What is Critical Thinking? A precise process of skillfully applying logic & reason to solve real world problems… This is not only how we solve problems but also how scientists examine the world around them!

The Scientific Method A series of logical steps to follow in order to solve problems--using critical thinking

More on the Scientific Method: Not followed same way every time Research may be necessary, before writing a hypothesis A creative experiment must be designed and carried out to test the hypothesis Data must be collected and analyzed before a conclusion(s) can be made

Famous Experiments: Spontaneous generation = life could arise from non-living forms Why would anyone believe spontaneous generation? They could only observe what there eyes could see—no microscopes…

Spontaneous Generation (cont.) Redi’s Experiment: Redi put meat into three separate jars.Jar 1 was left open Jar 2 was covered with netting Jar 3 was sealed from the outside Biogenesis = life could only come from other life forms 1668: The experiment of Francesco Redi: Redi's Problem Where do maggots come from? Hypothesis: Maggots come from flies. What are the independent and dependent variables??

Spontaneous Generation (cont.) Spallanzani’s Experiment: In the middle 1700’s, Lazzaro Spallanzani continued the work to show spontaneous generation was not possible: Spallanzani's Problem What causes microbes to form in decaying broth? Hypothesis: Microbes come from the air. Boiling will kill microorganisms.

Spontaneous Generation (cont.) Spallanzani’s Experiment: Flask-1Left Open,Turned cloudy, Microbes were found Flask-2 Sealed,Turned cloudy,Microbes were found Flask-3Boiled and left open Turned cloudy, Microbes were found Flask-4Boiled and sealed, Did not turn cloudy, Microbes not found