Throughout time, humankind has pondered questions of life and death. As man's scientific wit has grown sharper, the life questions have become more focused and defined: Biologically speaking, exactly what is “life”? When, where, and how did this life force appear on this planet? When does an individual organism become living? How does life at the individual cell level translate into life at the organismal level? Conversely, what is “death” biologically speaking? When an organism dies what happens to its life force?
These are legitimate questions that impact each person in one way or another on any number of different levels – biologically, medically, socially, philosophically, and religiously. Unfortunately (or fortunately depending on one's faith in humankind to properly handle such monumentally important knowledge) at the present time there are no definitive answers for any of these questions.
The Properties of Life
While most questions dealing with the biological nature of life still cannot be answered, science does know that all living organisms, regardless of their complexity (or the lack thereof), share a set of basic characteristics or properties. These commonly-held life properties should be regarded as the signs of life rather than the definition of life.
1. Biogenesis. Any organism originates from an organism (asexual) or organisms (sexual) of the same species. Living things do not spontaneously spring into life.
2. Organization. All organisms are composed of one or more cells and these cells are constructed of the same basic types of atoms and molecules.
3. Sensitivity. All organisms respond to internal and external stimuli (signals).
4. Metabolism. All organisms require energy (food) and produce waste products. Food energy is used to maintain internal order and to grow (add new cells).
5.Homeostasis. All organisms maintain stable internal conditions that are different than the surrounding environment.
6. Movement. All organisms are capable of self-generated movement at some scale and at some stage of their life cycle.
7. Reproduction. All organisms are capable of reproduction.
8. Life Stages. All organisms grow and develop through definite stages – beginning, growth, maturity, decline, and death.
The Possibility of Synthetic Life
Will biologists ever be able to actually create a living cell(s) from inorganic chemicals? Is it possible to create an artificial life form? While this sounds like science fiction or even a Biblical miracle, science may actually be inching ever closer to doing exactly that and the promises of a new branch of biology known as synthetic biology may hold the key.
The question at this point seems not to be, “Will humans ever create life from scratch?” but simply how much creating the life would cost. There is the belief among some that the number of steps that might be real potential roadblocks to such an undertaking has declined almost to zero. In fact, some researchers optimistically suggest that for less than a third of the approximately $500 million dollars spent to sequence (map) the human genome, it is conceivable that organic chemicals could be transformed into a single – celled organism that would grow, divide, and evolve and that such an amazing and profound feat could be accomplished in 3 to 5 years time.
Armed with only a few basic types of living building blocks known as cells, evolution has managed to fashion millions to perhaps tens of millions of different types of creatures – plants, animals, and microbes – that occupy every nook and cranny of this place. As a result, humans are blessed to live on a planet bubbling and swarming with a riotous multitude of life forms. To gaze upon it and to contemplate the beauty, mystery, and wonder of it all is to be filled with awe and reverence.
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