a scientist observes/observed phenomena) that is supported with evidence and reasoning.  
The goal of a scientist is to develop scientific explanations to share with the scientific community, and the purpose scientific method is to gather the "evidence" component of the scientific explanation.  

But what is a claim?  What is evidence?  And what is reasoning?!  These components of a scientific explanation (C.E.R.) have been outlined below.

C.E.R. = Parts of a Scientific Explanation

• Claim: a conclusion that attempts to answer/address a testable scientific question. 
• Evidence: appropriate and sufficient data from an experiment, other scientists' experiments, reading material, and/or other observations that support the claim.  
• Reasoning: a justification that links the claim and evidence that incorporates appropriate and sufficient scientific principles; requires background research.  

Connecting the Scientific Method with C.E.R.

Last week, we performed an experiment to gather evidence in order to develop a scientific explanation. The question we addressed was, "What is the most common color in a 2.17 oz Original Fruit bag of Skittles?"

Below is an outline of how we gathered our evidence via the Dr. OPHERC.  We will use class 711's data for our example.

1.  The scientific method began with an observation.

Observation: There are five different colors in a bag of skittles - red, yellow, orange, green, purple.  Every time I eat a bag of skittles, the frequency (how many) of each color seems to be different.  

2.  This observation inspired, or led to, a question for investigation.

Problem/Question: What is the most common color in a 2.17 oz "Original Fruit" bag of Skittles?  

3.  We made a tentative claim (hypothesis) to test, based on our observations, background research, and prior knowledge.

Hypothesis: If purple is the most popular color of Skittles, then it will be the most common color in a 2.17 oz bag because the makers of Skittles will likely accommodate the preference of the consumers.  Furthermore, according to Skittles.com, green should make up 19.7% of a 2.17 oz bag, yellow should make up 19.5% of a 2.17 oz bag, orange should make up 20.2% of a 2.17 oz bag, red should make up 20% of a 2.17 oz bag, and purple should make up 20.6% of a 2.17 oz bag. 

4.  We then tested our hypothesis through an experiment to gather evidence.

Experimental Procedure:
1.  Open the bag of Skittles onto your sheet of paper towel.
2.  Group your Skittles according to color. 
3.  Count how many of each color are present in your group’s bag and record this info in table 1.   
4.  Analyze your data by creating a bar graph on Table 2.
5.  Make sure to label the graph showing colors and numbers of Skittles. 
6.  Form a conclusion.  State whether your hypothesis was correct or incorrect and why. 

5.  Next, we graphed all of our data (evidence).

Results:
Average number of red (class 711): 11.5 pieces
Average number of yellow (class 711): 13.3 pieces
Average number of orange (class 711): 10.2 pieces
Average number of green (class  711): 13.5 pieces
Average number of purple (class 711): 10.2 pieces

6.  We then made a conclusion by determining whether or not the evidence gathered supported our original claim.  The conclusion is essentially our reasoning.  The conclusion addresses our original claim (was it correct?  incorrect?), provides our evidence, and links our evidence back to our original claim.

Conclusion: My hypothesis was not supported through this experiment because I predicted that purple would be the most common color, and my results show that green is the most common color in this experiment.  The average total number of candies in class 711 was 58.6 pieces.  There was an average of 10.2 red candies, 13.3 yellow candies, 10.2 orange candies, 13.5 green candies, and 10.2 purple candies in a 2.17 oz bag.  Class 711's results were different from class 711, 714, 715, and 716. My next step is to average the data from all four classes.  Since every class has a different average frequency of colors, the results do not provide enough evidence to support or oppose my claim that purple is the most common color of skittles in a 2.17 oz bag.  Furthermore, since Skittles.com states that green should make up 19.7% of a 2.17 oz bag, yellow should make up 19.5% of a 2.17 oz bag, orange should make up 20.2% of a 2.17 oz bag, red should make up 20% of a 2.17 oz bag, and purple should make up 20.6% of a 2.17 oz bag, it is important that we increase our sample size in order to have a fair test.

Homework:

Answer the following questions in your science notebook.  Write the questions AND answer in complete sentences.

1.  Why do scientists use the scientific method?
2.  What is a scientific explanation according to this article?  Cite your evidence.
3.  How is the "reasoning" in a scientific explanation related to the claim and evidence?  Explain.
4.  According to this blog post, a claim is a conclusion that attempts to answer/address a testable scientific question.  What is another way to define claim?
5.  According to this blog post, evidence is appropriate and sufficient data from an experiment, other scientists' experiments, reading material, and/or other observations that support the claim.  What is another way to define evidence?
6.  Were we able to gather enough evidence through our Skittles experiment to support a claim that a particular color is the most common in a 2.17 oz bag of "Original Fruit" Skittles? Explain.
7.  Using the scientific method does not always provide the necessary evidence to support the claim (hypothesis) of the scientist.  What do you think a scientist should do in the case that the evidence does not support the claim (hypothesis)?  Explain what you think should be the next steps for the scientist.

