Conservapedia - User contributions [en]

Newton's Laws of Motion

2007-07-06T14:58:13Z

Elevens:

[[Isaac Newton]]'s 3 laws of motion form the basis for [[classical mechanics]]. They are:

1) An object in motion will remain in motion unless acted upon by an outside force. An object at rest will remain at rest unless acted upon by an outside force.

2) The rate of change of an object's [[momentum]] is equal to the net force acting on it (<math>F = dp/dt </math>, sometimes written as <math>F = m*a</math>).

3) For every action there is an equal and opposite reaction; or, more precisely, the total momentum of any isolated system is always constant.

==Explanation==

The first law defines an [[inertial]] [[frame of reference]] as one which is acted upon by no outside forces. In general, inertial frames are far easier to understand conceptually and deal with mathematically than accelerated frames.

The second law relates force and [[momentum]]. Mathematically, <math>F = dp/dt = d(m*v)/dt = m*dv/dt + v*dm/dt</math>. Usually <math>dm/dt=0</math>, so the law is simplified to <math>F = m*dv/dt = m*a</math>, or mass times acceleration. A notable exception is [[rocket]] motion, where <math>dm/dt</math> is not 0, and so <math>F = m*a</math> does not apply. Note that the quantities '''F''', '''p''', '''v''', and '''a''' are all [[vector]] quantities--that is, they have an associated direction as well as a magnitude. In general, the second law gives a way to predict the motion of an object by summing all the forces acting on that object.

The third law states that momentum is always conserved. If one object imparts a momentum p0 on another, the first object's momentum will change by -p0. This can be viewed as a consequence of [[Noether's Theorem]]; the associated [[symmetry]] is that the laws of physics do not change under spatial translations (that is, the laws of physics are the same everywhere).

Newton's Laws of Motion

2007-07-06T14:55:44Z

Elevens:

Newton's Laws of Motion

2007-07-06T14:52:41Z

Elevens:

[[Isaac Newton]]'s 3 laws of motion form the basis for [[classical mechanics]]. They are:

1) An object in motion will remain in motion unless acted upon by an outside force. An object at rest will remain at rest unless acted upon by an outside force.

2) The rate of change of an object's [[momentum]] is equal to the net force acting on it (<math>F = dp/dt </math>, sometimes written as <math>F = m*a</math>).

3) For every action there is an equal and opposite reaction; or, more precisely, the total momentum of any isolated system is always constant.

==Explanation==

The first law defines an [[inertial]] [[frame of reference]] as one which is acted upon by no outside forces. In general, inertial frames are far easier to understand conceptually and deal with mathematically than accelerated frames.

The second law relates force and [[momentum]]. Mathematically, <math>F = dp/dt = d(m*v)/dt = m*dv/dt + v*dm/dt</math>. Usually '''dm/dt=0''', so the law is simplified to '''F = m*dv/dt = m*a''', or mass times acceleration. A notable exception is [[rocket]] motion, where '''dm/dt''' is not 0, and so '''F = m*a''' does not apply. Note that the quantities '''F''', '''p''', '''v''', and '''a''' are all [[vector]] quantities--that is, they have an associated direction as well as a magnitude. In general, the second law gives a way to predict the motion of an object by summing all the forces acting on that object.

The third law states that momentum is always conserved. If one object imparts a momentum p0 on another, the first object's momentum will change by -p0.

Newton's Laws of Motion

2007-07-06T14:51:37Z

Elevens: New page: Isaac Newton's 3 laws of motion form the basis for classical mechanics. They are: 1) An object in motion will remain in motion unless acted upon by an outside force. An object a...

[[Isaac Newton]]'s 3 laws of motion form the basis for [[classical mechanics]]. They are:

1) An object in motion will remain in motion unless acted upon by an outside force. An object at rest will remain at rest unless acted upon by an outside force.

2) The rate of change of an object's [[momentum]] is equal to the net force acting on it (<math>F = dp/dt </math>, sometimes written as '''F = m*a''').

3) For every action there is an equal and opposite reaction; or, more precisely, the total momentum of any isolated system is always constant.

==Explanation==

The first law defines an [[inertial]] [[frame of reference]] as one which is acted upon by no outside forces. In general, inertial frames are far easier to understand conceptually and deal with mathematically than accelerated frames.

The second law relates force and [[momentum]]. Mathematically, '''F = dp/dt = d(m*v)/dt = m*dv/dt + v*dm/dt'''. Usually '''dm/dt=0''', so the law is simplified to '''F = m*dv/dt = m*a''', or mass times acceleration. A notable exception is [[rocket]] motion, where '''dm/dt''' is not 0, and so '''F = m*a''' does not apply. Note that the quantities '''F''', '''p''', '''v''', and '''a''' are all [[vector]] quantities--that is, they have an associated direction as well as a magnitude. In general, the second law gives a way to predict the motion of an object by summing all the forces acting on that object.

The third law states that momentum is always conserved. If one object imparts a momentum p0 on another, the first object's momentum will change by -p0.

Natural selection

2007-07-06T04:52:04Z

Elevens: Clarified the peacock's tail (a long tail helps more than it hurts), and added a bit more to the locality section

The fundamental statement of '''natural selection''' is that heritable traits which are beneficial will become more numerous in successive generations, while heritable traits which are harmful will become more scarce. This principle is general, and applies to any system of individuals which reproduce; it is most commonly applied to systems of living organisms.

==General Requirements==
Natural selection will automatically take place in any system which follows a certain set of rules. These rules are:

1) There must be a set of individuals.

2) These individuals must reproduce somehow.

3) The probability or rate of reproduction must be somehow dependent on a heritable trait of the individual (where a heritable trait is one that is more likely to be present in an individual's offspring than it is in the general population).

