Editing Evolutionary developmental biology (section)

===Developmental bias===
{{Main|Developmental bias}}

[[File:Chilipoda- Geophilomorpha (3309242471).jpg|thumb|Among the [[centipede]]s, all members of the [[Geophilomorpha]] are constrained by a developmental bias to have an odd number of segments, whether as few as 27 or as many as 191.]]

Development in specific lineages can be biased either positively, towards a given trajectory or phenotype,{{efn|Positive bias is sometimes called developmental drive.<ref name=Arthur2001/>}} or negatively, away from producing certain types of change; either may be absolute (the change is always or never produced) or relative. Evidence for any such direction in evolution is however hard to acquire and can also result from developmental constraints that limit diversification.<ref name="Drost 2017 69–75"/> For example, in the [[gastropod]]s, the snail-type shell is always built as a tube that grows both in length and in diameter; selection has created a wide variety of shell shapes such as flat spirals, [[cowrie]]s and tall turret spirals within these constraints. Among the [[centipede]]s, the [[Lithobiomorpha]] always have 15 trunk segments as adults, probably the result of a developmental bias towards an odd number of trunk segments. Another centipede order, the [[Geophilomorpha]], the number of segments varies in different species between 27 and 191, but the number is always odd, making this an absolute constraint; almost all the odd numbers in that range are occupied by one or another species.<ref name="Arthur2001">{{Cite journal |last=Arthur |first=W. |date=July 2001 |title=Developmental drive: an important determinant of the direction of phenotypic evolution |journal=Evolution & Development |volume=3 |issue=4 |pages=271–278 |doi=10.1046/j.1525-142x.2001.003004271.x |pmid=11478524 |s2cid=41698287}}</ref><ref name="Arthur2002Centipedes">{{Cite journal |last=Arthur |first=W. |date=October 2002 |title=The interaction between developmental bias and natural selection: from centipede segments to a general hypothesis |journal=Heredity |volume=89 |issue=4 |pages=239–246 |doi=10.1038/sj.hdy.6800139 |pmid=12242638 |doi-access=free}}</ref><ref name="ChipmanArthurAkam2004">{{Cite journal |last=Chipman |first=Ariel D. |last2=Arthur |first2=Wallace |last3=Akam |first3=Michael |date=July 2004 |title=A Double Segment Periodicity Underlies Segment Generation in Centipede Development |journal=Current Biology |volume=14 |issue=14 |pages=1250–1255 |doi=10.1016/j.cub.2004.07.026 |pmid=15268854 |s2cid=2371623 |doi-access=free}}</ref>