Introduction to evolution: Difference between revisions

Revision as of 17:03, 27 January 2008

Revision as of 17:12, 27 January 2008

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[[Image:DNA Overview.png|thumb|right|A section of [[DNA]]]]

Every living organism contains molecules of DNA, which carries genetic information. [[Genes]] are the pieces of DNA that carry this information and they influence the properties of an organism. Genes determine a person's general appearance and to some extent their behavior. If two organisms are closely related, their DNA will be very similar.<ref name= NAS>{{cite web |url=http://www.nap.edu/readingroom/books/evolution98/evol3.html |title= Teaching about evolution and the nature of science |accessdate=2007-12-30 |last= Kennedy |first=Donald |coauthors=(Working group on teaching evolution) |date=1998 |work=Evolution and the nature of science|publisher= The National Academy of Science }}</ref> On the other hand, the more distantly-related two organisms are, the more differences they will have. For example, two brothers will be very closely related and will have very similar DNA, while distant cousins will have far more differences between their DNA. AsSimilarites wellin asDNA showingare howused closely-relatedto twodetermine individualsthe are,relationship DNAbetween canspecies showin howmuch closely-relatedthe twosame speciesmanner areas it is used to show relationships between individuals. For example, comparing [[chimpanzee]]s with [[gorilla]]s and humans shows that there is as much as a 96&nbsp;percent similarity between the DNA of humans and chimps, and that humans and chimpanzees are more closely related to each other than either species are to gorillas.<ref>{{cite web |url= http://news.nationalgeographic.com/news/2005/08/0831_050831_chimp_genes.html |title=Chimps, Humans 96 Percent the Same, Gene Study Finds |accessdate=2007-12-23 |last= Lovgren |first= Stefan |coauthors= |date=2005-08-31 |work= National Geographic News |publisher= National Geographic }}</ref><ref>{{Harv |Carroll|Grenier|Weatherbee|2000| p=}}</ref>

The field of [[molecular systematics]] focuses on measuring the similarities in these molecules and using this information to work out how different types of organisms are related through evolution. These comparisons have allowed biologists to build a ''relationship tree'' of the evolution of life on earth.<ref>{{cite journal |author=Ciccarelli FD, Doerks T, von Mering C, Creevey CJ, Snel B, Bork P |title=Toward automatic reconstruction of a highly resolved tree of life |journal=Science |volume=311 |issue=5765 |pages=1283&ndash;7 |year=2006 |pmid=16513982|accessdate=2008-01-24}}</ref> They have even allowed scientists to unravel the relationships of organisms whose common ancestors lived such a long time ago that no real similarities remain in the appearance of the organisms.