In any such system, individuals whose traits allow them to reproduce more effectively will soon come to dominate the population.

Natural selection has been called a tautology because it follows from its definition, and because it has no observable consequences by itself that anyone has ever tested against an alternate theory.

== Variation and Randomness ==
Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. In this case, some of the offspring of an individual will be better (where "better" is defined as "more likely to successfully reproduce"--one can think of it as scoring higher on an evaluation) and some will be worse. The higher-scoring offspring will soon come to dominate the population, and over successive generations the average score will also rise.

==Role in Life Sciences==
Natural selection is a principle that was popularized by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms. They used the term "natural" to mean that it occurred in nature, as opposed to selection performed by animal breeders or by a deity. They also used the slogan "survival of the fittest" as another way of explaining natural selection.

Together with [[mutation]] (an altogether distinct phenomenon that should not be confused with natural selection), natural selection forms the basis of evolutionary theory. As stated above, in any system where selection combines with random variation, successive generations will become better adapted to reproduce. [[Evolution]] is the theory that this combination of genetic variation (which may be either mutation of the parent or, in most cases, sexual reproduction) and natural selection leads to [[speciation]].

Natural selection has been used to explain many organism traits. For example, deer run fast because slower deer have been eaten by predators, and the faster deer are more likely to pass their traits to the next generation. [[Selection pressure]] is seldom so one-sided; for example, the long tail of the [[peacock]] leaves it vulnerable to predators. However, since peahens are far less likely to mate with short-tailed peacocks, a long tail is an overall advantage and thus is selected for.

== An Example ==
Here is an example of how an engineer might use an algorithm that is analogous to the combination of mutation and natural selection in the evolution of organisms.

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself. Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over. Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence. Note also that the final dam may be very different from any of the original dams.

== Local and Non-Local Improvement ==
The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation. Again returning to the peacock, it might be an overall advantage to have a very short tail or no tail at all, since predators would be easy to avoid. However, since a ''slightly'' shorter tail gives little help in avoiding predators and also is much less attractive to females, short tails are unlikely to come about.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Talk:Natural selection

2007-07-05T16:12:21Z

Elevens:

== Changes to article ==

Apologies, forgot to add the reason for change!

Adding more detail about the mechanisms of natural selection and known examples.

==Industrial melanism dispute==

Cut entire contents of section:
*In England during the [[industrial revolution]] pollution killed mosses and lichens on tree trunks, turning them from light colours to dark brown. Before this occurred most specimens of the peppered moth ''Biston betularia'' had white wings with black spots - giving a peppered appearance. During the period with dark tree trunks (1849 to circa 1970) the white version of ''betularia'' was easily predated on by birds, decreasing the frequency of the white-wing allele. Individuals with dark wings caused by high concentrations of melanin became much more frequent and the allele frequency for melanic moths increased. When pollution levels were reduced in the late 1960s the trees gained more moss and lichens, making the trunks lighter and predation selected against melanic forms of the peppered moth. It is now thought that the proportions of white to melanic moths in England have now returned to pree-1849 levels.

[[Jonathan Wells]] points out the mistakes in this. For one thing, photos of moths resting on tree trunks had to be staged, because photographers couldn't find any moths doing this: they actually rest on the undersides of leaves. --[[User:Ed Poor|Ed Poor]] 20:50, 23 March 2007 (EDT)
"
Even advocates of using the peppered moth story to support natural selection admit that it isn't supported by the science:

*there are differences between the explanations given in popularizations and introductory textbooks, which are intended for children and the lay public, and what is actually known about the phenomenon as it is discussed in journal articles intended for scientists. [http://www.pandasthumb.org/archives/2005/05/welcome_article.html (Panda's Thumb)]

Wells wrote:
*Kettlewell's experiments supposedly demonstrated that cryptic coloration and selective bird predation are the principle causes of industrial melanism were discredited by (a) findings in the 1960's and 1970's that other factors (such as migration and non-visual selection) had to be invoked to account for observed geographical distributions, (b) reports that the rise and fall of melanism were not correlated with lichen cover on tree trunks in the U.S. or many parts of the U.K., (c) research in the 1980's showing that peppered moths in the wild do not normally rest on tree trunks (where Kettlewell conducted his experiments), and (d) revelations that all photographs of peppered moths on tree trunks have been staged, either by manually positioning live moths or by pinning or gluing dead ones. [http://www.nmsr.org/jonwells.htm]

Now, how do we write about all this in the article? --[[User:Ed Poor|Ed Poor]] 21:00, 23 March 2007 (EDT)

== Spelling Changes ==

I fail to see why it was necessary to go through and change all the spellings from one form of English to another, English can be understood as long as the spellings are correct, which they were. Please could someone explain to me the significance of this? --[[User:Tomt|Tomt]] 11:57, 25 March 2007 (EDT)

:I changed "colours" to "colors", as only the latter is considered correct in American English. American English is the most popular language in the world. British spellings give the article an archaic flavor. [[User:RSchlafly|RSchlafly]] 13:33, 25 March 2007 (EDT)

::I would be interested to see some statistics to back up the claim that American English is the most popular language in the world.[[User:MatteeNeutra|MatteeNeutra]] 13:41, 25 March 2007 (EDT)

::: I just did some simple web searches with Google and Yahoo, and I found 3 to 4 times as many pages with the American spellings. [[User:RSchlafly|RSchlafly]] 14:13, 25 March 2007 (EDT)

::::So you did a search using '''American''' search engines for random words and you are now citing that as evidence that American English is the most popular language in the world?[[User:MatteeNeutra|MatteeNeutra]] 17:32, 25 March 2007 (EDT)

