PDA

View Full Version : Astrobiology question



ESAssi
2011-Jan-02, 09:49 AM
Hi!
I'm working on a project and need help with a question that I need to answer. I would really appreciate what you have to say about this...

Question: How does artificial selection by human agricultural industries differ from natural selection? Going back to Darwin’s books, did he rely mostly on field observations of natural ecosystems or on artificial selection to make his arguments? :think:

JohnD
2011-Jan-02, 12:41 PM
ESAssi,
It doesn't differ.
Why/how should it?

Except that the use of insecticides, or even antibiotics, exrt a much greater selection pressure than any previously seen in nature.
Resistance to DDT or to, say, penicillen, has arisen in about fifty years after they were introduced.

OR, do you mean selection of traits in plants and animals for commercial or fancy reasons? The original potato was a puny tuber compared to King Edward, and budgerigars that were native and exclusive to Australia now have many different 'breeds', all due to selection by breeders. Not as in Darwinian evolution by the illfavoured traits leading to an early death, but by the breeders only permitting those that carry favoured traits to mate and have offspring. So, mechanism the same, mate or not, but for different reasons.

Many dog breeds, 'created' exclusively by dog breeders, are so disadvantaged that they could not survive in the wild. All dogs are still the same species, but the extreme variation in their shapes just proves Darwin was right, as even unnatural evolution pressures trend towards the "Origin of Species"!

John

slang
2011-Jan-02, 12:44 PM
Hi ESAssi, welcome to BAUT.

Is this a homework question? There are at least two differences between the two forms of selection that I can think of, and they seem fairly obvious. They are to do with the factor time, and the type of traits that are selected for.

ETA: and how does this relate to astrobiology?

caveman1917
2011-Jan-02, 02:51 PM
There is no difference whatsoever.

Think about some plant species which need the intervention of bees to propagate. The bees will exert evolutionary pressure on certain aspects of those plants (for example how much nectar it produces), and only those that are deemed 'good' by the bees will be allowed to breed. How does this differ from human agricultural practices?

The pressure exerted by humans is natural selection, the term 'artificial selection' is a misnomer and highly misleading - as if it were anything different from 'natural selection'. We are as much a part of the natural environment plants find themselves in as any other animal species.

ETA: Darwin mainly used field observations.

Centaur
2011-Jan-02, 04:34 PM
The pressure exerted by humans is natural selection, the term 'artificial selection' is a misnomer and highly misleading - as if it were anything different from 'natural selection'. We are as much a part of the natural environment plants find themselves in as any other animal species.


I understand the point you are trying to make, but the word artificial has no meaning if we say that anything done by humans is natural. Granted, in the overall scheme of things humans are part of the natural world. But in the context to which the OP was referring, we can understand how the word natural would exclude that which is artificial.

caveman1917
2011-Jan-02, 05:09 PM
I understand the point you are trying to make, but the word artificial has no meaning if we say that anything done by humans is natural. Granted, in the overall scheme of things humans are part of the natural world. But in the context to which the OP was referring, we can understand how the word natural would exclude that which is artificial.

In a sense you are correct of course. I was just trying to warn against the possible misconception that there is any real difference between natural selection and artificial selection. The last question by the OP (wether Darwin used field observations or artificial selection to make his arguments) lit up an alarm light concerning that, as if the conclusions would have been any different had he used the other one. Perhaps the OP question can be answered by a one word response: anthropocentrism :)

Swift
2011-Jan-02, 08:01 PM
Going back to Darwin’s books, did he rely mostly on field observations of natural ecosystems or on artificial selection to make his arguments? :think:

ETA: Darwin mainly used field observations.
My understanding is he used both among his arguments for evolution. I think there were relatively more based on natural ecosystems, but he did use both.

I found this PDF slideshow on line (http://patrick.maher1.net/318/lectures/darwin1.pdf) that discusses some of the arguments.

