MadSci Network: Microbiology

Re: heterotroph or autotroph?

Area: Microbiology
Posted By: Marcy LaViollette, Senior, chemical engineering, Capital High School
Date: Tue Nov 18 17:54:44 1997
Area of science: Microbiology
ID: 877297469.Mi

An explanation of how life originated was suggested by a group of scientists, including the Russian biochemist Alexander I. Oparin, who wrote the book, The Origin of Life (1936). In it he proposes that in the "hot thin soup" of the primitive earth, organic molecules formed. Some of the larger, complex molecules formed aggregates. These aggregates (also known as coacervates) incorporated molecules from the ocean as food. In this form they were heterotrophs. The respiration of the heterotrophs must have been anaerobic as there was little or no oxygen in the atmosphere at the time. They obtained their energy by fermentation, and by doing so, added quantities of carbon dioxide to the atmosphere. Some of the heterotrophic aggregates developed a method of using carbon dioxide to manufacture their own food, and so became pioneer autotrophs. These autotrophs added oxygen to the atmosphere, and so evolution continued.

Conformation of this hypothesis has been performed by Dr. Stanley Miller in his laboratory experiments. He boiled water continuously in a flask containing methane, ammonia, hydrogen, and water vapor. These materials were subjected to electric discharges. After a week of duplicating the earth's primitive conditions in this way, Miller found that a number of organic molecules, including amino acids, had been formed in the flask.

Keep asking questions!

                                     -Marcy LaViollette

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