Evolution in a few hundred words

Today I'm going to give some explanations to the mechanisms of evolution I described yesterday. These examples come adapted from the same textbook as I used yesterday.


I thought I might break them up into 2 categories as well, to make things a bit more simpler.


Processes that introduce new genes/alleles into a population:

• Mutations
• Basically the source of all new genes and alleles in any given population
• This occurs when part of the base code of DNA changes from one form to another, or rearranges itself somehow (I've included a picture of this at the bottom - Figure 1)
• Genes are small "coding" sections of DNA, so when these mutations occur within a gene, it may change its expression

• Migration
• Migration is movement of of individuals from subpopulations within a larger population
• This means that new genes that have developed in one subpopulation can be transferred to another through mating
• For example, say you have a population of black birds, and another population with yellow birds and black birds in it. A yellow bird from the second population may fly over to the first population of entirely black birds and breed. This could then introduce the yellow colouring into the other population

Processes that affect allele and gene frequency within populations and drive evolution:

• Natural Selection
• Most simply put - survival of the fittest
• Those with the best genes to suit the environment will obviously survive better in that environment and will be able to reproduce more successfully
• If the environment changes, different genes may be more useful and therefore different organisms will flourish
• The best example of this is the peppered moth. Before the industrial revolution, light coloured peppered moths were higher in population than black coloured moths. This was because they camouflaged on trees better, and weren't eaten as often. As industry took hold and factories started producing, the trees became covered in soot. Now the light coloured moths stood out much clearer on the trees, while the black coloured moths camouflaged. Following this, the black moths rose in number, and the light ones fell because the black were more suited to the new environment
• New species can be made through natural selection when an event (or even migration) separates a population and applies different environmental pressures to them. The populations adapt differently to their different environments, and over time become two different species

• Genetic Drift
• Genetic drift is the random inheritance of genes and alleles passed through generations
• This random chance of inheritance changes the frequency that alleles appear
• As I couldn't get the animation work in the blog, here is a link that explains genetic drift quite well (again with wiki... but is just a picture that is effective at explaining what is happening) 
• So even if parents are selected by natural selection, genetic drift may cause the offspring to fail in the environment

Sorry for the epically big blog post, but I really wanted to get all that out. If any of it is unclear or you need more info, post comments and ask!

Figure 1: Some types of mutations shown here as examples. Sourced from Wikipedia.