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C4.1.6—Negative feedback control

Negative feedback control explains how ecological evidence links organisms, resources and interactions to population size, distribution or community structure in a habitat.

Syllabus
First assessment 2025
Objective
C4.1.6
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper3
Typical marks2

Common command terms

  • Identify
  • Explain

Scoring notes

Common mistake
Confusing a population with a community or with all organisms in an ecosystem.

Recent exam appearances

May 2023Paper3 ["HL"] · TZ116(b)[ 2 ]C4.1.6—Negative feedback control
Practice this objective

Coverage 2023–2023 · Updated 16 Jul 2026

Negative feedback restrains population growth

Negative feedback restrains population growth.

As density rises, competition, disease or predation can reduce births or increase deaths. The response opposes the change and tends to return population size toward a range.

disturbance → density-dependent response → birth/death change → correction.

Crowding increases disease transmission, lowering survival and slowing further population growth.

Not every population change is negative feedback; density-independent storms can reduce numbers without crowding.

Negative feedback control

Assessment in practice

1–2 marks
How it is assessed

This objective is assessed through structured response, commonly using Identify / Explain.

Command terms

Identify / Explain

What earns marks

Build the answer around this relationship: Negative feedback control must be linked to the correct ecological unit, method or species interaction.

Watch for

Confusing a population with a community or with all organisms in an ecosystem.

Representative question

Question 1

[Maximum number: 2]

Explain the change in numbers of the cactus moth throughout the study period.

Populations and Communities

  • A population is one species in an area; a community is all interacting populations there.
  • Estimate abundance with unbiased sampling: quadrats for sessile organisms and capture–mark–release–recapture for mobile animals, checking each method’s assumptions.
  • Density-dependent competition, predation, disease and waste create negative feedback around carrying capacity; exponential growth slows into a sigmoid curve as limits strengthen.
  • Classify interspecific relationships by costs and benefits: predation, herbivory, competition, mutualism, parasitism and pathogenicity.
  • Invasive species may escape controls and displace endemic species. Removal experiments can reveal competition and fundamental versus realized niches.
  • Chi-squared tests assess species association from observed and expected quadrat counts.
  • Predator peaks usually lag prey peaks; top-down control begins with consumers, while bottom-up control begins with resources or producers.

Concept essentials

  • Negative feedback control must be linked to the correct ecological unit, method or species interaction.
  • The evidence for negative feedback control depends on measurable abundance, distribution, survival or resource patterns.
  • Negative feedback control is clearest when cause, ecological process and population outcome are kept distinct.
  • Field or graph evidence for negative feedback control needs biological interpretation, not values alone.
ConceptIB Biology HL