Friday, August 15, 2008

Archaea, Cyanobacteria

The Archaea are considered one of the first forms of life. They were found in rocks that were judged by radiometric dating (r.d.) to be 3.5 billion years old. Traces of one of their molecules they contain (a lipid, which is a fat), were found in west Greenland and r.d. to 3.8 billion years ago. These organisms were found at extreme temperature environments at first, but since then have been found in almost any kind of environment.

Archaea were supposed at first to be variations of the bacteria, but were eventually found to be so different from bacteria that they were classified in a different kingdom, or domain, from bacteria and the other type of cell (eukaryote, or true cell). And so, it became apparent that the original organism that Darwinists look for had to be a common ancestor of both the archaea and bacteria. The search for this Last Unknown Common Ancestor, known as LUCA, is what is going on now in Origin of Life studies. Here's the rub: the fossils for the Archaea appear almost as soon as the Earth, after being bombarded by meteors, was cool enough to allow any life at all .

The cyanobacteria were formerly called bluegreen algae but now are considered bacteria. They have made hardened structures called Stromatolites which scientists use to date bacteria as far back as 2 billion years.
So, because the proteins of the prokaryotes such as cyanobacteria do not match closely to the proteins of the archaea, scientists are looking for a last previous common ancestor. They are running out of pre-organism time, because the structures of functional molecules in each of these types of organisms alone would take not millions or billions but trillions upon trillions of years to happen by chance. Any laws of physics or chemistry that would cause them to organize like the molecules I will be showing you would themselves be non-random laws (and therefore lead to a biologic anthropic principle). One study by Kaneko et al. from "DNA Research" tells us a certain strain of Cyanobacteria have 3.5 million base pairs in their DNA. It also estimates a total of over 3000 genes. The following picture shows a unit of the DNA. These units alone are hard to find in nature, much less put together in a way that is functional. They are made of atoms, such as oxygen, hydrogen, nitrogen and carbon which are arranged in a specific way. The unit on the left is the "backbone" of the DNA, the part that looks like the long sides of a ladder. The molecules on the right are attached where it says "Base" to the backbone. Each pairs to another, thus the name "base pairs" for description of DNA. A short one connects to a long one, always in the same A-T or C-G pairing. The Uracil is used in RNA instead of Thymine. These base pairs form the rungs of the ladder and make a genetic code that can be read to form proteins. The picture is from Wikipedia s.v. nucleotide. (The molecules on the right are also the components of spliceosomes I've had in recent posts).

Cyanobacteria are free-living because they have a system for photosynthesis, which allows them to convert light energy into a source for chemical energy (ATP). Kaneko et al. estimates 128 genes are needed for photosynthesis alone. The organisms can then make all the molecules they need for structure and metabolism. Their genes, made of the DNA, allow them to reproduce by themselves. The structures that have been suggested by some scientists as original life, such as ribozymes, have been manufactured in the laboratory and cannot do these necessary things, and cannot sustain themselves. One study by Ouzounis, et al. from "Research in Microbiology" has shown that at least 1000 genes are needed for life to exist independently.

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