Editing Graph theory (section)

=== Biology ===
Likewise, graph theory is useful in [[biology]] and conservation efforts where a vertex can represent regions where certain species exist (or inhabit) and the edges represent migration paths or movement between the regions. This information is important when looking at breeding patterns or tracking the spread of disease, parasites or how changes to the movement can affect other species.

Graphs are also commonly used in [[molecular biology]] and [[genomics]] to model and analyse datasets with complex relationships. For example, graph-based methods are often used to 'cluster' cells together into cell-types in [[Single-cell_analysis#Transcriptomics|single-cell transcriptome analysis]]. Another use is to model genes or proteins in a [[Biological pathway|pathway]] and study the relationships between them, such as metabolic pathways and gene regulatory networks.<ref>{{cite journal | last1=Kelly | first1=S. | last2=Black | first2=Michael | title=graphsim: An R package for simulating gene expression data from graph structures of biological pathways | journal=Journal of Open Source Software | publisher=The Open Journal | volume=5 | issue=51 | date=2020-07-09 | issn=2475-9066 | doi=10.21105/joss.02161 | page=2161| bibcode=2020JOSS....5.2161K |biorxiv=10.1101/2020.03.02.972471|s2cid=214722561| doi-access=free | url=https://www.biorxiv.org/content/biorxiv/early/2020/06/30/2020.03.02.972471.full.pdf }}</ref> Evolutionary trees, ecological networks, and hierarchical clustering of gene expression patterns are also represented as graph structures. 

Graph theory is also used in [[connectomics]];<ref>{{Cite journal|last1=Shah|first1=Preya|last2=Ashourvan|first2=Arian|last3=Mikhail|first3=Fadi|last4=Pines|first4=Adam|last5=Kini|first5=Lohith|last6=Oechsel|first6=Kelly|last7=Das|first7=Sandhitsu R|last8=Stein|first8=Joel M|last9=Shinohara|first9=Russell T|date=2019-07-01|title=Characterizing the role of the structural connectome in seizure dynamics|journal=Brain|language=en|volume=142|issue=7|pages=1955–1972|doi=10.1093/brain/awz125|pmid=31099821|issn=0006-8950|pmc=6598625}}</ref> nervous systems can be seen as a graph, where the nodes are neurons and the edges are the connections between them.