Biogenesis

This article is about the generation of life from existing life. For the medical clinic accused of selling performance-enhancing drugs, see Biogenesis baseball scandal. For other uses, see Biogenesis (disambiguation).

Biogenesis is the production of new living organisms or organelles. The law of biogenesis, attributed to Louis Pasteur, is the observation that living things come only from other living things, by reproduction (e.g. a spider lays eggs, which develop into spiders). That is, life does not arise from non-living material, which was the position held by spontaneous generation. This is summarized in the phrase Omne vivum ex vivo, Latin for "all life [is] from life." A related statement is Omnis cellula e cellula, "all cells [are] from cells;" this observation is one of the central statements of cell theory.

Biogenesis and abiogenesis

The term biogenesis was coined by Henry Charlton Bastian to mean the generation of a life form from nonliving materials, however, Thomas Henry Huxley chose the term abiogenesis and redefined biogenesis for life arising from preexisting life. The generation of life from non-living material is called abiogenesis, and is theorized to have occurred at least once in the history of the Earth, or in the history of the Universe (see panspermia), when life first arose.

The term biogenesis may also refer to biochemical processes of production in living organisms (see biosynthesis).

Spontaneous generation and its disproof

Main article: Spontaneous generation

The Ancient Greeks believed that living things could spontaneously come into being from nonliving matter, and that the goddess Gaia could make life arise spontaneously from stones – a process known as Generatio spontanea. Aristotle disagreed, but he still believed that creatures could arise from dissimilar organisms or from soil. Variations of this concept of spontaneous generation still existed as late as the 17th century, but towards the end of the 17th century, a series of observations and arguments began that eventually discredited such ideas. This advance in scientific understanding was met with much opposition, with personal beliefs and individual prejudices often obscuring the facts.

William Harvey (1578-1657) was an early proponent of all life beginning from an egg, omne vivum ex ovo. Francesco Redi, an Italian physician, proved as early as 1668 that higher forms of life did not originate spontaneously by demonstrating that maggots come from eggs of flies. but proponents of spontaneous generation claimed that this did not apply to microbes and continued to hold that these could arise spontaneously. Attempts to disprove the spontaneous generation of life from non-life continued in the early 19th century with observations and experiments by Franz Schulze and Theodor Schwann. In 1745, John Needham added chicken broth to a flask and boiled it. He then let it cool and waited. Microbes grew, and he proposed it as an example of spontaneous generation. In 1768, Lazzaro Spallanzani repeated Needham's experiment but removed all the air from the flask. No growth occurred. In 1854, Heinrich G. F. Schröder (1810–1885) and Theodor von Dusch, and in 1859, Schröder alone, repeated the Helmholtz filtration experiment and showed that living particles can be removed from air by filtering it through cotton-wool.

In 1864, Louis Pasteur finally announced the results of his scientific experiments. In a series of experiments similar to those performed earlier by Needham and Spallanzani, Pasteur demonstrated that life does not arise in areas that have not been contaminated by existing life. Pasteur's empirical results were summarized in the phrase Omne vivum ex vivo, Latin for "all life [is] from life".

After obtaining his results, Pasteur stated: "La génération spontanée est une chimère" ("Spontaneous generation is a dream").

See also

• Orthogenesis