IB Biology SL C4.1 Populations and Communities Questions

Practise IB Biology SL C4.1 by estimating populations, reading community and growth data, and testing species interactions with quadrat and statistical evidence.

Exam points

Define a population and community, distinguish same-species from multi-species groupings, and interpret richness, abundance, or distribution data.
Use random quadrats or transects to estimate sessile populations, scaling representative counts by quadrat and habitat area.
Estimate a mobile-animal population with capture-mark-release-recapture, applying N = n₁ × n₂ / n₃ and its assumptions.
Relate carrying capacity to limiting resources and explain how density-dependent pressures regulate population growth.
Interpret exponential or sigmoid growth data, label growth phases, and explain slowing or plateaus through limiting factors.
Use behavioural or resource-distribution evidence to explain cooperation and competition within a species.
Classify interspecific relationships from their effects on each species, including competition, predation, parasitism, and mutualism.
Explain mutualism through exchanged resources or protection and identify benefits to both species in examples.
Distinguish endemic from invasive species and evaluate effects of invasive populations on native species and biodiversity.
Test interspecific competition or species association using ecological observations and chi-squared expected counts, degrees of freedom, and critical values.
Interpret predator-prey data to explain changing populations, foraging, and time-lagged effects.
Trace top-down control through a food web and predict trophic-cascade effects when a predator is removed.
Explain how a named plant's allelochemicals inhibit the germination or growth of neighbouring plants.

Covered syllabus points

C4.1.1—Populations C4.1.2—Population size estimation C4.1.3—Random quadrat sampling C4.1.4—Capture-mark-release-recapture C4.1.5—Carrying capacity C4.1.6—Negative feedback control C4.1.7—Population growth curves C4.1.8—Modelling sigmoid growth C4.1.9—Competition vs. cooperation C4.1.10—Community C4.1.11—Interspecific relationships C4.1.12—Mutualism as interspecific relationship C4.1.13—Endemic vs. invasive species C4.1.14—Tests for interspecific competition C4.1.15—Chi-squared test C4.1.16—Predator-prey relationships C4.1.17—Top-down vs. bottom-up control C4.1.18—Allelopathy and antibiotics

[Maximum number: 1]

What is a population?

Organisms of the same genus living in an ecosystem

Organisms living together and interacting in the same habitat

Organisms of a species living together in the same area

Organisms that can breed together

[Maximum number: 1]

In an area of forest measuring 100 m by 100 m , samples were taken to estimate the number of silver maple (Acer saccharinum) trees in the forest. The number of trees counted in each of five areas of $400 \mathrm{~m}^{2}$ was recorded.

Approximately how many silver maple trees are in the $10000 \mathrm{~m}^{2}$ area of forest?

125

625

[Maximum number: 2]

A school football field has plantain plants (Plantago media) growing on it as well as grass. Each plantain plant has a short stem with a circle of wide leaves. Outline how the size of the plantain population could be estimated using a quadrat method.

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Covered syllabus points

Question 1

Question 2

Question 3