::I am, quite frankly, a little insulted that you find my language archaic. It is correct English, whether or not it is American or British and does not impede understanding. Also, please provide some actual evidence for the prevalence of American English, as I have been unable to find any in 15 minutes of searching the internet. What happens to your statistics iif you searched on the German Google? Would you argue that Conservapedia should be in German? I think not. --[[User:Tomt|TomT]] 14:47, 25 March 2007 (EDT)

::: I am not trying to offend the British or the Germans. I am just trying to use language that will be commonly understood. Maybe there will be versions of Conservapedia in other languages some day, I don't know. In the meantime, American English is preferred. [[User:RSchlafly|RSchlafly]] 17:27, 25 March 2007 (EDT)
::::I apologise if I suggested you insulted the Germans, I was merely using it as an example. There is nowhere that I can find on this website that tells us that American English is preferred. Your opinion is especially contradicted by the point that informs us that "We have decided to remove Conservapedia Commandment 5. (American Spellings must be used)", quoted from the Conservapedia talk page. --[[User:Tomt|TomT]] 17:45, 25 March 2007 (EDT)

::::: Thanks for pointing out that change. Two sentences later, it says, "However we would like Conservapedia to be as consistant as possible so we will continue to include american spellings as a style guideline." Hmmm. I prefer the spelling ''consistent''. [[User:RSchlafly|RSchlafly]] 19:07, 25 March 2007 (EDT)

== Nested Categories? ==

Why has this article on the science biology been removed from the science and biology categories???

:''Category:Genetics'' is itself a member of ''Category:Biology'', which is a member of ''Category:Science''. Listing all three is redundant, and makes the higher categories rather unwieldly. [[User:Tsumetai|Tsumetai]] 09:18, 5 April 2007 (EDT)

:How is listing all three redundant? And what do you mean by unwieldy? Surely each category should contain a list of ''all'' the articles it contains?

==Intro==

Cut from intro:

:This selection process is in response to forces in the natural world, as opposed to [[artificial selection]], whereby selection is made by a human being, such as a farmer selecting his breeding stock or variety of [[plant]].

How is it a "response"? Do the animals sit down for a meeting and then vote on it?

And isn't it the biggest bone of contention, whether this principle '''does''' any selecting, just like an Actual Breeder? --[[User:Ed Poor|Ed Poor]] 10:37, 12 April 2007 (EDT)

Basically it just comes down to this, if you able to survive under the current conditions you will live, if you're not, you'll die.
You don't have to be perfectly suited to your environment, you only have to survive even if it's through luck.

Eventually though, a life form that's better suited to its environment has a greater chance of survival, so does its offspring, and the traits that make them different from the ones who have a smaller chance of survival will become more common within the population: then we would say nature has "selected" those traits and thus the life forms carrying them.

The genetic mutations that cause traits to change are random and sometimes don't happen fast enough to ensure the survival of at least some members of the population when the environment changes, but on the long run the system works.
In fact natural selection shapes everything, from birds to planets to entire galaxies.

[[User:Middle Man|Middle Man]]

:Just to add for Ed's sake, sexual selection is a major principle behind this.--[[User:Tims|TimS]] 10:29, 23 April 2007 (EDT)

Ed, a phenotype is the displayed traits of a genome. The difference between a genotype and phenotype is that genotypes are everything your genome codes for while your phenotype is everything that is expressed.--[[User:Tims|TimS]] 22:25, 8 May 2007 (EDT)

:If we're playing buzzword bingo, you just won - and I lost. :-(

:What's a [[genome]], [[genotype]], [[phenotype]] ... and what does it mean to "express" any of this? In plain English without all the mumbo-jumbo (as Jack said to the angel in "[[Family Man]]"). --[[User:Ed Poor|Ed Poor]] 22:30, 8 May 2007 (EDT)

:: Phenotype examples: Brown hair, blue eyes, wrinkly skin on a pea, type B blood. Something that is observable.
:: Genotype examples: Brown hair gene, blond hair gene. Two blue eye genes. two wrinkly skin on pea genes. The genes for type B blood and type O blood.
:: That help somewhat? --[[User:Mtur|Mtur]] 22:32, 8 May 2007 (EDT)

== Rewrite ==

Hi Ed, could you just clarify what work you need doing to this article so that I can improve it please? I'll be happy to oblige if you provide a list of the things that need changing. --[[User:Tomt|TomT]] 14:37, 2 June 2007 (EDT)

I believe I've clarified the role of natural selection in evolution. Let me know if you have any comments.--[[User:Elevens|Elevens]] 12:12, 5 July 2007 (EDT)

Talk:Natural selection

2007-07-05T16:11:34Z

Elevens:

Natural selection

2007-07-05T16:09:19Z

Elevens: /* General Requirements */

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
The fundamental statement of '''natural selection''' is that heritable traits which are beneficial will become more numerous in successive generations, while heritable traits which are harmful will become more scarce. This principle is general, and applies to any system of individuals which reproduce; it is most commonly applied to systems of living organisms.

==General Requirements==

Natural selection will automatically take place in any system which follows a certain set of rules. These rules are:

1) There must be a set of individuals.

2) These individuals must reproduce somehow.

3) The probability or rate of reproduction must be somehow dependent on a heritable trait of the individual (where a heritable trait is one that is more likely to be present in an individual's offspring than it is in the general population).

In any such system, individuals whose traits allow them to reproduce more effectively will soon come to dominate the population.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. In this case, some of the offspring of an individual will be better (where "better" is defined as "more likely to successfully reproduce"--one can think of it as scoring higher on an evaluation) and some will be worse. The higher-scoring offspring will soon come to dominate the population, and over successive generations the average score will also rise.

