What Exactly Is Natural Selection? (1 Viewer)

[Trebla]

Hi, I need confirmation on the definition of natural selection. The definition I have at the moment (quoted from Jacaranda) is the process in which agents of selection act differentially and with no human intervention on various phenotypes in members of a population.
However, in many books, the modern examples (I'm answering 9.3.4 2nd column d.p.4) given for natural selection were often a result of human intervention on the surrounding environment.
For example the peppered moth in Britain, where pollution from increased industrialisation enhanced the survival of the black peppered moths over time and degraded the white pepper moths, through ability to camouflage due to soot deposits, is given as a modern example of natural selection although human intervention is seen through pollution.
So, I would like to ask:
Can natural selection also be a result of unintended factors of mankind such as pollution or does it have to be result of natural factors only?
Also, if possible can someone give me another modern example (preferrably Australian) of natural selection?

Thanks

 

[Not-That-Bright]

Can natural selection also be a result of unintended factors of mankind such as pollution or does it have to be result of natural factors only?
Also, if possible can someone give me another modern example (preferrably Australian) of natural selection?

While of course we cannot give a modern example of macro evolution, we can give modern examples of natural selection without the aid of humans... what is usually meant by no human intervention is that humans have not selectively bred the animals, but that they changed naturally due to the environment. The peppered moth is still a great example, however for an Australian example I have none of the top of my head from modern times.

Of course, one of the reasons why most examples will result from human changes to the environment... is probably because our changes have been particularily rapid requiring much faster levels of evolution - Whereas other changes in the environment have been much slower.

 

[Trebla]

So human intervention is meant to be the direct interference on the nature of evolution such as selective breeding, but is not also meant to be the indirect impact on evolution such as pollution/changes in the environment.....right?

 

[Not-That-Bright]

Yea I'm pretty sure that's what they mean... by the way natural selection isn't about 'random'.

The genetic variation that occurs in a population because of mutation is random-but selection acts on that variation in a very non-random way: genetic variants that aid survival and reproduction are much more likely to become common than variants that don't. Natural selection is NOT random!

 

[Trebla]

OK thanks a lot...

 

[melimoo]

variation : pressure : selection : survival : reproduction
5 words that will save you in any natural selection question.
in any species there is variation (mutations etc). some kind of pressure is put on the species benefiting those individuals with the variation. therefore they are 'selected' and the others die or whatever. these individuals are able to survive in their new situation (ie with the new pressure) and then they reproduce to make happy babies with their advantageous variation

 

[melimoo]

lol, after reading your post:
natural selection occurs with any change in the environment. be it human or natural. natural selection doesn't stop and go "hey, wait up. we can't do this thang because those dang human are making this mess" species are forced to adapt.
and i forget which example of natural selection i used. i think i used mostly darwin's finches. some people had a few qualms i remember about using the peppered moth as a valid example but i still think its ok.

 

[Master Gopher]

The peppered moth is a perfectly valid example!

Natural selection really has nothing to do with the *type* of pressures being put on a population. It has more to do with how the population changes, i.e. that less fit individuals die out and more fit individuals survive to reproduce. The "natural" in natural selection refers to the fact that this is totally random and not controlled by some sort of law other than that (in the words of Douglas Adams) "That which survives, survives". It doesn't matter whether the source of pressure is man-made (pollution, habitat loss, introduced species, etc) or natural (normal climate change, movement of continental plates, disease etc).

The confusion that arises is basically about selective breeding. This is NOT natural selection - because it is not natural. The breeder is selecting specific characteristics that they want - not just because they will make the organism survive better. For example, they might only like black dogs, so they keep breeding only from black ones. This has little to do with adaptation to environment.

To summarise: Natural selection can be caused by any sort of pressure, human or otherwise, but must involve continued survival of the fittest simply because those organisms fare better, not continued survival of the characteristics selected by some conscious entity like a breeder. That is artifical selection.

Hope that helps

 

[georgechah1]

Natural Slection is somthing close to the survival of the fittest, whereas the most well-dapted and the stronguest survive and pass on their genes/characteristics to the next generation.

 

[sparkl3z]

natural selection survival of the fittest etc....all related to the environment, the environment change/s or change/s within the species of a group of animals.
so, the population that is best adapted to that environment survives....i'll give an example in more simple terms.
lets say we have birds, two types, one that eats vegetables, one that eats meat (hypothetically).....say something happened (drought or bushfire...anything) and all the vegetables dried out, and there were mostly animals left, no veggies... this means the vegetable eating birds are less likely to survive, the meat eating birds mate, and multiply their numbers, making them more likely to take over, aka natural selection.

 

[Survivor39]

natural selection survival of the fittest etc....all related to the environment, the environment change/s or change/s within the species of a group of animals.
so, the population that is best adapted to that environment survives....i'll give an example in more simple terms.
lets say we have birds, two types, one that eats vegetables, one that eats meat (hypothetically).....say something happened (drought or bushfire...anything) and all the vegetables dried out, and there were mostly animals left, no veggies... this means the vegetable eating birds are less likely to survive, the meat eating birds mate, and multiply their numbers, making them more likely to take over, aka natural selection.

That's correct. Natural selection can also take form within ONE population, as oppose to the example given by sparkl3z (in different populations). Some individual in one population might have a selective advantage over the others which enable it to pass on its offspring.