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QLDBiologyQuick questions
Unit 3: Biodiversity and the interconnectedness of life
Quick questions on Population ecology: growth models, carrying capacity and life history (QCE Biology Unit 3)
15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is population growth models?Show answer
Exponential growth. When resources are unlimited and there is no significant predation, disease or competition, each individual produces, on average, more than one surviving offspring per generation. The result is a J-shaped curve.
What is limiting factors?Show answer
A limiting factor is any condition that restricts population growth.
What is survivorship curves?Show answer
A survivorship curve plots the proportion of a cohort surviving (log scale on the y-axis) against age. Three idealised shapes exist.
What is r-selected and k-selected species?Show answer
The r and k labels come from the population models: r is per capita growth rate, K is carrying capacity. The strategies are best treated as ends of a continuum, not strict categories.
What is worked example?Show answer
Cane toads were introduced in Queensland in 1935 and have spread west and south.
What is exponential growth?Show answer
When resources are unlimited and there is no significant predation, disease or competition, each individual produces, on average, more than one surviving offspring per generation. The result is a J-shaped curve.
What is logistic growth?Show answer
Resources are finite. As N rises, per capita resources fall, birth rate declines and death rate rises. Growth slows and the population plateaus at the carrying capacity (K).
What is carrying capacity?Show answer
The maximum population size that the environment can sustain indefinitely with the available resources (food, water, shelter, breeding sites, oxygen). K is not a fixed property of a species; it varies with the environment and can shift seasonally or in response to long-term change.
What is density-dependent factors?Show answer
Their effect strengthens as population density rises. They produce negative feedback that pushes the population back toward K.
What is density-independent factors?Show answer
Their effect is the same proportion of individuals regardless of density.
What is r-selected species?Show answer
Adapted to unstable, unpredictable environments where rapid colonisation pays off. Traits include: - Small body size. - Short generation time.
What is k-selected species?Show answer
Adapted to stable, predictable environments where competition near K matters. Traits include: - Large body size. - Long generation time.
What is drawing exponential and logistic curves without labels?Show answer
Mark axes (N and t), the carrying capacity line and the inflection point of the logistic curve.
What is calling competition density-independent?Show answer
Intraspecific competition is the textbook density-dependent factor.
What is treating density-dependent and density-independent as mutually exclusive?Show answer
Real populations experience both. A bushfire (density-independent) reduces N, then density-dependent factors regulate the recovery toward K.