==Role in Life Sciences==

Natural selection is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms. Together with [[mutation]] (an altogether distinct phenomenon that should not be confused with natural selection), natural selection forms the basis of evolutionary theory. As stated above, in any system where selection combines with random variation, successive generations will become better adapted to reproduce. [[Evolution]] is the theory that this combination of genetic variation (which may be either mutation of the parent or, in most cases, sexual reproduction) and natural selection leads to [[speciation]].

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself. Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over. Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence. Note also that the final dam may be very different from any of the original dams.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Natural selection

2007-07-05T16:08:59Z

Elevens: /* General Requirements */

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
The fundamental statement of '''natural selection''' is that heritable traits which are beneficial will become more numerous in successive generations, while heritable traits which are harmful will become more scarce. This principle is general, and applies to any system of individuals which reproduce; it is most commonly applied to systems of living organisms.

==General Requirements==

Natural selection will automatically take place in any system which follows a certain set of rules. These rules are:
1) There must be a set of individuals.
2) These individuals must reproduce somehow.
3) The probability or rate of reproduction must be somehow dependent on a heritable trait of the individual (where a heritable trait is one that is more likely to be present in an individual's offspring than it is in the general population).

In any such system, individuals whose traits allow them to reproduce more effectively will soon come to dominate the population.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. In this case, some of the offspring of an individual will be better (where "better" is defined as "more likely to successfully reproduce"--one can think of it as scoring higher on an evaluation) and some will be worse. The higher-scoring offspring will soon come to dominate the population, and over successive generations the average score will also rise.

==Role in Life Sciences==

Natural selection is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms. Together with [[mutation]] (an altogether distinct phenomenon that should not be confused with natural selection), natural selection forms the basis of evolutionary theory. As stated above, in any system where selection combines with random variation, successive generations will become better adapted to reproduce. [[Evolution]] is the theory that this combination of genetic variation (which may be either mutation of the parent or, in most cases, sexual reproduction) and natural selection leads to [[speciation]].

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself. Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over. Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence. Note also that the final dam may be very different from any of the original dams.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Sexual reproduction

2007-07-05T16:06:35Z

Elevens: Noted that sexual reproduction leads to genetic variation

{{merge|procreation}}
'''Sexual reproduction''' is reproduction by [[meiosis]] and fusion of the [[gametes]] from a single parent [[organism]] (selfing) or two parent organisms. The parent organisms are usually a [[male]] and a [[female]].<ref>Freeman, Scott, ''Biological Science''. Prentice Hall 2005.</ref> In sexual reproduction the gametes produced by the male and female each contain half of the parent's two sets of [[gene]]s, and fusion of the gametes creates a new [[cell]] which has two sets of genes, one set from each parent. This combination of genes leads to much genetic variation between parents and offspring. Many [[species]] reproduce sexually, such as [[human]]s, while some species (including many plants and some animals) can reproduce either sexually or [[asexual reproduction|asexually]].

==References==
<references/>

[[Category:Biology]]

Natural selection

2007-07-05T16:04:35Z

Elevens: Clarified role in evolution; rearranged the order of sections

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
The fundamental statement of '''natural selection''' is that heritable traits which are beneficial will become more numerous in successive generations, while heritable traits which are harmful will become more scarce. This principle is general, and applies to any system of individuals which reproduce; it is most commonly applied to systems of living organisms.

==General Requirements==

Natural selection will automatically take place in any system which follows a certain set of rules. These rules are:
1) There must be a set of individuals.
2) These individuals must reproduce somehow.
3) The probability or rate of reproduction must be somehow dependent on a trait of the individual which its offspring also have (or at least have with greater probability than the general population).

In any such system, individuals whose traits allow them to reproduce more effectively will soon come to dominate the population.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. In this case, some of the offspring of an individual will be better (where "better" is defined as "more likely to successfully reproduce"--one can think of it as scoring higher on an evaluation) and some will be worse. The higher-scoring offspring will soon come to dominate the population, and over successive generations the average score will also rise.

==Role in Life Sciences==

Natural selection is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms. Together with [[mutation]] (an altogether distinct phenomenon that should not be confused with natural selection), natural selection forms the basis of evolutionary theory. As stated above, in any system where selection combines with random variation, successive generations will become better adapted to reproduce. [[Evolution]] is the theory that this combination of genetic variation (which may be either mutation of the parent or, in most cases, sexual reproduction) and natural selection leads to [[speciation]].

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself. Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over. Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence. Note also that the final dam may be very different from any of the original dams.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Natural selection

2007-07-05T15:50:13Z

Elevens: Added a brief, concise definition at the beginning; simplified the explanation of natural selection's generality.

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
The fundamental statement of '''natural selection''' is that heritable traits which are beneficial will become more numerous in successive generations, while heritable traits which are harmful will become more scarce. This principle is general, and applies to any system of individuals which reproduce; it is most commonly applied to systems of living organisms.

==Role in Life Sciences==

Natural selection is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms.

These organisms have to be able to survive long enough to reproduce, and produce viable offspring capable of the same, in order to ensure the continuing survival of their genetic traits. They do not have to be perfectly adapted to their environment; they only have to be able to survive in it.

Furthermore, an organism may be well adapted to one environment but not be able to survive in another.

Natural selection is not [[mutation]]. It does not make anything new, alter anything, etc. Natural selection can cause extinction based on survival of the fittest, but the processes of creation and mutation lie outside the scope of natural selection.

==General Requirements==

Natural selection will automatically take place in any system which follows a certain set of rules. These rules are:
1) There must be a set of individuals.
2) These individuals must reproduce somehow.
3) The probability or rate of reproduction must be somehow dependent on a trait of the individual which its offspring also have (or at least have with greater probability than the general population).

