Network analysis in biology
Biological systems are often represented as networks which are complex sets of binary interactions or relations between different entities. Essentially, every biological entity has interactions with other biological entities, from the molecular to the ecosystem level, providing us with the opportunity to model biology using many different types of networks such as ecological, neurological, metabolic or molecular interaction networks (Figure 1).
The data explosion that originated in the -omics era of biological research necessitated the development of more systemic approaches to data analysis and a move away from the single gene/protein perspective. Systems biology aims to understand biological entities at the systemic level, analysing them not only as individual components, but also as interacting systems and their emergent properties. Related to this is network biology which allows the representation and analysis of biological systems using tools derived from graph theory.
Figure 1 Networks can be used to model many types of biological data.
The next section introduces some of the key concepts of graph theory and how they apply to biological networks.