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Unit 3: Populations

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How can the shape of a population pyramid tell you whether a country will boom, hold steady, or shrink?

Topic 3.5 Age Structure Diagrams: interpret age structure diagrams (population pyramids) to predict population growth, stability or decline.
A focused answer to APES Topic 3.5, covering how to read age structure diagrams, the three pyramid shapes, the pre-reproductive, reproductive and post-reproductive cohorts, and how shape predicts future growth, with a worked pyramid-reading question.
9 min answer →

What sets the ceiling on how many organisms an environment can support, and what happens when a population shoots past it?

Topic 3.3 Carrying Capacity: define carrying capacity, explain overshoot and dieback, and interpret population oscillations around the carrying capacity.
A focused answer to APES Topic 3.3, covering the definition of carrying capacity, limiting factors, overshoot and dieback, oscillation around K, and the difference between density-dependent and density-independent factors, with a worked overshoot calculation.
10 min answer →

Why does population growth first surge and then slow as a country industrializes?

Topic 3.8 Demographic Transition: describe the four stages of the demographic transition model and explain how birth and death rates change as a country develops.
A focused answer to APES Topic 3.8, covering the four stages of the demographic transition model, how birth and death rates and growth change at each stage, the link to development and age structure, with a worked stage-identification question.
10 min answer →

Why does a raccoon thrive almost anywhere while a panda survives only where bamboo grows?

Topic 3.1 Generalist and Specialist Species: distinguish generalist from specialist species and explain how a changing or stable environment favors each.
A focused answer to APES Topic 3.1, covering the difference between generalist and specialist species, the role of niche breadth, and how stable versus changing environments favor each strategy, with a worked species-comparison question.
9 min answer →

What makes a human population grow, and how do birth, death and migration rates combine to set its growth rate?

Topic 3.7 Human Population Dynamics: explain the factors that influence human population size and growth, and calculate growth rate from crude birth, death and migration rates.
A focused answer to APES Topic 3.7, covering crude birth and death rates, immigration and emigration, the factors driving human population change, infant mortality and life expectancy, and how to calculate population growth rate, with worked math.
11 min answer →

When does a population explode in a J-shaped curve, and when does it level off in an S?

Topic 3.4 Population Growth and Resource Availability: compare exponential (J-curve) and logistic (S-curve) growth, link them to r- and K-selected species, and calculate growth rate and doubling time.
A focused answer to APES Topic 3.4, covering exponential and logistic growth, r- and K-selected species, the role of resource availability, and quantitative growth-rate and rule-of-70 doubling-time calculations, with worked math.
11 min answer →

Why do humans, songbirds and oysters each leave a differently shaped line on a survivorship graph?

Topic 3.2 Survivorship Curves: interpret Type I, II and III survivorship curves and link each shape to a species' reproductive and life-history strategy.
A focused answer to APES Topic 3.2, covering Type I, II and III survivorship curves, how each is read on a log scale, the species each describes, and how curve shape links to r- and K-selected strategies, with a worked curve-reading question.
9 min answer →

Why does a fertility rate of about 2.1 keep a population from growing or shrinking?

Topic 3.6 Total Fertility Rate: define total fertility rate and replacement-level fertility, and explain the factors that raise or lower a country's TFR.
A focused answer to APES Topic 3.6, covering total fertility rate, replacement-level fertility, the factors that change TFR (education, family planning, infant mortality, urbanization), and its link to population growth, with a worked replacement calculation.
10 min answer →