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The hypothetical process by which living organisms develop from nonliving matter. (also called Abiogenesis) Pieces of cheese and bread wrapped in rags and left in a dark corner were thus thought to produce mice. Because after several weeks, there were mice in the rags. And it was also thought that putrefying meat would produce maggots.

Francesco, is my dinner “Redi”!

Redi read a book by William Harvey in which Harvey speculated that organisms such as insects, worms, and frogs do not arise spontaneously, as was then commonly believed, but grow from seeds or eggs which were too small to be seen. In 1668, in one of the first biological experiments with proper controls, Redi set up a series of flasks containing different meats, half of the flasks sealed, half open.

He then repeated the experiment but, instead of sealing the flasks, covered half of them with gauze so that air could enter. Although the meat in all of the flasks rotted, he found that only in the open and uncovered flasks, which flies had entered freely, did the meat contain maggots. Though correctly concluding that the maggots came from eggs laid on the meat by flies, Redi, surprisingly, still believed that the process of spontaneous generation applied in such cases as gall flies and intestinal worms.

- He was able to build microscopes which magnified objects over 200 times their size. - With the aid of his microscope, he describes the matter taken from his own teeth as having "many very little living animalcules" and continues by explaining the animal's structures and movements. - Leeuwenhoek gained recognition as the founder of the living microscopic organisms we now call bacteria. Cross section of a 1 yr old ash tree.

(1822 – 1895)

-Louis Pasteur’s discovery that most infectious diseases are caused by germs, known as the "germ theory of disease," is one of the most important in medical history. -His work became the foundation for the science of microbiology and a cornerstone of modern medicine.

Pasteur's phenomenal contributions to microbiology and medicine can be summarized as follows: 1: He championed changes in hospital practices to minimize the spread of disease by microbes.

2: He discovered that weakened forms of a microbe could be used as an immunization against more virulent forms of the microbe.

3: Pasteur found that rabies was transmitted by agents so small they could not be seen under a microscope, thus revealing the world of viruses. As a result he developed techniques to vaccinate dogs against rabies, and to treat humans bitten by rabid dogs.

4: Pasteur developed "pasteurization," a process by which harmful microbes in perishable food products are destroyed using heat, without destroying the food.

-Alexander Ivanovich Oparin described the hypothetical conditions which he felt would have been necessary for life to first come into existence on early Earth. This hypothesis is referred to as the Oparin Hypothesis. -He theorized that the first atmosphere was made largely of water vapor (H 2 O), carbon dioxide (CO 2 ), carbon monoxide (CO), nitrogen (N 2 ), methane (CH 4 ), and ammonia (NH 3 ).

-As the surface of Earth cooled again, torrential rains of this mixture formed the first seas, the “primordial soup.” - Lightening, ultraviolet (UV) radiation, volcanic action all were more intense than they are now. These energy sources may have provided the energy necessary to create the chemical reactions needed to rearrange early molecules into those which would be the precursors to life on earth!

of-life-chemistry/

-By the 1950s, scientists were in hot pursuit of the origin of life. -In 1953 Miller and Urey, working at the University of Chicago, conducted an experiment which would change the approach of scientific investigation into the origin of life. -Miller took molecules which were believed to represent the major components of the early Earth's atmosphere (methane, ammonia, hydrogen, and water) and put them into a closed system.

-Next, he ran a continuous electric current through the system, to simulate lightning storms believed to be common on the early earth. -At the end of one week, Miller observed that as much as 10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins. -Miller's experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth.