Biogenesis
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Biogenesis is the process of lifeforms producing other lifeforms, e.g. a spider lays eggs, which develop into spiders. It may also refer to biochemical processes of production in living organisms.
Generatio spontanea
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.
Francesco Redi, an Italian physician, proved as early as 1668 that higher forms of life did not originate spontaneously, but proponents of abiogenesis 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 1800s 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.[1]
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 today 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 ovo, Latin for all life [is] from eggs.[2][3]
Law of Biogenesis
The Law of Biogenesis, attributed to Louis Pasteur, states that life forms such as mice, maggots, and bacteria cannot appear fully formed. The law says nothing, however, about the biogenesis of very primitive life from increasingly complex molecules.
It is often cited by Creationists and Intelligent Design proponents as evidence for the need of an intelligent Creator or Designer. They describe the law of biogenesis as stating that life cannot come from non-life, it can only come from other life.
Orthogenesis
A second meaning of biogenesis was given by the French Jesuit priest, scientist and philosopher Pierre Teilhard de Chardin to mean the origin of life itself due to an inherent drive of matter towards higher consciousness, an extension of the orthogenesis hypothesis.