Life as We Know It, Part 1, Lead: Thomas Davis

3/4/2002

Summary by Aaron Sommers:

Life as We Know It

This class was lead by Tom Davis, a geneticist and teacher at the University. He lead off the discussion with the question: "What is Life and would we recognize it on other worlds." The question dominated the rest of the session. Everyone present agreed that life probably exists on other planets, but how would one know it to be alive? Some ideas were brought forward in regards to "life's signature". The most popular ones were: 1) the presence of water, 2) the presence of oxygen and methane in the atmosphere. The trouble with these to points, as Tom Davis pointed out, is that they would only apply to "life as we know it." Methane and oxygen (as well as water) are crucial to organic compounds found on earth that form the building blocks of terrestrial life, but would the same be true of life elsewhere in the universe? NASA has tried to set criteria in the definition they developed: life is a self-replicating chemical process capable of undergoing the process of evolution. This opened the discussion up to the notion of what the boundary for life is. At its core, is life a DNA helix? Is a virus, basically an RNA chain needing a host to replicate, also alive? The idea that life could also be based upon inorganic compounds - or upon chemistry at all was also raised.

Tom did try to establish some guides as to how we could describe life. He stated that Life was considered to have Categories (kinds of things) and Properties (what is its nature). He also suggested that the Life Cycle is a "bio-history" that depicts the evolution of an organism. A diagram of current understanding about Life and our understanding of it is as follows:

Nothing
Quantum Flux
Everthing comes into existence
Physics
Chemistry
Elements
Molecules
Genetics
Protometabolism
"Replicators" (self replicating)
RNA world
Environment
Biology

As this model suggests, Biology (that is Life) comes late to the picture. That life would arise at all is very remote, and the fact that it exists at all is undoubtedly due to the age of the universe. By the end of this session Tom was able to introduce the concepts of Darwinian Evolution, which he elaborated upon in the next session. He started with a second diagram.

DNA Helix (Genetic Coding)
RNA Chains
Proteins - Enzymes

These are the building blocks of life, and the process of their recombination leads to the chance for mutation. This variability of inheritance is part of evolution. Sometimes these mutations give an organism an advantage in its environment. This Differential of Survival may improve the organisms, chances of reproducing, and passing on that trait to its offspring. This is what Darwin meant by "survival of the fittest."

Time ran out and Tom was left to expand upon the ideas he introduced in the next session. Everyone left, eager to delve more into the nature of "life as we know it" here on earth in our next meeting.

May 13, 2002