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Macroevolution

2008-07-05T16:07:43Z

ProX: Revert; previous version was opinion based/factually incorrect; added sources

'''Macroevolution''' is a term used by [[Creationists]] to distinguish between what they perceive as different processes within the [[Theory of Evolution]]. However, scientists do not make this distinction, noting that the only difference between micro and macro evolution is the amount of time involved.

Macroevolution refers to the theory that [[natural selection]] can, given enough time, lead to the creation of new [[clade]]s, which are groups of organisms consisting of a single common ancestor and all the descendants of that ancestor. While details of macroevolution are continuously studied by the scientific community, the overall theory behind macroevolution (i.e. [[common descent]]) has been overwhelmingly consistent with empirical data. Predictions of empirical data from the theory of common descent have been so consistent that biologists often refer to it as the on as the "''fact'' of evolution".

Creationists accept that evolutionary change is possible within species ("microevolution"), but deny that one species can evolve into another ("macroevolution"). These arguments are rejected by mainstream science, which holds that there is ample evidence that macroevolution has occurred in the past.

==Methods of Macroevolution==

:[[natural selection]] - is the mechanism by which allele frequency within a population changes over time due to genetic variation and selection pressures.<ref>http://evolution.berkeley.edu/evosite/evo101/IIIENaturalSelection.shtml</ref>
:[[genetic drift]] - is the statistical effect that results from the influence that chance has on the survival of alleles.<ref>http://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtml</ref>
:[[sexual selection]] - is the hypothesis proposed by Charles Darwin that states that the frequency of traits can increase or decrease depending on the attractiveness of the bearer.<ref>http://evolution.berkeley.edu/evosite/evo101/IIIE3Sexualselection.shtml</ref>
:[[neutral evolution]] - is the vast majority of molecular differences are selectively "neutral." The molecular changes represented by these differences do not influence the fitness of the individual organism. As a result, these genomic features are neither subject to, nor explicable by, natural selection.<ref>http://evolution.berkeley.edu/evosite/evo101/IIIE5bNeutraltheory.shtml</ref>
:[[allopatric speciation]] - is when a population splits into two geographically isolated allopatric populations then undergo genotypic and/or phenotypic divergence as they become subjected to dissimilar selective pressures or they independently undergo genetic drift.<ref>http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html</ref><ref>http://evolution.berkeley.edu/evosite/evo101/VC1bAllopatric.shtml</ref>
:[[peripatric speciation]] - is when new species are formed in isolated, small peripheral populations which are prevented from exchanging genes with the main population.<ref>http://evolution.berkeley.edu/evosite/evo101/VC1cPeripatric.shtml</ref>
:[[parapatric speciation]] - is when the zones of two diverging populations are separate but do overlap.<ref>http://evolution.berkeley.edu/evosite/evo101/VC1dParapatric.shtml</ref>
:[[sympatric speciation]]- is when species diverge while inhabiting the same place.<ref>http://evolution.berkeley.edu/evosite/evo101/VC1eSympatric.shtml</ref>

==See also==
*[[Microevolution]]
*[[Theory of evolution]]

==References==
<references/>

[[Category:Evolution]]
[[Category:Science]]
[[Category:Biology]]

Macroevolution

2008-07-05T14:37:15Z

ProX:

The Selfish Gene

2008-07-05T13:36:22Z

ProX:

'''''The Selfish Gene''''' is a book on [[evolution]] by [[Richard Dawkins]], published in 1976. It builds upon the principal theory of George C. Williams's first book ''Adaptation and Natural Selection''. Dawkins coined the term ''selfish gene'' as a way of expressing the gene-centered view of evolution, which holds that evolution is best viewed as acting on [[gene]]s, and that selection at the level of organisms or populations almost never overrides selection based on genes. An organism is expected to evolve to maximize its [[inclusive fitness]] – the number of copies of its genes passed on globally (rather than by a particular individual). As a result, populations will tend towards an [[evolutionarily stable strategy]]. The book also coins the term ''[[meme]]'' for a unit of human cultural evolution analogous to the gene, suggesting that such "selfish" replication may also model human culture, in a different sense. Memetics has become the subject of many studies since the publication of the book.

=="Selfish" genes==
In describing genes as being "selfish", the author does not intend (as he states unequivocally in the work) to imply that they are driven by any motives or will – merely that their effects can be accurately described ''as if'' they do. The contention is that the genes that get passed on are the ones whose consequences serve their own implicit interests (to continue being replicated), not necessarily those of the organism, much less any larger level. This view explains altruism at the individual level in nature, especially in kin relationships (when an individual sacrifices its own life to protect the lives of kin, it is acting in the interest of its own genes).