WEIT Chap5

The Engine of Evolution

In nature we can observe the perfect adaptation of animals why ONLY animals? in their environment, [...] In order to have this result, ????

In this chapter, one important question is approached: How is natural selection linked with the adaptative behavior and how genetic interacts in the evolution.

maybe start with a general intro... Pierre.brawand 19 avril 2011 à 22:31 (CEST)

Don't say WE HAVE but maybe THERE ARE many proofs...[ [Utilisateur:Pierre.brawand|Pierre.brawand]] 19 avril 2011 à 22:31 (CEST) There are many proofs that adaptation occurs in animals why only animals???Pierre.brawand 25 mai 2011 à 22:19 (CEST). For example the woodpecker has a really strong skull and muscles that allow him to do his drumming. In his book "The Origin of species" of Charles Darwin he explained that that was "natural selection" that triggered it.

{co|Give the entire title of Drawin's book...}} Pierre.brawand 19 avril 2011 à 22:31 (CEST)
However there are problems, there are not unattackable proofs for evolution. First, evolution is extremely slow and so it is impossible to observe the new evolutions in a lifetime.
Natural selection is a process not a mechanism, it happens and it is independant from any external will.
There are three things involved in creating an adaptation by natural selection:

1)The starting population has to be variable (genetically speaking)

2)The variations must be able to be transmitted by the genes. (heritability)

3) The genetic variation must affect an individual's probability of leaving offspring

In evolution everything happens "by chance" "by accident" The filtering of that variation by natural selection produce adaptations and this is not random. The problem is that it must explain complex physiological traits.

What is the meaning of "bordelique"? I do not speak French well enough... By the way, if you could avoid writing in French, this might be good. In addition, for personal comments, use the "DISCUSSION" page instead of the "PAGE" page... ;-)Pierre.brawand 19 avril 2011 à 22:31 (CEST)

Evolution without selection

Genetic drift is a process which happens randomly and usually in a small population or even in just a few immigrants which colonize a new area. It can change the frequencies of alleles regardless of their usefulness for its carrier. One gene can be even fixed or complitely lost. For example, there is a drastic reduction of the population, called population bottleneck.

not a good definition }Pierre.brawand 25 mai 2011 à 22:19 (CEST). It is a random fact that in a probalistic situation that an outcome comes more often than the other

not clear enough[ [ Utilisateur:Pierre.brawand|Pierre.brawand]] 19 avril 2011 à 22:33 (CEST): 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.)(cf. p.122)
difference between Nat selec and gen drift
Natural selection will select only the useful feature s {{co|are you sure that the term USEFUL is the right one?} }[[U tilisateur:Pierre.brawand|Pierre.brawand]] 19 avril 2011 à 22:33 (CEST) 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")

{{co|not clear enough} }[[Ut ilisateur:Pierre.brawand|Pierre.brawand]] 19 avril 2011 à 22:33 (CEST)

Animal and plant breeding

Artificial selection: Humans 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, humans have "created" new domestic dog races derived from the original wolf in how many years?Pierre.brawand 29 mai 2011 à 22:03 (CEST). 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 natural selection and artificial selection
In artificial selection this is the breeder rather than the nature who sorts 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."

OK for the general idea. Couls you maybe make links between the different sentences and ideas?Pierre.brawand 29 mai 2011 à 22:03 (CEST)

Evolution is the test tube

There is a way to see proofs of evolution in laboratory. Indeed, we can observe some adaptations by challenging a captive population with a new environment. Even if the environmental changes are caused by humans, it is still a natural selection that occurs, because humans don't control the reproduction of the organisms.

The easiest and clearest way to experiment it is to use microbes, because they reproduce very quickly and we can see thousand of generations pass over in twenty minutes ! And indeed, microbes adapt themselves to any situation : starvation, temperature changes, viruses, and so on...

The main aim of this experiment is to show that new traits are not created out of nowhere, but they are the result of modification of old features.

Resistance to drugs and poisons

Drugs can heal infectious diseases, but natural selection has to be taken into account. Indeed, as there are enormous population sizes and short generations, there are greater chances for mutations, which produce antibiotic resistance, to occur.

The bacteria that become resistant to these drugs because of mutations, are those which survive. Eventually, the drugs won't be effective anymore.

This is one of the best example of natural selection, for the drug resistance doesn't occur because of changes in the patient, but because the microbes evolve.

This is of course not the case for all microorganisms: sometimes mutations don't arise, and there is no evolution.

Thanks to natural selection, some species adapted themselves to changes that have been caused by humans (like the insects that have become resistant to DDT- an insecticide).

Selection in the wild

In some cases, even if the changes have been caused by humans, the response is natural. But it would be even more convincing to see the process of natural selection in action and without any human intervention. However, this process in the wild is most of the time really slow.

The only way to see it would be in species that have short generation times, so that evolution can be observed over several generations. This evolution has to be caused by a strong selection, causing rapid changes.

A macroevolution (selection that transforms an animal into another, for example) is impossible to see in a human lifetime, even if it is happening now.

All we can see are microevolutionary changes.

However, we must not forget that species already have evolved to be adapted to their environment. Even if there are no environmental challenges, stabilizing selection is occurring. This kind of selection doesn't create new features, but will for example cause the elimination of genes that aren't useful for the organism.

Can selection build complexity?

If you let time the natural selection can build big things because we have seen that artificial selection has changed things.
We will never be able to reconstruct how selection created everything, some things will always be unknown due to lack of data and to the huge amount of information that we should know.
"What is the alternative theory? Creationism." Some people are not convinced by this theory because we don't know everything.

expliquez mieux ce que c'est la complexity

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 =
macroevolution = transforming one "type" of plant by evolution.
microevolution = small changes in one or a few features of a species.
stabilizing selection = when an animal is perfectly adapted the only evolution which is happenning is the stabilizing selection, it will approach itself to the golden mean.

good start... It's been a long day... time to rest!!!Pierre.brawand 19 avril 2011 à 22:35 (CEST)

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