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days in an open bowl. The liquid soon became cloudy with millions of protozoa, bacteria and fungi.
This theory of spontaneous generation was largely disproved by microbiological studies of Louis Pasteur (1822-1895). He argued that life was not created but fell into infusion from the air as cells or spores. Thus was spontaneous generation buried.
ORIGIN OF LIFE UPON EARTH-CHEMICAL EVOLUTION
When our earth was new, it was a mass of molten lava. Nothing could live in such conditions. But life did appear about a billion years ago. Was this not abiogenesis? Scientists wondered about what happened then. A.I. Oparin was the first to discuss the problem in 1938 and suggested that before the origin of life, there was some sort of chemical evolution. In 1953, Harold Urey and Miller constructed an apparatus wherein the four primitive gases--ammonia, hydrogen, methane, and water-vapour—were continuously circulated and subjected to electric sparks and heat in order to keep the water vaporized. Within a week, a number of organic substances were formed, of which amino acids were the most important. Now amino acids are the units from which proteins are made and proteins and nucleic acids are the least common multiples of life because viruses which are regarded to be on the border line of living and non-living, consist of but little else.
If proteins could be made from simple stuff like this, what about nucleic acids? Some scientists stated that not only nucleic acids but other important substances could be created in this way. Thus, before the appearance of life, the chemicals of life-were created. This is called “Chemical Evolution."
1. According to Biology, a virus is a very small organism, much smaller than bacteria or other classifiable micro-organisms, visible only in electron-microscope, consisting mainly of nucleic acid and protein molecules. It is unable to multiply outside a living tissue, in which it frequently causes disease, e.g., tobacco mosaic. In man, virus diseases include influenza.
A virus called Escherichia Coli consists of a coat made of proteins and a core of nucleic acid which is injected into the cell of the victim. Within a short time, the injected nucleic acid reproduces itself into hundred of new virus particles.
JAIN BIOLOGY
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