A modular system can be separated into units that perform almost independently - Roland Krause

Most networks we can imaginge are not modular - Roland Krause

Optimal systems are not modular - Roland Krause

Biology is modular, we would not understand it without modules - Roland Krause

Network motifs exist - Roland Krause

Evolutionary models use computers to evolve networks towarrds a goal. Initial population - select - mutate - reproduce, select etc. Systems evolved in this way (Neural networks digital systems) tend not to be modular with no network motifs. - Roland Krause

How can evolution produce modularity and network motifs? - Roland Krause

A toy problem of circuits with NAND gates is evolved by rewiring. The desired output is (X XOR Y) AND (Z OR W) as a fitness goal. The solution is typically small and non-modular. - Roland Krause

Engineers (software e.) use modules, simple systems that work and can be re-used, including re-wiring. - Roland Krause

Goals change over time. Switch a goal every 20 generations with common sub-problems: Modularly varying goals. Organisms will evolve to a state that they can re-wire quickly to respond to goals. They display a modular structure.. - Roland Krause

The circuits discover the hidden modularity of the goals. They also exhibit network motifs. - Roland Krause

Scales well with problem size. - Roland Krause

What happens when goals become fixed? The modularity is lost. Modular solution use additional gates, are larger. - Roland Krause

Modular systems (with swtching goals) evolve faster than fixed goals systems. The speed up by modular systems increase with a power law. - Roland Krause

The extinction 60 millions ago left a early mouse-like mammal that evolved quickly into whales and primates etc, much quicker than a computer simulation would expect. - Roland Krause

Evolution under constant environments is typically slow. Modular solutions work well in a fitness landscape - not simulated annealing but changing goals. - Roland Krause

Modules (goals) exist on organismal, cellular, protein levels. If the goals is constant, it should not be modular. Ribosomal proteins have fixed goal and are therefore not modular (Yanai & Lancet, Trends in Genetics) - Roland Krause

Parter, Kashtan, Alon, BMC Evol Biol 2007. Bacterial metabolic networks are modular for complex environments, simple for parasites. - Roland Krause

Great talk, sitting in a lecture theater on Saturday at 9am never was so useful. - Roland Krause

Q: Speed up for multi-cellular organisms? Does each cell type face different goals. A: Proteins in eukaryotes are more modular. And yes. - Roland Krause

Q: Application to yeasts - which growth conditions are modular? A. Sugars might vary, TCA cycle is constant. Modules for metabolizing different sugars. - Roland Krause

Q. Do modern organisms loose modularity? Should conserved elements be more or less modular? A: Not being explored yet, interesting field of research. - Roland Krause

Q: Chemostat data, 1000 generations are possible. Do we see loss of modularity? A: 1000 generations will only see one or two modules decreasing. Chemostat not explored. E coli and Buchnera show the difference more expressed by loosing modules. - Roland Krause

Q: Relationship between goals and modules: Frequency of goal switching .A: Large range of goals switching times show modularity. - Roland Krause

A recent article on the matter, which includes some of the aspects of the talk (and much more) http://www.ploscompbiol.org/article... - Roland Krause