Population Dynamics — Flashcards & Quiz

Q1: Distinguish between exponential growth and logistic growth in populations.

Exponential growth (J-curve) occurs when resources are unlimited — the population grows without constraint at a constant rate (dN/dt = rN). Logistic growth (S-curve) occurs when resources are limited — growth slows as the population approaches the carrying capacity (K), where birth rate equals death rate: dN/dt = rN((K−N)/K).

Q2: What is carrying capacity and what factors determine it?

Carrying capacity (K) is the maximum population size that an environment can sustain indefinitely given available resources. It is determined by limiting factors: density-dependent factors (competition, predation, disease, parasitism — intensify as population grows) and density-independent factors (natural disasters, climate events, fire — affect populations regardless of size).

Q3: Explain the difference between r-selected and K-selected species.

r-selected species: high reproductive rate, many small offspring, little parental care, short lifespan, rapid maturity, thrive in unstable environments (e.g. insects, weeds, bacteria). K-selected species: low reproductive rate, few large offspring, significant parental care, long lifespan, late maturity, thrive in stable environments near carrying capacity (e.g. elephants, whales, humans).

Q1: Exponential population growth can continue indefinitely in any environment.

Answer: FALSE

Exponential growth cannot continue indefinitely because resources are finite. Eventually, limiting factors (food, space, water, disease, predation) slow growth, and the population approaches its carrying capacity — resulting in logistic growth.

Q2: Carrying capacity is the maximum population size an environment can sustain indefinitely.

Answer: TRUE

Carrying capacity (K) represents the maximum number of individuals an environment can support long-term, given its available resources. The population fluctuates around K as conditions change.

Q3: Disease and competition are examples of density-independent limiting factors.

Answer: FALSE

Disease and competition are density-DEPENDENT limiting factors — their effects intensify as population density increases. Density-independent factors (e.g. bushfire, drought, flood) affect populations regardless of their size.