In any such system, individuals whose traits allow them to reproduce more effectively will soon come to dominate the population.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. Some of the new, slightly different copies of an individual will be evaluated differently from the original, scoring either higher or lower depending on what changed. If this process is iterated many times, individuals which score well on the evaluations will become more and more numerous, and the highest score of an individual will tend to rise. It has been suggested<ref>[Richard Dawkins, ''Climbing Mount Improbable'']</ref> that this process can lead to the appearance of design, as the individuals that are present after many iterations of this process will usually score very well on the evaluation (since those that do not score well are eliminated).

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself. Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over. Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Scientific theory

2007-07-02T20:00:32Z

Elevens:

A '''scientific theory''' is more substantial than a conjecture or [[hypothesis]], but may not be verified as consistent with empirical data. <ref>For example, scientists may refer to phlogiston theory or ether theory, even though empirical verification was lacking.</ref>

It is a plausible and consistent explanation for observable phenomena.

To be considered [[science|scientific]], a theory must be [[falsifiable]].
This means that there must be some way to do experiments that could counter the theory's predictions, thus disproving the current theory.
<ref>"A theory not only explains known facts; it also allows scientists to make predictions of what they should observe if a theory is true. Scientific theories are testable. New evidence should be compatible with a theory. If it isn't, the theory is refined or rejected." [http://www.amnh.org/exhibitions/darwin/evolution/theory.php] </ref>

Generally accepted scientific theories have been tested and survived over time, have evolved when appropriate, and modified toward consistency with newly discovered data, have not been shown to be false and can make predictions about natural phenomena. <ref>http://www.thefreedictionary.com/theory </ref> Scientific theories can sometimes be used as the basis for industrial and technical developments.

A scientific theory does not necessarily have to have strong experimental support or accepted by the scientific community. Scientists often refer to untested theories and competing theories. Theories can be extremely well-confirmed, such as conservation of energy, or speculative, such as [[String Theory]].

No scientific theory can be said to be absolutely true, but a successful theory is most consistent with the actual behavior of the universe. When a phenomenon is discovered that is inconsistent with the prevailing theory, the theory is either revised or thrown out entirely. An example of this is [[Newtonian mechanics]]--while Newton's 3 laws of motion provide extremely accurate descriptions/predictions of the behavior of medium-sized objects at low speeds, they are inconsistent with the behavior of very large, very fast, or very small objects. Newtonian mechanics has been shown to be a limiting case of the [[theory of relativity]] (in the limit where velocity goes to 0) and [[quantum mechanics]] (in the limit where [[Planck's constant]] goes to 0, essentially the limit of large objects). Usually a theory which is inconsistent with some experimental evidence is not completely falsified; it is instead shown to be a simplified version of a more complete theory.

== Common usage ==
Evolutionists frequently argue that the word "theory" means very different things to scientists and non-scientists. For example, a PBS TV show says: <ref>http://www.pbs.org/wgbh/evolution/library/11/2/e_s_1.html</ref>
:''When we use the word "theory" in everyday life, we usually mean an idea or a guess, but the word has a much different meaning in science. This video examines the vocabulary essential for understanding the nature of science and evolution and illustrates how evolution is a powerful, well-supported scientific explanation for the relatedness of all life.''

The American Museum of Natural History exhibit on Darwin says: <ref>http://www.amnh.org/exhibitions/darwin/evolution/theory.php</ref>
:''In everyday use, the word "theory" often means an untested hunch, or a guess without supporting evidence. But for scientists, a theory has nearly the opposite meaning. A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts.''

In science a theory is something that ties together facts. For example, an apple falling to the ground when you let go of it is a fact. From this we can hypothesize that there is some force pulling it down. The set of observations and mathematical formulae that explain how this force works, and the experiments which demonstrate that those observations and formulae are correct is called the Theory of Gravity.

==Notes and references==
<references/>

[[Category:Science]]

Scientific theory

2007-07-02T19:59:28Z

Elevens:

A '''scientific theory''' is more substantial than a conjecture or [[hypothesis]], but may not be verified as consistent with empirical data. <ref>For example, scientists may refer to phlogiston theory or ether theory, even though empirical verification was lacking.</ref>

It is a plausible and consistent explanation for observable phenomena.

To be considered [[science|scientific]], a theory must be [[falsifiable]].
This means that there must be some way to do experiments that could counter the theory's predictions, thus disproving the current theory.
<ref>"A theory not only explains known facts; it also allows scientists to make predictions of what they should observe if a theory is true. Scientific theories are testable. New evidence should be compatible with a theory. If it isn't, the theory is refined or rejected." [http://www.amnh.org/exhibitions/darwin/evolution/theory.php] </ref>

Generally accepted scientific theories have been tested and survived over time, have evolved when appropriate, and modified toward consistency with newly discovered data, have not been shown to be false and can make predictions about natural phenomena. <ref>http://www.thefreedictionary.com/theory </ref> Scientific theories can sometimes be used as the basis for industrial and technical developments.

A scientific theory does not necessarily have to have strong experimental support or accepted by the scientific community. Scientists often refer to untested theories and competing theories. Theories can be extremely well-confirmed, such as conservation of energy, or speculative, such as [[String Theory]].

No scientific theory can be said to be absolutely true, but a successful theory is most consistent with the actual behavior of the universe. When a phenomenon is discovered that is inconsistent with the prevailing theory, the theory is either revised or thrown out entirely. An example of this is [[Newtonian mechanics]]--while Newton's 3 laws of motion provide extremely accurate descriptions/predictions of the behavior of medium-sized objects at low speeds, they are inconsistent with the behavior of very large, very fast, or very small objects. Newtonian mechanics has been shown to be a limiting case of [[general relativity]] (in the limit where velocity goes to 0) and [[quantum mechanics]] (in the limit where [[Planck's constant]] goes to 0, essentially the limit of large objects). Usually a theory which is inconsistent with some experimental evidence is not completely falsified; it is instead shown to be a simplified version of a more complete theory.

