The Miller Urey experiment helped show how it was possible to derive some of the components of life from isolated molecules.
In the 1950's, biochemists Stanley Miller and Harold Urey, conducted an
experiment which demonstrated that some of the basic elements of life,
including amino acids, could be formed spontaneously by simulating the
conditions of Earth's early atmosphere. The presence of an ocean was
important to help preserve the forming molecules in a quiet, stable
environment. Their experiments lent support to the theory that the first
life forms arose spontaneous ly through naturally occuring chemical
reactions. In whatever way that life on Earth came to be, by 3.8 BYA, the
middle of the Archean age, (very early in the history of the Earth!), life
on Earth included both early autotrophs and early heterotrophs.
Organisms that are able to make their own food (in the form of sugars)
by using the energy of the Sun are called autotrophs, meaning
"self-feeders". Photosynthesis is the name of the process by which these
autotrophs eat. Organisms which require food from sources outside
themselves; other organic matter, or other chemical syn thesis of food,
are called heterotrophs, meaning "other-feeders". Because the autotrophic
bacteria were able to feed themselves by using the energy of the Sun, they
were not dependent on the same limited food supply as their heterotrophic
contemporaries and were able to flourish.
The appearance of these organisms capable of performing photosynthesis was of
monumental significance -- if it weren't for the photosynthetic activity of
these early bacteria, Earth's atmosphere would still be without oxygen
and the appearance of oxygen-dependent animals, including humans, would
never have occurred!
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