When Simple Is Not So Simple

The theory of chemical evolution proposes that life on earth developed by spontaneous chemical reaction billions of years ago.

This theory is not that an accident directly transformed lifeless matter into birds, reptiles, or other complex lifeforms. Rather, the claim is that  a series of spontaneous chemical reactions eventually resulted in very simple lifeforms such as algae and other single-celled organisms. 

Based on what is now known about these single-celled organisms,m is it reasonable to assume that they are  so simple that they could have appeared spontaneously?  For example, how simple are single-celled algae?  Let's examine one type in particular, the unicellular green algae of the genus Dunaliella of the order Volvocales. 

Unique Single-Celled Organisms

The Dunaliella cells are ovoid, or egg-shaped, and very small-about ten microns long. Placed end to end, it would take about 2,500 of them to make one inch. Each cell has two whip-like flagella at one end, which allow it to swim. Similar to plants, Dunaliella cells use photosynthesis to provide energy.  The produce food from carbon dioxide, minerals, and other nutrients  absorbed into the cell, and they reproduce by cell division. 

Dunaliella can live even in a saturated salt solution. It is one of the very few organisms of any kind that can live and propagate in the Dead Sea, which has a salt concentration about eight times that of seawater.  This so-called simple organism can also survive sudden changes in the salt concentration of its environment.

 Consider, for instance, Dunaliella bardawill, found in shallow salt marshes in the Sinai desert.  The water in these marshes can be diluted quickly during a thunderstorm or can reach saturated salt concentration when the extreme desert heats the evaporated water. Thanks in part to its ability to produce and accumulate glycerol in just the right amount, this tiny alga can tolerate such extreme changes.  Dunaliella garawil is able to synthesize glycerol very rapidly, starting within minutes of a change in salt concentration, either producing or eliminating glycerol as needed in order to adapt. This is important  because in some habitats that salt concentration  can change considerably  within a matter of hours.  

Next time: When Simple Is Not So Simple/Conclusion of Unique Single-Celled Organisms

From the Awake! magazine