At first scientists believed that living things came from non living things.
This theory was called spontaneous generation ( Abiogenesis) .
Louis Pasteur(disproved it)
Experiments on Spontaneous Generation (Abiogenesis)
1668—Francisco Redi proposed the hypothesis that flies laying eggs on meat were responsible for the appearance of maggots.
If flies are prevented from laying their eggs on meat, then no maggots will appear on the meat.
HYPOTHESIS: Flies produce maggots . PROCEDURE Controlled Variables: jars, type of meat, location, temperature, time Manipulated Variables: gauze covering that keeps flies away from meat Uncovered jars Covered jars Several days pass Maggots appear No maggots appear Responding Variable: whether maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. Figure 1-8 Redi’s Experiment on Spontaneous Generation http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbp&wcsuffix=1012
mid-1700s— John Needham attacked Redi’s work. He claimed spontaneous generation could occur under the right conditions. He sealed a bottle of gravy and heated it. Several days later it was full of microorganisms (little animals).
Lazzaro Spallanzani read about Redi and Needham’s work and decided to improve on Needham’s experiment.
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:
Then in the mid 1800’s a man named Pasteur disproved this theory and it was replaced with a stronger theory called biogenesis , which states that all living things can only come from other living things. (Support Cell theory)
Experiments on Spontaneous Generation http://www.phschool.com/atschool/phsciexp/active_art/redi_pasteur_experiment/index.html
Make a flip flap booklet on Spontaneous Generation Spontaneous Generation Francisco Redi’s Experiment Pg. 9 Draw and explain his experiment Lazzaro Spallanzani Pg. 11 All Facts know about the topic Pg 8 What is it? Louis Pasteur (Pg. 12)
2. Cheek cells do not move on their own, so you will not find two organelles that function for cell movement. Name these organelles.
3. The light microscope used in the lab is not powerful enough to view other organelles in the cheek cell. What parts of the cell were visible?
4. List 2 organelles that were NOT visible but should have been in the cheek cell.
5. Is the cheek cell a eukaryote or prokaryote? How do you know
6. Keeping in mind that the mouth is the first site of chemical digestion in a human. Your saliva starts the process of breaking down the food you eat. Keeping this in mind, what organelle do you think would be numerous inside the cells of your mouth?