Main Idea LIFE COMES ONLY FROM LIFE Life

Main Idea LIFE COMES ONLY FROM LIFE

Life comes from life! • Scientists previously believed in spontaneous generation. • Definition: Spontaneous generation is the mistaken idea that living things can arise from non-living sources • Living things arise from living things through reproduction.

Can you believe it? • Thunderstorms were once believed to produce frogs and fish! • It was an ancient belief called spontaneous generation • The scientists below conducted research to disprove this belief: • Lazzaro Spallanzani Francesco Redi • John Needham Louis Pasteur

John Needham • Did experiments that seem to show there was a life force that produced spontaneous generation • His experiments consisted of briefly boiling a broth mixture, then cooling it in an open container to room temperature. • Later the flasks would be sealed and microbes would grow a few days later.

Lazzaro Spallanzani • An Italian scientist that proved micro-organisms could be killed by boiling. • He put broth in 4 flasks. • Flask 1 was left open, Flask 2 was sealed, Flask 3 was boiled and left open and flask 4 was boiled and then sealed. • Microbes were found in every flask but flask 4 thus contradicting Needham’s findings.

Francesco Redi • Italian doctor that proved flies do not arise from decaying meat. • He used covered and uncovered jars to show that flies laid eggs in the uncovered jars which produced more flies. • Covered jars were used as the manipulated variable.

Louis Pasteur • French chemist who designed experiments to further disprove theory of spontaneous generation. • He also designed the process for pasteurizing food.

Pasteurization

Assignment • Reading: Go back to the Moodle topic outline page and click on the resource titled, “What’s so special about life? ” • Answer the book questions on the following slides in your science notebook. Write the questions and the answers.

Questions • 1. Why do scientist's consider Earth’s environment to be so fragile? • 2. What are the two different “parts” that make up an ecosystem? • 3. What three critical factors determine which types of plants and animals can live in a particular biome? • 4. Louis Pasteur designed an experiment to disprove theory of spontaneous generation. What did his experiment confirm?

Assignment: Brainy Bits and Bytes • The following hypothesis has been suggested to you by your medieval friend, Arthur: • “If a sweaty shirt and 5 to 10 grains of wheat are placed in a dark container for 21 days, then they will transform into mice. ” • Propose an experiment to Arthur to test his hypothesis. • 1. Experiment: (5 pts. ) • 2. Predict whether or not your experiment will cause Arthur’s hypothesis to be rejected. Why or why not? (5 pts. ) • 3. What observations do you think Arthur made that led him to develop his original hypothesis? (5 pts. )