Scientific Method Yes, people really do use it!

Spanish-American War, late 1800’s US soldiers were stationed in Cuba More soldiers died of Yellow Fever (YF) than bullets Symptoms of yellow fever: –Fever –Nausea –Muscle pain –Vomiting blackened blood – “the black vomit” –Ghastly yellow skin - jaundice

Death Wagon

The Reed Commission US Army Yellow Fever Commission Post Spanish-American War research in Cuba

Walter Reed Knew: old way to fight disease –Isolate sick –Boils clothes, sheets –Sterilize plates, cups.. Realized: The disease was still spreading Army Research Doctor

Findlay’s hypothesis Carlos Juan Findlay, Cuban doctor Thought disease was spread by mosquitoes –Had been saying it for 20 years –Called “The Mosquito Man” Most people did not believe this

Reed’s Experiment Group 1 20 days used filthy clothes, sheets, utensils of infected YF soldiers Protected from mosquitoes with screens Group 2 20 days Used fresh clothes, clean sheets, utensils Isolated from infected YF soldiers Not protected from mosquitoes 3 doctors joined this group Formites Theory – touching infected stuff Aedes Theory – mosquito genus

Results Group 1 – no one developed yellow fever Group 2 – many including all 3 doctors (1 died) became sick US pulled out of Cuba (republic of Cuba) left a naval base - Guantánamo Bay (1901) Once the disease was under control in Panama, the US began considering building the Panama Canal.

Yellow Fever Quarantine

Bottom Line Science requires much more than observation. Scientists must develop explanations for their observations and then use the scientific method to TEST those observations. What steps to the Scientific Method can you identify in the Yellow Fever problem?

Scientific Method? Time to create our notes. Problem identified Developed a hypothesis Identify independent (manipulated) & dependent (responding) variables Establish a control group Experiment & test your hypothesis Record & organize your data/what you see-- pictures, graphs, measurements Statement about what happened---conclusion Inform/communicate your findings

Independent (manipulated) & Dependent (responding) Variables Manipulated variable is what you change Responding variable is what you measure Listen to the tomato plant example Identify each variable and constant Make a space on your paper for each You and your lab partners must determine which parts are variables and constants

The tomato plants 12 tomato plants were grown in 48” pots Each plant received the same light & water for 8 weeks during the summer 3 plants received nitrogen fertilizer 3 plants received compost tea 3 plants received P-N-K fertilizer 3 plants were not fertilized Weekly heights were measured Number of fruits were collected