Oh, and welcome to BAUT ESAssi

TheNightowl
2011-Jan-03, 06:26 AM
If I understand the question, I believe that human-directed selection differs from natural selection in that it does not select for survivability characteristics, in fact, sometimes going so far as to select for traits resulting in nonviability without continued human intervention. Natural selection says that species best adapted to survive in their environment thrive and have higher reproductive rates. Humans create "seedless" fruits and vegetables, and deliberately breed sterile animals like mules, which might occur naturally but in much smaller numbers and cannot reproduce on their own.

Nightowl

JCoyote
2011-Jan-03, 07:08 PM
Natural selection weeds out organisms in favor of general survivability, human directed selection however weeds out organisms in favor of specifically symbiotic traits. Arguably ants that herd aphids have brought about some level of similar selection in those cases. Species partnerships like this means natural selection applies to both species along related lines.

JohnD
2011-Jan-03, 09:07 PM
To reinforce the idea, Darwin was the naturalist, who mainly observed, minutely and on a macroscopic scale too.
His great idea did not include any mechanism for passing on the mutations that he supposed happened, whihc was a gap in the theory.

But Mendel was the scientist. He knew of Darwins work, when Darwin did not of his; few people did. He proposed the gene, and the way that genes work. He was the manipulator, who artificially selected his pea plants to first observe the effects and then demonstrate his theories.

JOhn

ESAssi
2011-Jan-05, 02:22 PM
THANK you guys! Helped me a lot :clap:

caveman1917
2011-Jan-05, 07:11 PM
If I understand the question, I believe that human-directed selection differs from natural selection in that it does not select for survivability characteristics

But it does select for survivability characteristics, by definition. The 'survivability' of an organism is always something relative to the real local environment, not some hypothetical different environment.


, in fact, sometimes going so far as to select for traits resulting in nonviability without continued human intervention.

But so do the bees, as well as countless other examples. I don't think we'd claim these are also different from natural selection because it doesn't select for traits useful in a hypothetical environment without bees. It just seems a bit akin to stating the evolution of a polar bear is not natural because it doesn't select for survivability in a jungle.


Natural selection says that species best adapted to survive in their environment thrive and have higher reproductive rates.

Not necessarily. And selection applies mostly intraspecies, between individuals - between genes even. It just states that those genes whos phenotypic expression increases survivability (relative to the concrete environment) will more likely continue to exist in individuals in the next generation. It might as well be with a lower reproductive rate if the individual itself is more resilient.

caveman1917
2011-Jan-05, 07:29 PM
Natural selection weeds out organisms in favor of general survivability, human directed selection however weeds out organisms in favor of specifically symbiotic traits.

Not general survivability, specific survivability relative to the real environmental pressures that exist on the specific individual. Sure we might imagine an environment for those organisms where they are then not as well adapted to, but evolution is a purely local law. It is completely agnostic on the existence of other environments, they're just not relevant, like the polar bear and the jungle.

I find it a bit surprising we seem to be so unable to realise that we just can't abstract ourselves out of the environment. We might say it is 'artificial' because 'we did it' (though i would question the scientific validity of such distinction, it seems more to just arise out of a need for us to feel 'special' relative to other species), but there is no real difference here.

Every distinction offered so far seems to be unaware that most other animal species do the exact same thing as that which is said to be specific to 'artificial selection'.

WayneFrancis
2011-Jan-06, 05:29 AM
Hi!
I'm working on a project and need help with a question that I need to answer. I would really appreciate what you have to say about this...

Question: How does artificial selection by human agricultural industries differ from natural selection? Going back to Darwin’s books, did he rely mostly on field observations of natural ecosystems or on artificial selection to make his arguments? :think:

Your question is similar to "What is the difference between macro and micro evolution" realistically just scale and, as almost always is the case in biology, there is no dividing line between black and white just a whole bunch of grey.

Artificial selection is only useful as a term to group selection pressure that are directly controlled by us. End of the day the process is the same.