Science and the Scientific Method

Long Ago Until 1859 the common belief was that life could appear from non-living things. This was called spontaneous generation. The Slow Death of Spontaneous Generation occurred from 1668 to ?What is spontaneous generation?

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Controlled Variables: jars, type of meat, location, temperature, time Independent Variables: gauze covering that keeps flies away from meat Uncovered jarsCovered jars Several days pass Maggots appearNo maggots appear Dependent Variable: whether maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Section 1-2 Redi’s Experiment on Spontaneous Generation (1668) Go to Section:

John Needham (1745) Everyone knew that boiling killed microorganisms (common knowledge) John Needham proposed to test whether or not microorganisms appeared spontaneously after boiling. He tried to disprove Redi’s conclusion –He boiled chicken broth, –put it into a flask, –sealed it, –and waited sure enough, microorganisms grew. Needham claimed victory for spontaneous generation. ?Do you see a problem with this experiment?

Spallanzani “You missed a variable, for life to be generated you need contact with the air” Is this true?

Gravy is boiled.Flask is open. Gravy is teeming with microorganisms. Gravy is boiled. Flask is sealed. Gravy is free of microorganisms. Section 1-2 Figure 1-10 Spallanzani’s Experiment Go to Section: ?What is the difference between Needham’s Experiment and Spallanzani’s Experiment?

Broth is boiled.Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms. Section 1-2 Figure 1-11 Pasteur’s Experiment Go to Section: ?How is Pasteur’s experiment different from Spallanzani’s? ?When did the microorganisms begin to grow in Pasteur’s experiment?

Scientific Theory Science Theory- an explanation of a natural phenomenon that is supported by a large body of scientific evidence obtained by many different investigations and observations. A theory remains valid only if every new piece of information supports it. If available information does not support a theory, then the theory is disproved. New discoveries in science occasionally change a theory. ?Can a theory change and, if it does, how? Scientific Law- facts of nature that are generally known to be true. Stronger than a theory Hypothesis  Theory  Law

Nature of Science Science never reaches “Fact” Constantly, new technologies and ideas arise that disprove current theories. Science gets as close to “Fact” as possible as people fail to disprove a concept. ?Why does science never reach “fact”?

Recipe for Bees About 2000 years ago, a Roman poet wrote these directions for producing bees. Is this science and is this an experiment?

Yes! At the time with the current knowledge this could be repeated and have a similar result

What IsThe Goal of Science To investigate and understand nature To explain events in nature To use those explanations to make useful predictions

Scientific Method 1. Problem 2. Research 3. Hypothesis 4. Experiment 5. Analysis 6. Conclusion

Independent Variable is the amount of sugar. Dependent variable was density we wanted to see if water would float. Control the water Constant: The amount of water, dye, spoons, cups, test tubes, temp, Procedure:Mixed measured water, sugar with water, dye then we put it in a test tube. 14

Then put food coloring in the other water then, tilted test tube poured in the water inside the tube and tested it to see if it would float. Results Water can float on a sugar solution. 15

Scientific Method Identify the Problem – predict outcome? Form a Hypothesis Set Up a Controlled Experiment Record and Analyze Results Draw a Conclusion Repeat and Retest – magic # is 3 of same!

Vocabulary Hypothesis – A prediction about a possible answer to a scientific question. What will happen to the independent variable and the dependent variable during the expermiment. The plant is dying because it needs to be watered. It is a statement which is an educated guess and it is testable

Vocabulary Independent variable – The variable you the scientist change in an experimental group. Cause Often graphed on the X- Axis

Vocabulary Dependent variable – Part of the experiment that a scientist wants to observe and measure. You do not have direct control over the results of this variable. Effect Graphed on the Y-Axis Example:How low did the blood sugar drop? 19

Vocabulary Experimental group – In an experiment this is the group that the independent variable IS given to. It is compared to the control group. Experimental Group: Plant A (watered) Control Group: Plant B is left the same (not watered)

Vocabulary Control group the group that is used compare your results this is the group you do NOT give your independent variable. Often is give the Placebo (FAKE PILL) Controls are needed to eliminate other explanations of experimental results. For example, suppose a researcher feeds an experimental artificial sweetener to thirty laboratory rats and observes that eight of them die of dehydration. Can we determine without doubt that the artificial sweetener killed them? The underlying cause of death could be the sweetener itself or something unrelated.