Due: Monday, October 21, 2013.

A cause and effect relationship is when one event or characteristic results in another.  Scientists attempt to understand and explain cause and effect relationships so that they can help prepare the world for future events and conditions, while searching for immediate solutions to prevent/reduce/address current problems and conditions.

Scientists often use the transitional "signal" words and phrases to indicate cause and effect relationships. You can explain a cause and effect relationship using these words and phrases, and/or identify cause and effect relationships written by other scientists upon spotting these words and phrases in published scientific studies.

As scientists, we make observations, and then allow those observations to inspire scientific questions. Consequently, these fascinating questions drive us to investigate for answers.  One observation scientists have noted worldwide is the dramatic increase in carbon dioxide, methane, and nitrous oxide in the Earth's atmosphere over the past 50 years.  What is the cause of this change?  What is the effect of this change?  You might ask?

Well, lets first take it back to the basic composition and function of the Earth's atmosphere.  The Earth's atmosphere is made up of a mixture of gases-- mostly Nitrogen, Oxygen, water vapor (the gas state of water)-- which is held in place by Earth's gravity.  The atmosphere acts like a blanket for the Earth, keeping it nice and warm, while protecting it from the Sun's harmful ultraviolet rays.  

The recent increase in carbon dioxide, methane, and nitrous oxide (also known as "greenhouse gases") in the Earth's atmosphere has a similar effect of adding more mass to a blanket: more heat gets trapped underneath, and the temperature rises. This phenomena of rising temperatures in the Earth's atmosphere due to the increase in greenhouse gases is called global warming.  But what is the cause of the increase in these greenhouse gases?  Here is what the students of MS 88 concluded upon examining a series of images and captions from an article published by NASA:

• “People want corn and corn products faster and cheaper.  As a result, more chemical fertilizers are used, which give off nitrous oxide.  Therefore, there is an increase in nitrous oxide in the Earth’s atmosphere.”
• “People around the world love McDonalds.  Consequently, the amount of livestock increases, which produce more methane gas.  As a result, there is an increase in methane gas in the Earth’s atmosphere.”
• "People buy more and waste more.  Therefore, landfills are packed, giving off a ton of methane gas.  This leads to an increase in methane gas in the Earth’s atmosphere.”
• “People love to drive big, fancy cars.  That is why more gasoline is burned, putting more carbon dioxide in the atmosphere.  Therefore, there is an increase in carbon dioxide in the Earth’s atmosphere.”
• “People use and waste a lot of paper products.  Therefore, more forests, which usually absorb carbon dioxide from the atmosphere, are cut down.  As a result, there is an increase in carbon dioxide lingering in the Earth’s atmosphere.”
• “People love their electronic gadgets.  Consequently, more fossil fuels are burned to provide electricity.  Therefore, there is an increase in carbon dioxide in the Earth’s atmosphere.”

To learn more about what other scientists are observing and predicting to be the effects of global warming, check out the following websites:

• http://environment.nationalgeographic.com/environment/global-warming/gw-effects/
  
• http://planetsave.com/2009/06/07/global-warming-effects-and-causes-a-top-10-list/
  
• http://www.climatehotmap.org/global-warming-effects/
• http://timeforchange.org/cause-and-effect-for-global-warming

Homework: Read at least two of the articles above.  Then write 3 different effects of the increase in carbon dioxide, methane, and nitrous oxide in the Earth's atmosphere.  Make sure to use the transitional cause and effect "signal" words (above), and write in complete sentences.  Use the example sentences to help get you started.  Remember, we are discussing EFFECTS this time, not causes.

• "The result of the increase in carbon dioxide, methane, and nitrous oxide in the Earth's atmosphere is ________________."
• As a result of the increase in carbon dioxide, methane, and nitrous oxide in the Earth's atmosphere, __________________."
• "The effect of the increase in carbon dioxide, methane, and nitrous oxide in the Earth's atmosphere is. _______________."
• "One effect of global warming due to the increase in greenhouse gases is ____________."

Rachel Carson 
1907 - 1964

Rachel Carson was an American conservationist and marine biologist who is best known for advancing the modern global environmental movement.  Her controversial book, Silent Spring, brought attention to the dangerous effects she believed were caused by the use of synthetic pesticides.  The book ultimately inspired a nationwide ban on DDT and other pesticides, and the creation of the U.S. Environmental Protection Agency.