== Common usage ==
Evolutionists frequently argue that the word "theory" means very different things to scientists and non-scientists. For example, a PBS TV show says: <ref>http://www.pbs.org/wgbh/evolution/library/11/2/e_s_1.html</ref>
:''When we use the word "theory" in everyday life, we usually mean an idea or a guess, but the word has a much different meaning in science. This video examines the vocabulary essential for understanding the nature of science and evolution and illustrates how evolution is a powerful, well-supported scientific explanation for the relatedness of all life.''

The American Museum of Natural History exhibit on Darwin says: <ref>http://www.amnh.org/exhibitions/darwin/evolution/theory.php</ref>
:''In everyday use, the word "theory" often means an untested hunch, or a guess without supporting evidence. But for scientists, a theory has nearly the opposite meaning. A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts.''

In science a theory is something that ties together facts. For example, an apple falling to the ground when you let go of it is a fact. From this we can hypothesize that there is some force pulling it down. The set of observations and mathematical formulae that explain how this force works, and the experiments which demonstrate that those observations and formulae are correct is called the Theory of Gravity.

==Notes and references==
<references/>

[[Category:Science]]

Scientific theory

2007-07-02T19:57:49Z

Elevens:

A '''scientific theory''' is more substantial than a conjecture or [[hypothesis]], but may not be verified as consistent with empirical data. <ref>For example, scientists may refer to phlogiston theory or ether theory, even though empirical verification was lacking.</ref>

It is a plausible and consistent explanation for observable phenomena.

To be considered [[science|scientific]], a theory must be [[falsifiable]].
This means that there must be some way to do experiments that could counter the theory's predictions, thus disproving the current theory.
<ref>"A theory not only explains known facts; it also allows scientists to make predictions of what they should observe if a theory is true. Scientific theories are testable. New evidence should be compatible with a theory. If it isn't, the theory is refined or rejected." [http://www.amnh.org/exhibitions/darwin/evolution/theory.php] </ref>

Generally accepted scientific theories have been tested and survived over time, have evolved when appropriate, and modified toward consistency with newly discovered data, have not been shown to be false and can make predictions about natural phenomena. <ref>http://www.thefreedictionary.com/theory </ref> Scientific theories can sometimes be used as the basis for industrial and technical developments.

A scientific theory does not necessarily have to have strong experimental support or accepted by the scientific community. Scientists often refer to untested theories and competing theories. Theories can be extremely well-confirmed, such as conservation of energy, or speculative, such as [[String Theory]].

No scientific theory can be said to be absolutely true, but a successful theory is most consistent with the actual behavior of the universe. When a phenomenon is discovered that is inconsistent with the prevailing theory, the theory is either revised or thrown out entirely. An example of this is Newtonian mechanics--while Newtons 3 laws of motion provide extremely accurate descriptions/predictions of the behavior of medium-sized objects at low speeds, they are inconsistent with the behavior of very large, very fast, or very small objects. Newtonian mechanics has been shown to be a limiting case of general relativity (in the limit where velocity goes to 0) and quantum mechanics (in the limit where Planck's constant goes to 0, essentially the limit of large objects). Usually a theory which is inconsistent with some experimental evidence is not completely falsified; it is instead shown to be a simplified version of a more complete theory.

== Common usage ==
Evolutionists frequently argue that the word "theory" means very different things to scientists and non-scientists. For example, a PBS TV show says: <ref>http://www.pbs.org/wgbh/evolution/library/11/2/e_s_1.html</ref>
:''When we use the word "theory" in everyday life, we usually mean an idea or a guess, but the word has a much different meaning in science. This video examines the vocabulary essential for understanding the nature of science and evolution and illustrates how evolution is a powerful, well-supported scientific explanation for the relatedness of all life.''

The American Museum of Natural History exhibit on Darwin says: <ref>http://www.amnh.org/exhibitions/darwin/evolution/theory.php</ref>
:''In everyday use, the word "theory" often means an untested hunch, or a guess without supporting evidence. But for scientists, a theory has nearly the opposite meaning. A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts.''

In science a theory is something that ties together facts. For example, an apple falling to the ground when you let go of it is a fact. From this we can hypothesize that there is some force pulling it down. The set of observations and mathematical formulae that explain how this force works, and the experiments which demonstrate that those observations and formulae are correct is called the Theory of Gravity.

==Notes and references==
<references/>

[[Category:Science]]

Natural selection

2007-07-02T17:10:06Z

Elevens: Clarified that the "engineer" in my example does not have to be intelligent.

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
'''Natural selection''' is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms.

These organisms have to be able to survive long enough to reproduce, and produce viable offspring capable of the same, in order to ensure the continuing survival of their genetic traits. They do not have to be perfectly adapted to their environment; they only have to be able to survive in it.

Furthermore, an organism may be well adapted to one environment but not be able to survive in another.

Natural selection is not [[mutation]]. It does not make anything new, alter anything, etc. Natural selection can cause extinction based on survival of the fittest, but the processes of creation and mutation lie outside the scope of natural selection.