Vocabulary Independent variable – Part of the experiment that a scientist purposely changes; also known as manipulated variable Dependent variable – Part of the experiment that a scientist wants to observe, which may change in response to the manipulated variable; also known as a responding variable. You do not have direct control over this variable. Controlled variable- All the variables that are kept the same (held constant during the entire experiment.

DR. S Insulin Pill PatientStart Blood Sugar Level Final Blood Sugar Level Student Student 2184 Student 3185 Student

The Effect of Fertilizer on Plant Growth Question: Will fertilizer increase plant growth? Hypothesis: Materials: Tomato seeds, Water, Flower pots Miracle Grow fertilizer Variables: Independent Variable: Dependent Variable: Control: Constants: 24

Results PlantDay 11Day 12Day13Day 14 Control 10 cm.25 cm1.0 cm Control 2O cm0 cm.75 cm1.1 cm Fertilizer 1.5 cm1.4 cm4.9 cm5.9 cm Fertilizer 21.0 cm1.8 cm4.5 cm5.8 cm 25

Results: 26

Vocabulary Controlled experiment – a test of the effect of a single variable keeping all other variables the same. Change “only one variable” in an controlled experiment Variable – anything that you change or changes as a result of what you do

Vocabulary Dependent variable – Part of the experiment that a scientist wants to observe, which may change in response to the manipulated variable; also known as a responding variable. You do not have direct control over this variable. Die Live Why is the dependent variable referred to as “The Effect”? The dependent variable is dependant on the independent variable

I want to know if more light would cause hens to lay more eggs. In this experiment, what would be the only thing (variable) I would want to change? Why would I not want to also change the amount of food I give them?

Explaining the evidence Hypothesis- a statement that is a possible explanation for a set of observations or answers to a scientific question  A hypothesis must be testable. (not useful if it can’t be tested)

Vocabulary Experiment: Data collection – collection of evidence; inform Data Analysis – Make a graph from the information gathered from observations

Vocabulary Observation - use of one or more of the senses—sight, hearing, touch, smell, and sometimes taste—to gather information –Qualitative observations involve characteristics that cannot be easily measured or counted. These are descriptions. –Quantitative observations involve numbers

Vocabulary Data analysis - Observing your data, picking out the important results, and making sense of the data. Graphs are very useful in analyzing data Data is anything collected through observation in an experiment

A few types of graphs Line Graph Bar Graph Pie Chart There are times where one graph is far better than the others

Vocabulary Inference - logical interpretation based on prior knowledge and experience For example, researchers might test small quantities, or samples, of water from a reservoir. If samples collected from different parts of the reservoir are all clean enough to drink, the researchers may infer that all the water in the reservoir is safe to drink.

Vocabulary Conclusion - Using the evidence of an experiment to determine whether the hypothesis was supported or refuted (wrong).

State the Problem Scientific Method It Stinks!

Form a Hypothesis The room stinks because a rat died in a cabinet The room stinks because someone passed gas –Pick only one hypothesis to test, you can come back to the others if you conclude the first one is wrong. –Pick the most likely hypothesis to test first Scientific Method

Set Up a Controlled Experiment Have a control to compare your results to- in this case the room before to odor Only Change One Variable –The variable changed must make sense –I will turn on the exhaust and see if it still smells bad 5 minutes later –If it does not smell bad it was only something temporary Scientific Method

Record and Analyze Results It still smells bad after 5 minutes Scientific Method

Draw a Conclusion My Hypothesis about the flatulence was incorrect  go back to step one and test another hypothesis Scientific Method

Station 3 1. Define abiogeneisis 2. What is the control variable of this experiment? What is the Independent variable of this experiment? Did li 42

Station 2 What did Louis Pasteur discover? 43