Biological adaptation

Organisms rarely live in a constant environment.  They often experience times of feast and times of famine, changing numbers of predators, prey and pathogens, changing physical and chemical conditions.  To put it simply, changing threats and opportunities.  

The very processes that underlie the maintenance and growth of life changes the environment – energy must be captured and transformed for life to continue. 

Nutrients present in the organism's immediate environment are used up, waste products released and may accumulate.  One organism's waste can become another's food or poison.

To survive, organisms need to be able to adapt to changes in its environment. 

Take yourself as an example, when the temperature rises you sweat and you might  decide to remove some clothes; when the temperature drops you shiver and perhaps put on clothes - both the these are adaptive responses.  One type is physiological (sweating and shivering) – such responses are generally unconscious, you do not decide to shiver, your body does.  The other is behavioral (putting on and taking off clothing) and requires conscious thought.   

There are also slower types of physiological adaptation, such as the ability of certain animals to grow thick and more insulating fur or the shedding of such fur in preparation for and response to the predictable changes in weather associated with the changing seasons. 

Both physiological and behavior types of adaptation are the result of evolutionary processes.   Mutations of various sorts, including gene and genome duplications, together with selective processes enable a population of organisms to adopt specific life styles.  These evolutionary processes occur over a large number of generations.  

Rapid (seconds to minutes) adaptive responses depend primarily upon changes in the activity of proteins, slower responses (minutes to hours, days, and months) generally begin with changes in protein activity, but then involve changes in gene expression.   The network laboratory (in preparation) will introduce you how such adaptive processes occur. 

Both types of adaptive behavior are traits/abilities that enable a species to survive and reproduce effectively in a specific niche. 

Bacteria and the study of adaptation: 

Bacteria make a good system in which to study the process of adaptation in large part because they can, under the right conditions, grow very rapidly (something that is explored in great detail in the growth laboratory. 

We can easily grow up cultures of genetically identical organisms within a few hours, and we can examine evolutionary behavior over many thousands of generations.  

We will model some of our studies on experiments of this type carried out Richard Lenski and others. 

Another aspect of bacteria is that even though they are relatively simple organisms, they also display a range of complex behaviors.   These include swimming toward nutrients and away from noxious chemicals (chemotaxis), and the ability to communicate with one another (quorum sensing). 

Moreover, even though genetically identical, two bacterial cells can behave differently under the same conditions.   

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