Part III: Evolution and Speciation- Take 2

Evolution Review

Remember that evolution is an excellent example of the Flow of information, in this case the flow of genetic information. When we learned about mitosis, meiosis and inheritance we examined the flow of genetic information from one cell to the next and from one parent to child/offspring.

But those parents and children live in a population surrounded by  other members of their species. And the flow of genetic information from one parent to one child is also happening to the other parents and children. And depending on the environment in which they find themselves, there are patterns to that flow of information from one generation of the population to the next generation of the population. All the alleles in all the individuals in that population is called the gene pool.

And any patterns or changes to that gene pool (of the population) is called evolution. 

Evolution: Short Term vs. Long Term Consequences

Shorter Time Scale: Adaptations 

Evolution can be caused by different mechanisms, but when it is caused by natural selection, then the result is an adaptation.  This does take many generations to occur, but relative to the time scale of the earth's  history, this is a short term consequence.

But if two populations of the same species are living in different locations with different environmental conditions, then the alleles that are beneficial in one population will not be the alleles that are beneficial in the other population.  

Longer Time Scale: Speciation 

This means that the evolution (change in the gene pool)  of these populations will begin to diverge. If there are enough differences in these two gene pools then 

1st    reproductive barriers develop between the populations

2nd   the two populations' gene pools will diverge more and more 

3rd   with enough difference they become two different species

A species is defined as a group of individuals who can mate with each other and produce offspring that are fertile. 

This video does a good job of outlining these issues.