Articles

• http://www.famousscientists.org/rachel-carson/
  
• http://www.rachelcarson.org/
  
• http://www.fws.gov/northeast/rachelcarson/carsonbio.html
  
• http://ecotopia.org/ecology-hall-of-fame/rachel-carson/biography/
  

Videos

• The Journal: Rachel Carson's Legacy 
  
• Biography.com: Rachel Carson

Charles Darwin 
1809 - 1882

Charles Darwin was a British naturalist who proposed the theory of evolution based on natural selection.  Natural selection is the process in which the stronger organisms survive to reproduce and pass on their traits (genes), while the weaker do not.  Darwin spent five years at sea on the HMS Beagle (boat), where he observed an incredible diversity of animal and plant species.  When the Beagle reached the Galápagos Islands, he noticed that each species was uniquely adapted to its immediate environment.  This observation led him to ask the questions that became the basis of his scientific explanation: living things have evolved in an orderly manner over many generations, and continue to evolve today.  After 23 years of study, he published his theory of evolution in The Origin of Species by Means of Natural Selection. 

Articles

• http://www.famousscientists.org/charles-darwin/
  
• http://www.livescience.com/474-controversy-evolution-works.html
  
• http://www.britannica.com/EBchecked/topic/151902/Charles-Darwin
  
• http://www.bbc.co.uk/history/historic_figures/darwin_charles.shtml

Videos

• Greatest Discoveries: Darwin's Story
• Greatest Discoveries in Evolution: Natural Selection
• Biography.com: Charles Darwin

Robert Hooke 
1635 - 1703

Robert Hooke was an English physicist and inventor.  Hooke proved that both combustion (burning) and respiration (breathing) require air, and that sound does not travel in a vacuum.  He was one of the first men to build a Gregorian reflecting telescope and to suggest that Jupiter rotates on its access.  Hooke also studied numerous objects under microscopes and was the first to use the word cell to describe the patterns he observed.


Articles

• http://www.famousscientists.org/robert-hooke/
  
• http://www.biography.com/people/robert-hooke-9343172
  
• http://www.bbc.co.uk/history/british/civil_war_revolution/hooke_robert_beavon_01.shtml
  
• http://www.roberthooke.com/

Videos

• http://www.youtube.com/watch?v=HuVofeYsJN
• Building a Life: Robert Hooke

Carl Linnaeus 
1707 - 1778

Carl Linnaeus was a Swedish naturalist who developed the modern classification system for naming plants and animals.  This classification system is called binomial nomenclature, which consts of two words, the first being the genus and the second the species.  For example, Homo sapiens, the scientific name of the human, is an example of binomial nomenclature.  His method of classification allowed for clear and easy descriptions of plants, animals and minerals. 


Articles

• http://www.anbg.gov.au/biography/linnaeus.html
  
• http://www.ucmp.berkeley.edu/history/linnaeus.html
  
• http://www.macroevolution.net/linnaeus.html#.Uje2f8akrMs
• http://www.britannica.com/EBchecked/topic/342526/Carolus-Linnaeus
  

Videos

• Greatest Discoveries: Classification of Species 
• http://www.nhm.ac.uk/nature-online/science-of-natural-history/biographies/linnaeus/
  

Louis Pasteur
1822 - 1895

Louis Pasteur was a French chemist who founded modern microbiology.   Pasteur established that germs cause diseases and infections.  Before Pasteur, people believed that diseases were generated spontaneously.  However, Pasteur's experiments proved that microorganisms are the true cause of many diseases. 
His early work with fermentation led him to invent to process of pasteurization.  He developed vaccines for anthrax, chicken cholera, and rabies.


Articles

• http://www.famousscientists.org/louis-pasteur/
  
• http://www.sciencekids.co.nz/sciencefacts/scientists/louispasteur.html
  
• http://www.biography.com/people/louis-pasteur-9434402
  
• http://www.britannica.com/EBchecked/topic/445964/Louis-Pasteur
  

Videos

• About.com: Profile of Louis Pasteur 
• Biography.com: Louis Pasteur

James Watson & Francis Crick
(1928 -  ) & (1916 - 2004)

James Watson (American) & Francis Crick (British) are biologists who identified the structure of Deoxyribonucleic Acid, otherwise known as DNA.  By analyzing the patterns cast by x-rays striking DNA molecules, they discovered that DNA has the structure of a double helix, two spirals linked together by bases in ladder-like rungs.  Their discovery formed the basis of molecular genetics.  By understanding the structure of DNA, we better understand ourselves and our families through the study of hereditary disease, and the evolution of human life. 

Articles

• http://www.bbc.co.uk/history/historic_figures/watson_and_crick.shtml
  
• http://www.biographyshelf.com/francis_crick_james_watson_biography.html
  
• http://www.life123.com/parenting/education/biographies/james-watson-and-francis-crick.shtml
  

Videos

• People and Discoveries: Watson and Crick Describe the Structure of DNA
• http://www.biography.com/people/james-d-watson-9525139
  
• http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna