WEIT Chap5

The Engine of Evolution

Structure of the chapter

The engine of evolution

evolution without selection
Genetic drift: Helps natural selection to build evolution. It is a random fact that in a probalistic situation that an outcome comes more often than the other: For example in a F1 generation one parent having a AB (one A and one B allele) blood type, if the parent has only 1 child it will transmit only one of the two alleles and the other one would be lost. (the parent could have 4 children and the same problem, always randomly give one of the two alleles.)
difference between Nat selec and gen drift
Natural selection will select only the useful features whereas the genetic drift is random and can generate useful or harmful changes. Genetic drift happens because there are only limited amount of offsprings (the ideal probability will thus not be respected since there are not an infinity of them. It is impossible to reach an ideal probability as we seen in maths when there are not an infinite of "tries")

animal and plant breeding
artificial selection: the human can choose for a given species which individuals are to reproduce and thereby enhance a particular feature from the two previous genetic material (cf. ETIVAZ documentary on cows seen in class) Thanks to this process men has "created" new domestic dog races from the original wolf. This selection has been done really quickly so we can think that natural selection takes more time and tries and can build much more diversity.

difference between nat selec and artif selec.
In artificial selection this is the breeder rather than the nature who sort out which variants are good or bad. In other words, the criterion of reproductive success is human desire rather than adaptation to a natural environment.

Proof that natural selection occurs and evolution is true because we can observe it. IT is now easier to accept natural evolution since we have seen that artificial selection happens."

evolution is the test tube
Try to show what happens in nature by observing it in laboratory. We change for exeemple the environment of a given organisme let's say bacterias. We change their environment in order to see how they can adapt themselves and how selection occurs. Bacterias are good because a new generation is done every 20min and it is easier in a lifetime to observe changes.

resistance to drugs and poisons
Viruses. The big problem is that the virus adapt themselves to the new environment of antibiotics according to natural selection. The weak ones are killed and only the resistant ones develop.(this is why each year the flu vaccin changes.)
Fortunately not all pathogens don't adapt to treatments for example measles didn't manage to evolve and to develop a resistance to the new vaccine.

selection in the wild
Selection in nature is really slow to happen. That's why it is hard to believe for some people.
can selection build complexity (Popo)

Vocabulary List

artificial selection =
random = regardless of wether it is useful to the individual
heritability = the genetic basis of a variation
process = a description of how genes that produce better adaptation become more frequent over time, without external will.
mechanism = a process imposed on a population from the outside
fitness = average number of offspring
mutation =
neutral variation = a variation which is neither good or bad
environment =

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