KHAEMENES ACADEMY · BIOLOGY 10 · WEEK 32 · DAY 04

Human Perturbation, Feedback & System Response

Use flux diagrams to analyze how altered rates can change reservoirs, feedbacks and downstream ecosystems.

Safety and evidence boundary

Use public system diagrams and aggregate environmental data. Field observations must remain non-contact and safe. Do not enter hazardous water, drains, industrial sites, disaster areas, or collect protected materials. Distinguish measured fluxes from arrows drawn in a model.

Explicit science instruction

Humans change cycles through fossil-fuel combustion, fertilizer use, wastewater, land conversion, dams, mining and altered fire regimes. A perturbation changes one or more fluxes; the system response depends on reservoir size, feedbacks, delays and nonlinear thresholds.

Feedback can amplify or reduce change, but feedback direction and strength must be demonstrated rather than assumed.

Worked example with reasoning

A watershed fertilizer input rises by 40 units/year while downstream biological uptake increases only 10 and export increases 25. The remaining 5 units/year accumulate in the simplified budget. Over time that storage can alter future fluxes.

Guided question

Why can a system continue changing after an external input stops?

Independent work

  1. Balance a perturbed nutrient budget.
  2. Identify one delayed reservoir.
  3. Propose a negative and a positive feedback.
  4. State evidence needed to verify each.

Investigation / Data Lab

Coupled carbon–nitrogen systems model

Question: How does changing one flux alter storage and linked nutrient cycling in a bounded ecosystem model?

  1. Build a box-arrow model with atmosphere/water, producer biomass, consumer biomass, detritus/soil, and at least one inorganic nutrient pool.
  2. Assign units to every reservoir and flux.
  3. Calculate one baseline mass balance, then change a single human-driven flux.
  4. Track which reservoirs accumulate or decline over three modeled intervals.
  5. Add one feedback hypothesis and identify the evidence needed to validate it.

Evidence standard: preserve the baseline and perturbed diagrams, calculations, boundary, and feedback uncertainty.

Misconception check

A feedback arrow in a diagram is a hypothesis about causal response unless supported by measurements or validated models.

Formative understanding check

If inputs exceed outputs, what happens to reservoir size in a simple mass balance?

Worked response

It increases.

Open-book formative practice only; not an official mastery attempt or grade.

Mentor evidence conference

Ask Archaemenes to challenge your systems model, quantitative interpretation, alternative explanations, and boundary conditions.

Open Archaemenes

Teacher guidance

Foundation: use input-output tables. Core: calculate accumulation and delays. Extended: analyze threshold behavior and management lag.

Preserve learning evidence

Keep models, calculations, graphs, corrections and uncertainty notes in the matching Week 32 evidence field.