How Scientists Work  Scientists use the scientific method which are the universal steps used for all science fields  Scientific Method Steps  Ask a Question/Problem  Form a Hypothesis  Experiment  Record/Analyze Data  Draw Conclusion

Question? Problem – Which type of substrate will a Venus Flytrap grow best in? Research the Venus Flytrap

Hypothesis My Hypothesis – If … Then… statement – If the Venus Flytrap is put in sand then it will grow taller

Controlled Experiment In a controlled experiment only one (1) variable is changed All other variables are kept constant A variable is a factor in an experiment

Controlled Experiment Variables – Independent - variable that is intentionally changed, also called manipulated variable – Dependent -what is being measured or observed, also called responding variable – Constant - variables that are not changed in experiment

Controlled Experiment What are our variables? Independent Variable Substrate( clay, sand, dirt) Dependent Variable Height of flytrap Constant Variable Water, temp., sunlight, etc.

Analyze Data Determine findings – Flytrap in soil grew 5 centimeters in 1 week – Flytrap in sand did not grow at all in 1 week – Flytrap in clay grew 2 centimeters in 1 week

Conclusion Describe your data from the experiment – My hypothesis was not supported by my data. – The Venus Flytrap grew best in soil rather than sand or clay over a week long period.

How Scientists Work Objectives:  Describe early experiments  Explain the difference b/w a theory and a law

Spontaneous Generation The belief that certain living things can come from inanimate objects, without the need of a living ancestor – Some common beliefs included: snakes come from horse hair in water, mice come from cheese wrapped in shirts, and maggots come from rotting meat

Redi’s experiment

Needham Did an experiment to attack Redi’s findings Sealed a flask, heated it, and left it out Microbes were found Why do you think that happened?

Spallanzani Redid Needham’s experiment, but this time he boiled 2 flasks, then immediately sealed one of them and left the other open The sealed flask had no microbes

Experiment: Step 1

Experiment: Step 2

Experiment: Step 3

Pasteur 200 years later people were STILL fighting over spontaneous generation Pasteur ended it all with this experiment…….

Pasteur’s experiment

The impact of Pasteur’s Work Pasteur saved the French wine industry, which was troubled by unexplained souring of wine. He saved the silk industry, which was endangered by a silkworm disease. He began to uncover the nature of infectious diseases, showing that they were the result of microorganisms.

Germ Theory All this lead to the germ theory- that infectious diseases are not the result of bad luck, but are instead a result of microbes, or germs

“I have a theory” vs Scientific Theory Common usage of theory-guess or prediction (a hypothesis!) Scientific meaning=well tested explanation that unifies a broad range of observations Allows scientists to make accurate predictions about new situations; must be falsifiable

Theories No theory is considered “absolute truth” Theories may be revised, replaced as new information is found

Scientific Law A statement of fact meant to explain, in concise terms, an action, or set of actions – Can be expressed as an equation Laws must be simple, true, universal, and absolute

The difference Theory is dynamic and complex Law explains one action Theory explains a GROUP of RELATED phenomena

Analogy: A scientific law is like a slingshot. A slingshot has one moving part--the rubber band. If you put a rock in it and draw it back, the rock will fly out at a predictable speed, depending upon the distance the band is drawn back. An automobile has many moving parts, all working in unison. An automobile is a complex piece of machinery. Sometimes, improvements are made to one or more component parts. A new set of spark plugs that are composed of a better alloy that can withstand heat better, for example, might replace the existing set. The function of the automobile as a whole remains unchanged. A theory is like the automobile. Components of it can be changed or improved upon, without changing the overall truth of the theory as a whole.