Version 2 — revised in response to an external structural review and an automated critique pass. See "Response to Review" appendix in the PDF for the change log.A candidate reading of recent preprints in molecular network biology, population ecology, and genomics reveals a structural pattern worth investigating: biological systems across scales appear to operate under layered constraint hierarchies in which elemental stoichiometry, network topology, and slow epigenetic dynamics each independently filter the accessible regions of biological state space, and their combined action may explain the characteristic sparseness, modularity, and bistability observed in living systems. This is a heuristic reading, not a formal derivation from a shared mathematical framework. The synthesis draws on seven primary sources spanning q-bio.MN, q-bio.PE, q-bio.GN, and q-bio.BM. From q-bio.BM, elemental stoichiometry is proposed as an ecological biosignature because life occupies a statistically narrow, heteroatom-enriched region of an estimated 10⁶⁰-compound chemical space [corpus:arxiv:2605.19252]; the abstract notes that realising this as a discriminatory tool requires standardised methods for data collection not yet fully developed. From q-bio.MN, metabolic networks in marine microbiomes show modularity excess over null models of approximately ΔQ ~ 0.15–0.40, consistent with cost-minimization principles [corpus:arxiv:2605.05254]; autocatalytic network formalisms (RAF sets and stoichiometric autocatalysis) are shown to be mathematically less disparate than previously assumed, with the proof establishing that any RAF is stoichiometrically autocatalytic but not necessarily the converse [corpus:arxiv:2605.25523]; and DNA methylation is recast as a slow dynamical coordinate that autonomously reshapes expression landscapes rather than merely stabilizing them, based on minimal ODE and stochastic simulation models whose genome-scale generality is open [corpus:arxiv:2605.14562]. From q-bio.GN, renormalization-group-inspired extraction of transcription-factor binding sites reveals condition-dependent regulatory architectures [corpus:arxiv:2605.19071]. From q-bio.PE, interaction strengths in ecological communities follow a skewed-weak, Pareto-tailed-strong (SWAPS) distribution whose emergence accompanies increases in diversity and complexity [corpus:arxiv:2605.17220]. From q-bio.MN, topological data analysis of cancer protein networks identifies structurally relevant driver genes through persistent homology [corpus:arxiv:2605.11450]. The central falsifiable claim is that the three constraint layers—elemental composition, network modularity excess, and slow epigenetic dynamics—are not independent: elemental constraints on catalytic chemistry should predict the boundary conditions within which modularity excess and methylation-mediated landscape reshaping are physically achievable. A concrete falsification path is named in each synthesis subsection. The ecological-scale SWAPS bridge is treated as a weakly-connected addendum rather than a main synthesis finding. ---Authorship: Saluca Agentic AI Research Team (Saluca LLC). AI-drafted from arXiv preprint corpus on the date in the filename.Cited arXiv preprints: 2605.05254, 2605.07433, 2605.11450, 2605.14562, 2605.16781, 2605.17220, 2605.19071, 2605.19252, 2605.21945, 2605.25523, 2605.29958