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Unit 3: Biodiversity and the interconnectedness of life
Quick questions on Population ecology: growth models, carrying capacity and life history (QCE Biology Unit 3)
12short 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 are 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 are limiting factors?Show answer
A limiting factor is any condition that restricts population growth.
What are 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 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 are density-dependent factors?Show answer
Their effect strengthens as population density rises. They produce negative feedback that pushes the population back toward K.
What are 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:
What is k-selected species?Show answer
Adapted to stable, predictable environments where competition near K matters. Traits include:
What is q1?Show answer
Distinguish between exponential and logistic growth models and identify two density-dependent limiting factors. [3 marks]
What is q2?Show answer
A population starts at 100, with a per capita growth rate of 0.1 per year. Calculate the size after 5 years under exponential growth, and explain why logistic growth predicts a lower value if carrying capacity is 200. [3 marks]
What is q3?Show answer
Refer to r-selected and k-selected species. (a) List three contrasting life-history traits. (b) Identify one Queensland example of each.