==Generality==

While it is commonly applied to competition between living organisms, natural selection is far more general mathematical model. In general, natural selection applies to any system where a group of different "individuals" (where an "individual" could be anything from a bacterium to a computer program to an architectural design) is evaluated by some metric; each individual is then either discarded or duplicated based on the results of the evaluation (usually with some stochastic weighting of the probabilities of discarding/duplication). The process is then repeated. In most examples, the metric of evaluation is relative--that is, an individual only scores "well" if its score is high compared to the rest of the group.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. Some of the new, slightly different copies of an individual will be evaluated differently from the original, scoring either higher or lower depending on what changed. If this process is iterated many times, individuals which score well on the evaluations will become more and more numerous, and the highest score of an individual will tend to rise. It has been suggested<ref>[Richard Dawkins, ''Climbing Mount Improbable'']</ref> that this process can lead to the appearance of design, as the individuals that are present after many iterations of this process will usually score very well on the evaluation (since those that do not score well are eliminated).

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself. Note that this engineer need not be conscious of the overall goal--he is just applying a simple algorithm over and over. Indeed, the engineer need not be conscious of anything at all--his task could be performed automatically and without sentience or intelligence.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Natural selection

2007-07-02T16:48:33Z

Elevens: Added a reference

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
'''Natural selection''' is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms.

These organisms have to be able to survive long enough to reproduce, and produce viable offspring capable of the same, in order to ensure the continuing survival of their genetic traits. They do not have to be perfectly adapted to their environment; they only have to be able to survive in it.

Furthermore, an organism may be well adapted to one environment but not be able to survive in another.

Natural selection is not [[mutation]]. It does not make anything new, alter anything, etc. Natural selection can cause extinction based on survival of the fittest, but the processes of creation and mutation lie outside the scope of natural selection.

==Generality==

While it is commonly applied to competition between living organisms, natural selection is far more general mathematical model. In general, natural selection applies to any system where a group of different "individuals" (where an "individual" could be anything from a bacterium to a computer program to an architectural design) is evaluated by some metric; each individual is then either discarded or duplicated based on the results of the evaluation (usually with some stochastic weighting of the probabilities of discarding/duplication). The process is then repeated. In most examples, the metric of evaluation is relative--that is, an individual only scores "well" if its score is high compared to the rest of the group.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. Some of the new, slightly different copies of an individual will be evaluated differently from the original, scoring either higher or lower depending on what changed. If this process is iterated many times, individuals which score well on the evaluations will become more and more numerous, and the highest score of an individual will tend to rise. It has been suggested<ref>[Richard Dawkins, ''Climbing Mount Improbable'']</ref> that this process can lead to the appearance of design, as the individuals that are present after many iterations of this process will usually score very well on the evaluation (since those that do not score well are eliminated).

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Natural selection

2007-07-02T16:44:44Z

Elevens: I added sections illustrating the mathematical generality of natural selection, what happens when natural selection and random variation combine, and its effects and limitations.

{{rewrite|Its role in [[Evolution]] is expressed vaguely. How does natural selection "help" bring a new species into existence? Merely by weeding out the "mistakes"?}}
'''Natural selection''' is a principle that was proposed by [[Charles Darwin]] and Alfred Russel Wallace, who noted that organisms which were better adapted to their environment tended to survive longer and reproduce more than less well-adapted organisms.

These organisms have to be able to survive long enough to reproduce, and produce viable offspring capable of the same, in order to ensure the continuing survival of their genetic traits. They do not have to be perfectly adapted to their environment; they only have to be able to survive in it.

Furthermore, an organism may be well adapted to one environment but not be able to survive in another.

Natural selection is not [[mutation]]. It does not make anything new, alter anything, etc. Natural selection can cause extinction based on survival of the fittest, but the processes of creation and mutation lie outside the scope of natural selection.

==Generality==

While it is commonly applied to competition between living organisms, natural selection is far more general mathematical model. In general, natural selection applies to any system where a group of different "individuals" (where an "individual" could be anything from a bacterium to a computer program to an architectural design) is evaluated by some metric; each individual is then either discarded or duplicated based on the results of the evaluation (usually with some stochastic weighting of the probabilities of discarding/duplication). The process is then repeated. In most examples, the metric of evaluation is relative--that is, an individual only scores "well" if its score is high compared to the rest of the group.

== Variation and Randomness ==

Natural selection becomes interesting when there is the possibility of random variation in the duplication of individuals--in other words, when an individual is copied, the copy may be slightly different from the original. It is important to note that, as stated above, the ''mechanism'' for this variation is not explained or even taken into account by natural selection. All that matters is that there is ''some'' process that produces variation. Some of the new, slightly different copies of an individual will be evaluated differently from the original, scoring either higher or lower depending on what changed. If this process is iterated many times, individuals which score well on the evaluations will become more and more numerous, and the highest score of an individual will tend to rise. It has been suggested that this process can lead to the appearance of design, as the individuals that are present after many iterations of this process will usually score very well on the evaluation (since those that do not score well are eliminated).

== An Example ==

An engineer starts with 10,000 different sets of plans for a hydroelectric dam. His dam must complete two basic tasks: it must hold back a lake with minimal flooding of the surrounding area, and it must maximize power generation. The intrinsic worth of a dam is determined by how well it completes these tasks; a dam which produces 100 kW of electricity while only raising water levels 2 feet is superior to one which produces 10 kW of electricity while raising water levels 5 feet. In our simplified example, let us assume that the design of a dam is based on just a few numerical parameters: height, width, thickness, concrete mixture, hydroelectric turbine size, curvature, etc. After evaluating all the dams, the engineer picks the 100 best and discards the rest. He then copies each of these dams 100 times. When copying, the engineer randomly introduces minor differences: say he rolls a die each time he copies a design parameter; if he rolls a six, he then changes that parameter by 1%, flipping a coin to determine if he will increase or decrease the parameter. Once he has finished copying, he will have 10,000 more dams, most of them very similar to the original 100 but with some small differences. He then evaluates these 10,000 dams again, picks the best 100, and copies them again, introducing random "errors" in the same way. After completing this process several thousand times, the engineer has 10,000 dams, all of which perform excellently. He picks the best of them and thus has an excellent design, without ever doing any real "design" himself.

