Audit a lineage change across reproduction, movement and detection

1. Define the cross-scale claim

A population claim often passes through several stages before reaching a graph. Organisms contribute offspring, individuals move among populations, and observers detect only some of those present. A changed fraction in the final records can therefore combine biological change with an observation effect. A plausible adaptive story is not a substitute for reconstructing these stages.

2. Reconstruct the complete evidence chain

The original haploid two-lineage packet begins at true A frequency 0.4. Relative reproductive contribution is wA=a and wB=1, so the post-reproduction A frequency is 0.4a/(0.4a+0.6). A contribution greater than one is a relative weight, not a survival probability. Then a fraction m of the pool is replaced by migrants with A frequency 0.8, giving (1−m)p+0.8m.

Detection is 0.8 for A and 0.4 for B. Expected A and B records per true individual are therefore 0.8p and 0.4(1−p), and the observed A fraction divides the first by their sum. This final denominator differs from the true population denominator. Even the initial true frequency 0.4 yields observed A fraction 4/7 under unequal detection.

Connect the stages to earlier modules. Character and gene-tree evidence establish what the lineage labels mean, not their reproductive advantage. Plant nutrient/transport or animal physiological evidence could support a mechanism for differential contribution, while microbial partners could change that mechanism in context. Independent movement and detection records are still needed. Neither a functional trait nor a tree topology alone proves why the observed frequency changed.

3. Audit a worked original packet

At relative contribution 1.5 and replacement fraction 0.2, total weighted contribution is 1.2 and post-reproduction A frequency 0.5. Migration raises true frequency to 0.56. Expected detected A/B records are 0.448/0.176 per true individual, so observed A fraction is 28/39 ≈ 0.71795. These are three distinct stages, not one selection estimate.

4. Predict, compare and reject an explanation

Predict first: Can an observed lineage fraction overstate the true fraction without any additional reproductive change?

Compare neutral contribution/no migration with changed contribution only, migration only and both. Retain all denominators and a proposed independently measured stage-specific discriminator. Explain what a plant, microbial or animal mechanism would add beyond a lineage label.

5. Respond to an unfamiliar boundary

Apply the mechanism to a changed case

At relative contribution 1 and migrant replacement 0.4, find true A frequency after migration and its expected detected fraction.

Retain your calculation, units and assumptions in the lesson notebook before opening this public practice response.

Compare a worked response

True frequency is 0.6×0.4+0.4×0.8 = 0.56, and the detected fraction is again 28/39 ≈ 0.71795. This matches the worked final observation despite a different reproduction/migration history, demonstrating nonidentifiability from the final composition alone.

6. Preserve and defend independent reasoning

Use the General Biology II course workspace to retain a first cross-module report, criterion-linked human critique, justified revision and a reviewer-supplied new prompt/response. Separate authored coverage and public practice from actual supervised practical evidence, independently assessed reasoning and institutional equivalence. No organism handling, physiological intervention or field manipulation is requested.

Supporting method/mechanism reference, checked 30 October 2026. Original synthetic records and calculations, not a field study or copied source exercise.