How Big Is Life? Lesson 80

We have already established that there was life existing at the level of a single cell, and the possibility of life, or quasi – life below the cellular level. We have established that dogs, cats, people, trees and rose bushes are all alive, and all composed of groups of cells thbat work together in concert to produce a living thing. We have also established that those living things are composed of differentiated cells, which when combined in a particular format, give us that life. It is interesting that the hundreds of different cell types -- bone, muscle, brain, heart -- all differentiate themselves from two simple original cells, the sperm and the egg. Two cells combine into one, only to later differentiate into thousands! Life it self, at the cellular level, in some respects is similar to the atom! All atoms are composed of protons and electrons. It is only the number of protons that distinguishes hydrogen gas from liquid mercury to solid aluminum!

What is it that causes something to be a live? What separates the healthy baby from the cluster of tissue which represents an early miscarriage? The baby is alive. It reacts to its environment, one learns and grows. It is a wondrous thing. However, occasionally something goes wrong in the division of the cells. What we are left with is tissue that has not formed into a human. It may have no brain. It has no thought. It may have none of the systems that we normally associate with a living being. It certainly is not human, by our definition. However, it's cellular structure may resemble any of several types of human tissue. Certainly, the individual cells may be alive at the time of birth! They have no way to sustain life after birth, so in that sense they are something like a virus. However, put into the right culture, many of these cells can multiply.

So what is it that separates living from nonliving? Sentient from non-sentient? A very interesting question.

There are two things that we should observe about living things.

First, they all come from a source. They are, if you will, born. They may be borne by cell division, they may be borne by budding, they may be borne by sexual reproduction, but a new living thing comes into being from the existence of one or more prior living things.

Second, living things metabolize. They produce energy, usually from some sort of matter. People eat food and drink water and produce energy to work and play. Withholds the food and water and the cells of the human eventually die. This is true of virtually every living thing. Now viruses and prions have no way to produce this fuel on their own. That is, perhaps, what separates them from truly living things. However, they absorb the energy of living things capable of producing it, and metabolize that energy that they receive from others.

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