== Local and Non-Local Improvement ==

The above section illustrates how natural selection and random variation can combine to create improved individuals. However, it is important to note that there is no long-term planning involved in natural selection. This means that all changes must be locally beneficial in order to survive. Essentially, no improvement can take place if a deterioration must take place first. In order for a change to propagate to future "generations" of individuals, it must not be significantly harmful to ''any'' generation. In the language of the above example, let us say that one of the dams would be much improved if the curvature were increased by 10%, but would be worsened considerably if the curvature was 3 to 7% higher. Since curvature can only change by 1% at a time, and a regime of "bad" curvature lies between the current regime and the regime of "good" curvature, the dam will never reach the "good" regime. Thus, in order for a large change to take place over several generations, it must be beneficial (or at least not significantly harmful) at ''each'' generation.

* [[Theory of evolution through natural selection]]

== References ==
<references/>

[[Category:Biology]]
[[Category:Genetics]]
[[Category:Evolution]]

Rush Limbaugh

2007-06-26T16:35:07Z

Elevens:

'''Rush Limbaugh''' (born January 12, 1951) is a [[conservative]] [[United States of America|American]] radio talk show host.
[[Image:Limbaugh.jpg|thumb|right|Rush Limbaugh]]

== Radio ==

Limbaugh hosts a radio show famed for its blustery denunciations of anything [[liberal]]. He is often at odds with [[liberal]] activist [[Al Franken]]<ref>[http://fireside.designcommunity.com/topic-9993.html Forum thread] discussing a NYT Editorial</ref>. He habitually refers to [[feminists]] who support [[abortion]] as ''feminazis'' and to his own self as "talent on loan from God".

Limbaugh's style has been credited with "reviving AM radio in the United States, and is considered by many to have been a catalyst for the [[Republican Party]]'s 1994 Congressional victories"<ref>[http://select.nytimes.com/gst/abstract.html?res=F10813FA3B5D0C708EDDAB0894DE494D81&n=Top%2fReference%2fTimes%20Topics%2fPeople%2fL%2fLimbaugh%2c%20Rush Radio Talk Show Host Fears For True Conservatism's Fate], New York Times</ref>.
Rush's conservative talk show is nationally syndicated and averages over 13.5 million listeners weekly, making Rush the '#1 Radio Talk Show Host'.<ref>
[http://www.talkers.com/main/index.php?option=com_content&task=view&id=17&Itemid=34 The Top Talk Radio Audiences] Tallkers magazine online</ref>

On October 6, 2003 Limbaugh told his audience he was addicted to OxyContin and other painkillers. <ref>The Rush Limbaugh Show, October 6, 2007.</ref> Limbaugh underwent treatment for his addiction, and charges against him for alleged "doctor shopping" to procure prescription medications were dropped on the condition that he continue treatment for his addiction.<ref>http://www.cbsnews.com/stories/2006/04/28/national/main1561324.shtml</ref>

== Other Media Work ==

The Limbaugh Letter is a monthly publication that contains conservative articles and humor in Rush's style.

Limbaugh is involved in the conservative satire show "The 1/2 Hour News Hour" show on the [[Fox News Channel]]. <ref>
[http://www.washingtonpost.com/wp-dyn/content/article/2007/02/16/AR2007021602098.html Fox News Channel's '1/2 Hour News Hour': Right Funny, in Spots] washingtonpost.com</ref>

Limbaugh briefly held a position as a commentator on ESPN's Sunday NFL Countdown pre-game show. He resigned from the show on October 2, 2006 after criticism of his statement that Philadelphia Eagles quaterback Donovan McNabb was overrated because the media wanted to see a black NFL player succeed.<ref>http://espn.go.com/gen/news/2003/1001/1628537.html</ref>

== Alleged Nobel Nomination ==

In 2007, Mark R. Levin of the Landmark Legal Foundation issued a press release giving the text of a letter from the Foundation to the Chairman of the Nobel Institute. The letter "submits the name of Rush Limbaugh as an unsolicited nomination for the 2007 Nobel Peace Prize" for his "tireless efforts to promote liberty, equality and opportunity for all mankind, regardless of race, creed, economic stratum or national origin."<ref>[http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=104&STORY=/www/story/02-01-2007/0004518421&EDATE Landmark Legal Foundation Nominates Rush Limbaugh for 2007 Nobel Peace Prize"</ref>. Nomination for the Nobel Peace Prize is by invitation only, and the names of the nominees and their nominations are kept secret for fifty years.<ref>[http://nobelprize.org/nomination/peace/ Nomination for the Nobel Peace Prize], Nobel Foundation. The position of the Nobel Foundation, with regard to all [http://nobelprize.org/nomination/nomination_facts.html rumored nominations], is "Well, either it's just a rumour, or someone among the invited nominators has leaked information. Since the nominations are kept secret for 50 years, you'll have to wait until then to find out."</ref>

== Drug Abuse Scandal ==

In October of 2003, Limbaugh admitted on his radio show that he had been addicted to prescription painkillers (Oxycodone or hydrocodone).<ref>[http://www.cnn.com/2003/SHOWBIZ/10/10/rush.limbaugh/ "Limbaugh admits addiction to pain medication"</ref> He cited a failed back surgery as the cause of his pain and subsequent dependence on medication. Limbaugh did not comment further on his current state, saying that he would not go into any more detail because of the ongoing police investigation.

==References==
<references/>

==External Links==
*[http://www.rushlimbaugh.com/home/today.guest.html Official Rush Limbaugh website]
{{DEFAULTSORT: Limbaugh, Rush}}
[[Category:Broadcasters]]