Modularity in Biological Systems
Biological systems are often organized into interacting subsystems whose components work together more closely with one another than with the system as a whole.
The Investigative Question
Why are biological systems frequently organized into modules?
What We Observe
Genes, proteins, signaling pathways, metabolic pathways, anatomical structures, and developmental processes can form recognizable functional groupings.
Scientific Background
Modularity can reduce unwanted interactions, allow components to be reused in different contexts, and permit parts of a system to change without disrupting every other part.
Why It Matters
Modular organization can contribute to robustness, adaptability, and the evolution of complex systems.
What Is Known
Network analysis and experimental biology have identified modular organization in many cellular and developmental systems, although module boundaries are not always sharp.
What Is Proposed
Evolutionary models investigate how modularity can arise through duplication, selection, changes in network connectivity, and historical constraints.
What Remains Uncertain
Biological systems are highly interconnected, so describing a system as modular can depend upon the scale and criteria used to define the modules.
Design Relevance
Modularity resembles an important principle of human engineering. Its design relevance depends upon whether the biological pattern contains features that distinguish purposeful modular construction from modularity produced through evolutionary processes.
Assessment
Modularity is a useful and measurable feature of many biological systems, but its existence alone does not determine how those systems originated.