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330
Aristotle
Aristotle thought life came from the 4 terrestrial elements: earth, air, fire, water. He thought a mixture of these hot, cold, dry and wet principles, along with elements and one’s “soul”, were mixed in each part of the body to make the properties of living organisms. -
Period: 330 to
Spontaneous Generation Evolution
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500
Anaximander's Proposal
He said that life began spontaneously and believed everything came from the basic nature of the universe. Anaximander attempted to give natural explanations for things that were previously credited to supernatural beings. -
Recipes to Create Life
Spontaneous generation allowed for a lot of bizarre beliefs. People believed that they could create life from non-living thingsPeople created recipes like the following:
o snakes could arise from horse hairs standing in stagnant watero mice from decomposing foddero maggots from dead meat (strongest evidence for existence of SG)o and even mice from cheese and bread wrapped in rags and left in a corner. -
Robert Hooke's Cell Theory
Hooke cut thin strips of cork and observed them under a microscope. He then discovered empty spaces in the “walls” of the cork he had cut, proceeding to name the spaces "cells". This term stuck and Hooke was recognised for determining the essence of all life. -
Anton Van Leuwenhoek
Anton was the first to describe living cells. Hooke approved the results of one of Leeuwenhoek's experiments, and confirmed he saw what they called ‘animalcules” in pond water. In order to see these animalcules he used single lens microscope which he had handcrafted. -
Francesco Redi's Experiment
Redi was the first person to seriously challenge “spontaneous generation”. During his time, the spontaneous generation recipe that “maggots were born from rotting meat” was believed by many. However, Redi believed that maggots were products of eggs laid by flies on the meat. He challenged this hypotheses by putting meat in flasks, some air-exposed, some sealed, and some covered with gauze. As expected, maggots only came from the open jar where meat was exposed to flies allowing them to lay eggs -
Invention of the Microscope
The microscope was invented, and it supported rather than challenged he belief of spontaneous generation because even more organisms appeared to be born spontaneously. A new recipe to create “animalcules” was developed "place hay in water, wait for a several days".o new animalcules created -
John Needham Proposes a Conclusive Experiment
John knew that boiling destroyed microorganisms. So he tested to see if microorganisms showed up spontaneously after boiling. He boiled chicken broth, put it into a sealed flask, and waited. Miicroorganisms grew and Needham was awarded credit for his experiment proving "spontaneous generation" right -
Lazzaro Spallanzani's Experiment
Lazzaro was an Italien priest who wasn’t convinced by Needham’s experiement. He said that microorganisms may have entered the broth from the air after the boling of the broth. So, he adjusted Needham’s experiment by putting chicken broth in sealed flask, with some air drawn off to create a partial vaccum, he then boiled the broth. No microorgamisms appeared, but supporters of spontaneous generation said this simply proved spontaneous generation could not occur without air. -
Matthias Jakob Shleiden Cell Theory
Shleiden was a botanist who made the first conclusion of cell theory by saying that all plant materials are made of cells. He claimed a budding new plant, arose from single cell and that the cell is the basic building plant of all plant tissue. This theory was a strong contributor to the disapproval of spontaneous generation. -
Louis Pasteur's Study of Spontaneous Generation
Pasteur's famous experiment was the first to completely disprove the theory of spontaneous generation. His experiment was a variation of Needham and Spallanzani experiments. He boiled meat broth in flask, heated the neck of flask in a flame until it was bendable, and bended into shap of s, this allowed air to enter flask, but not for air-borne microoganisms to – no microoganisms grew. Upon tilting the flask he found that the microorganisms trapped in the neck, progressed to thrive in the broth.
