## Problem 327 — rank:208

**Title:** Evolutionary origin and ecological limits of nitrogen fixation

**Added binding assumptions (LaTeX):**

```latex
Compare growth at the same resident resource/community state and specify whether fixing is rare or allowed to reshape that state. An ecological advantage region is robust only where the minimum compatible growth difference is positive, not merely its fitted point estimate. Gene presence, enzyme homology and realized nitrogen-fixing function are distinct observations. Modern physiological feasibility does not uniquely identify an ancestral origin or transfer history.
```

**Direct edits:** 0. **Fresh external checks:** None; supplied sources retained as provenance.