Life Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Multicellular structure === [[Multicellular organism]]s may have first evolved through the formation of [[Colony (biology)|colonies]] of identical cells. These cells can form group organisms through [[cell adhesion]]. The individual members of a colony are capable of surviving on their own, whereas the members of a true multi-cellular organism have developed specialisations, making them dependent on the remainder of the organism for survival. Such organisms are formed [[Clone (cell biology)|clonally]] or from a single [[germ cell]] that is capable of forming the various specialised cells that form the adult organism. This specialisation allows multicellular organisms to exploit resources more efficiently than single cells.<ref>{{cite book |first1=Bruce |last1=Alberts |first2=Dennis |last2=Bray |first3=Julian |last3=Lewis |first4=Martin |last4=Raff |first5=Keith |last5=Roberts |first6=James D. |last6=Watson |chapter=From Single Cells to Multicellular Organisms |title=Molecular Biology of the Cell |edition=3rd |location=New York |publisher=Garland Science |date=1994 |isbn=978-0-8153-1620-6 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK28332/ |access-date=12 June 2012 |url-access=registration |url=https://archive.org/details/molecularbiology00albe }}</ref> About 800 million years ago, a minor genetic change in a single molecule, the [[enzyme]] [[GK-PID]], may have allowed organisms to go from a single cell organism to one of many cells.<ref name="NYT-20160107">{{cite news |last=Zimmer |first=Carl |author-link=Carl Zimmer |title=Genetic Flip Helped Organisms Go From One Cell to Many |url=https://www.nytimes.com/2016/01/12/science/genetic-flip-helped-organisms-go-from-one-cell-to-many.html |date=7 January 2016 |work=[[The New York Times]] |access-date=7 January 2016 |url-status=live |archive-url=https://web.archive.org/web/20160107204432/http://www.nytimes.com/2016/01/12/science/genetic-flip-helped-organisms-go-from-one-cell-to-many.html |archive-date=7 January 2016 }}</ref> Cells have evolved methods to perceive and respond to their microenvironment, thereby enhancing their adaptability. [[Cell signalling]] coordinates cellular activities, and hence governs the basic functions of multicellular organisms. Signaling between cells can occur through direct cell contact using [[juxtacrine signalling]], or indirectly through the exchange of agents as in the [[endocrine system]]. In more complex organisms, coordination of activities can occur through a dedicated [[nervous system]].<ref name=alberts2002>{{cite book |first1=Bruce |last1=Alberts |first2=Alexander |last2=Johnson |first3=Julian |last3=Lewis |first4=Martin |last4=Raff |first5=Keith |last5=Roberts |first6=Peter |last6=Walter |chapter=General Principles of Cell Communication |title=Molecular Biology of the Cell |location=New York |publisher=Garland Science |date=2002 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK26813/ |access-date=12 June 2012 |isbn=978-0-8153-3218-3 |url-status=live |archive-url=https://web.archive.org/web/20150904000612/http://www.ncbi.nlm.nih.gov/books/NBK26813/ |archive-date=4 September 2015 }}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page