Biogenesis
From Wikipedia, the free encyclopedia
Biogenesis is the process of lifeforms producing other lifeforms, e.g. a spider lays eggs, which form into spiders.
The term is also used for the assertion that life can only be passed on by living things, in contrast to abiogenesis, which holds that life can arise from non-life under suitable circumstances, although these circumstances still remain unknown.
Until the 19th century, it was commonly believed that life frequently arose from non-life under certain circumstances, a process known as spontaneous generation. This belief was due to the common observation that maggots or mould appeared to arise spontaneously when organic matter was left exposed. It was later discovered that under all these circumstances commonly observed, life only arises from life.
A second, obsolete meaning of biogenesis was given by the French Jesuit priest, scientist and philosopher Pierre Teilhard de Chardin to mean the origin of life itself — now usually referred to as abiogenesis — reflecting the modern belief that the origin of life was from non-life.
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[edit] Law of biogenesis
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- "La génération spontanée est une chimère" ("Spontaneous generation is a dream") (Louis Pasteur)
Pasteur's (and others) empirical results were summarized in the phrase, Omne vivum ex vivo (or Omne vivum ex ovo, Latin for "all life [is] from life", also known as the "law of biogenesis". They showed that life does not currently spontaneously arise in its present forms from non-life in nature.
The "law of biogenesis" is not to be confused with Ernst Haeckel's Biogenetic Law. [1] [2]
No life has ever been observed to arise from non-living matter. However, the Miller-Urey experiment did show that amino acids, and other subsequent organic compounds, can be synthesized from simple carbon atoms in the early earth conditions.
[edit] Human attempts to create life
Charles Darwin in a letter to J.D. Hooker of February 1st 1871, made the suggestion that life may have begun in a "warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity, etc. present, that a protein compound was chemically formed ready to undergo still more complex changes, at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed." Thus, it is the presence of life itself which prevents "spontaneous generation" from occurring on Earth today.
A number of efforts have been made to bring life from non-life, but there has been little success. J. B. Burke attempted to produce small living cells from inorganic matter by means of radium were unsuccessful; the radiobes produced were merely bursting gas bubbles of microscopic size. Pflüger produced cyanic acid, which he compared to half-living molecules, but it was merely a dead chemical compound. The Russian Scientist Alexander I Oparin suggested that we need to understand that the conditions on Earth at the time of the origin of life must have been very different from how they are today. The Miller-Urey experiment confirmed Oparin's hypothesis by producing some of the organic components of life, from an atmosphere of methane, ammonia and water vapour. The earth's early atmosphere is pure speculation without basis. The most basic amino acids were formed in millers test tube but the atmosphere required to make them killed them soon after.
In 2002, scientists succeeded in constructing an artificial and "functioning" (able to infect and kill mice) Polio virus. Other viruses have since been synthesized. These experiments do not qualify as true examples of abiogenesis, since viruses do not meet the standard biological criteria for life. Primarily, they do not respond to stimuli, they are ataxic, they lack the ability or the mechanics to grow or reproduce on their own, and they do not possess cells.
Still, proponents of the idea of abiogenesis cite these results in support of their position, stating that both "non-living" viruses and "living" bacteria are solely "molecular machines" of different complexity. Many of them expect scientists to be able to synthesize the latter when the necessary technology has advanced to a sufficient level, thus proving the possibility of abiogenesis. Additionally, some point to lesser-known and controversial experiments such as those performed by Andrew Crosse as examples of abiogenesis.
Critics of Abiogenesis point out that (thusfar) life cannot be created without outside intelligence forcing environmental conditions necessary for life, so that "all by itself" seems extremely unlikely.
[edit] Law of Biogenesis and Creationism
The narrower meaning of the term Biogenesis is the basis of Creation biology, which holds that since life cannot arise spontaneously from non-life, life must, of necessity, have been created by a "supernatural" being, typically the Christian God. Supporters of the theory of evolution argue that creationists misuse the law of biogenesis to support their arguments. For example:
- "The spontaneous generation that Pasteur and others disproved was the idea that life forms such as mice, maggots, and bacteria can appear fully formed. They disproved a form of creationism. There is no law of biogenesis saying that very primitive life cannot form from increasingly complex molecules.
They also say that creationists' use of the law as an argument against theories of common descent is an example of the fallacy of false dilemma, since it is imaginable that a creator god created the LUCA or one of its ancestors, from which point on evolution occurred in a guided or unguided fashion. Creationists respond that abiogenesis is not a form of creationism, because it holds that life arises spontaneously, while creationism holds that life was deliberately created. Further, since the hypothesized development of "primitive life" from "increasingly complex molecules" has never been observed, there remains no comprehensive scientific justification for believing it has ever occurred. Finally, they argue that once it has been conceded (as is conceded by theistic evolution) that the original cell was created by a divine being, there is no reason to believe He could not have created life in a variety of forms.
