Essays and notes on biology & living systems.
Engineers can recognize boundaries, state, resource budgets, signaling and feedback loops. The membrane behaves a little like an interface, except the interface is physical material that the cell continuously builds,…
Regulation weakens simplistic genetic determinism: possessing information is not equivalent to using…
Looking at present-day outcomes can tempt us to imagine an earlier plan, as if evolution knew a future goal and accumulated changes to reach it. Natural selection should not be treated as a human product-planning process.
Humans live with large communities of microorganisms on and inside the body. These communities interact with digestion, immune development, metabolism and environmental exposure, and they change with diet, age,…
From early respiration experiments through the mapping of biochemical cycles, metabolism became visible as an interconnected network rather than isolated…
Molecular biology made information language enormously productive, but gene regulation, developmental biology and cell biology showed why sequence alone cannot explain…
The factory metaphor imports hierarchy, departments and a manager. Cellular processes are entangled, molecules serve multiple roles, and the distinction between machinery and product is much less clean than in a…
Immunity is layered: physical barriers, sensing, innate responses, adaptive recognition, memory and regulation. The system must respond strongly enough to threats while tolerating self and many harmless or beneficial…
Experimental embryology, reaction-diffusion models and modern regulatory biology progressively replaced simple blueprint pictures with dynamic models of pattern…
Life is not merely organized matter; it is organized matter sustained by…
Living systems regulate many variables within viable ranges while conditions change. Sensors, signaling, opposing processes, anticipation and nested feedback loops contribute to temperature, glucose, gas exchange, fluid…
A compiled binary assumes a comparatively stable machine model. Proteins are part of a medium in which machine, component and environment are all physical and mutually…
A software architect can use the code metaphor to notice persistence, copying, interfaces and interpretation. The stronger model, however, is a running stateful system in which the genome is one durable information…
Homeostasis suggests that persistence can be an activity rather than a…
Control theory gives useful language for sensed variables, gain, delay, overshoot and feedback. It helps explain why stability can require continuous…
Engineers think in budgets: CPU, memory, bandwidth and power. Metabolism is a more radical budget because the system must acquire and transform the material from which its own machinery is…
The microbiome makes individuality porous: a human body is also…
The analogy fails if it suggests a clean software/hardware split, a single compiler, or a complete standalone specification of an organism. A DNA molecule outside a living cellular context does not boot…
A software product depends on services and libraries it does not fully own. The microbiome similarly complicates the picture of an organism as a completely self-contained…
Feedback means using an outcome to influence future input, but the presence of a feedback loop does not guarantee graceful stability. Direction, gain, and delay all matter.
DNA is a chemically stable information-bearing polymer, but sequence becomes biologically consequential only inside a cell that can copy, transcribe, regulate and interpret it. Protein-coding regions are only part of…
A deployment plan starts with an externally specified target. Development helps create both the structure and many of the conditions that guide subsequent steps; execution and construction of the 'plan' are…
Claude Bernard's idea of the internal milieu and Walter Cannon's later language of homeostasis made active regulation central to…
Immunology grew from observations of acquired protection into cellular and molecular models of recognition, clonal selection and…
Proteins remind us that information must become physical organization before it can do…
Software dependencies have package boundaries. Host and microbial systems exchange metabolites and influence one another in ways that make the system/environment boundary much less…
A systems architect sees a distributed coordination problem: local agents respond to local state while a reproducible large-scale form…
Engineers recognize policy violations, resource contention and local components whose behavior no longer aligns with whole-system goals. Cancer makes that coordination problem…
The cell demonstrates that coherent organization does not automatically imply a central…
Cancer exposes the price of multicellular cooperation: billions of cells must keep respecting constraints on growth and…
Computer security often assumes cleaner boundaries between system and attacker. Biology contains symbionts, changing tissues and molecular resemblance between self and…
Cancer research moved from organ-level pathology to cellular, genetic, immunological and evolutionary explanations; none of those levels alone is…
A thermostat analogy becomes misleading when it implies one fixed set point. Biological targets, controllers and acceptable ranges can change with development, exercise, illness and…
Cell theory established cells as fundamental units of life; molecular biology later focused attention on genes, while modern systems and physical biology increasingly emphasize interactions and…
A scheduler allocates resources that already exist inside a machine. Metabolism creates, stores, transforms and disposes of the physical resources that constitute the living machine…
Engineers know that code existing in a repository is different from code executing in production. Gene regulation offers a related distinction between capability, activation and…
An engineer can think about proteins as active components with interfaces and state, but their interfaces are molecular surfaces whose shapes, charge and energies change with…
Feature flags are intentionally designed and usually binary enough to audit. Biological regulation is evolved, overlapping, noisy, graded and deeply coupled to the physical state of the…
Gene regulation controls when, where and how strongly genes are expressed. Transcription factors, DNA accessibility, chromatin state, RNA processing, signaling and cellular history all contribute to whether a sequence…
A cell is a bounded, energy-consuming chemical system that maintains gradients, repairs components, senses conditions, changes gene expression, recycles material and reproduces. Coordination is distributed across…
Cancer involves cells acquiring changes that alter growth, survival, interaction and tissue control. Tumors can contain diverse populations that compete, cooperate and respond differently to…
A runaway process does not evolve a population of descendants inside the computer. Tumors do: mutation, selection, tissue ecology and immune interaction all…
Work on gene regulation transformed the old one-way picture of genes issuing instructions into a layered view of conditional expression and…
Structural biology connected linear sequence to three-dimensional molecular form and made it clear that sequence alone is not a complete description of…
After germ theory transformed medicine through the study of pathogens, microbiome research made coexistence and ecological interaction equally important…
Proteins begin as amino-acid chains, but their biological roles depend on folding, chemical modification, concentration, location, binding partners and the surrounding physical conditions. Sequence constrains function…
Development emerges from cell division, gene regulation, positional signals, mechanical forces, cell movement and communication among neighboring cells. A body is constructed through interacting processes rather than by…
DNA turns the philosophical question of information into a physical one: when does a persistent pattern become meaningful to a…
Development asks how global form can arise when no individual cell contains a complete map of the…
Metabolism is the connected web of chemical transformations through which organisms acquire usable energy, build molecules, recycle components and maintain internal conditions. Life continually couples energy flow to…
Security engineering contributes useful questions about identity, anomaly detection, layered defense, false positives and memory under…
Information, response, and control inside a cell can remind us of computing. The analogy can help frame some questions, but similarity does not make the two systems identical.
Immunity shows that biological identity is partly maintained by active, continuous…
Alternate paths can keep a system working after one path fails, but redundancy has a cost. Space, energy, and control requirements grow with it. Reliability is therefore also a resource question.