The Essentials: Evolving Under Our Nose

While Crichton’s bacterial population boom is an unsettling thought the idea of limits to the populations growth is even more problematic.  As discussed previously the population of bacteria will inevitably face limits and with these limits will come competition.  The individuals most fit to survive will pass on their genes to the next generation and the next generation of bacteria will consequently be more like the survivors.  The selection pressures will effectively shape the appearance of the population over time. In other words the population will change, or evolve. 

Antibiotics are a strong selective pressure on populations of bacteria. These powerful drugs target bacteria for destruction in order to get us healthy when we are sick. However the populations of bacteria that make us sick have variety in their individuals and some of these individuals are more resistant to the effects of the antibiotics. These antibiotic resistant bacteria are the survivors in the population and over time the population will be comprised of all resistant individuals.  In just a few days the population can have a very different composition.

This is evolution and it happens all of the time.  In a few days bacteria can show us how the mechanism of natural selection works and gives us a glimpse of how it has been playing out for the last several million years.