This chapter is crucial because it builds the core understanding of how populations grow, how resource limits and dispersal shape population size, and how interactions among organisms (competition, predation, metapopulation dynamics) determine survival and persistence. These concepts are frequently asked in board exams and competitive tests through calculations (growth rates, dispersion, life tables) and interpretation-based questions (Allee effect, metapopulation equilibrium, Lotka–Volterra outcomes).
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Minutes
10
Questions
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Marking
Q1. A population of rodents has intrinsic rate of increase , current population size , and carrying capacity . Using the logistic growth equation , the instantaneous population growth rate (individuals per year) is:
Q2. In a mark–recapture study the Lincoln–Petersen estimator is . A researcher marks beetles and later captures , of which are recorded as marked. It is later discovered that 20% of originally marked beetles had lost their marks before the second sampling (so some recaptured marked individuals were not recognized). Compared to the true population size, the estimated computed from the observed will most likely be:
Approximately unbiased (close to true population)
An underestimate of the true population size
Unclear without more data on capture probabilities
An overestimate of the true population size
Q3. The life-table for a species gives age-specific survivorship and fecundity as follows: age ; ; . Using , and , the intrinsic rate of increase (per year) is approximately:
Q4. In the Levins metapopulation model the equilibrium fraction of occupied patches is , where is the colonization rate and the extinction rate. If , what minimum colonization rate (in yr) is required to ensure at least () of patches remain occupied at equilibrium?
Q5. Two species interact via Lotka–Volterra competition. Competition coefficients are (effect of species 2 on 1) and (effect of species 1 on 2). Their carrying capacities in isolation are and . The model predicts stable coexistence if and . Given these values, the expected long-term outcome is:
Species 1 excludes species 2
Stable coexistence of both species
Species 2 excludes species 1
Outcome depends on initial densities (priority effect / bistability)
Q6. A population grows continuously according to the model . If and the initial population , the population size after days is closest to:
200 individuals
400 individuals
800 individuals
100 individuals
Q7. Using the life-table values below, calculate the net reproductive rate and choose the correct interpretation.
Age : 0, 1, 2, 3
: 1.0, 0.6, 0.3, 0.05
: 0, 1.2, 2.0, 1.6
; population will decline (each female produces <1 daughter).
; population will decline because high juvenile mortality offsets reproduction.
; population will remain approximately stable.
; population is expected to increase over generations (each female produces >1 daughter).
Q8. A field study sampled 10 equal quadrats and recorded individuals per quadrat: . Using the index of dispersion (where is variance and the mean), which dispersion pattern does this data indicate?
Random dispersion (index of dispersion )
Clumped (aggregated) dispersion (index )
Uniform (regular) dispersion (index )
Highly patchy with multiple modes (index )
Q9. Assertion (A): An Allee effect can create a critical population threshold below which a population tends to decline to extinction even when resources are abundant.
Reason (R): This effect occurs solely because predators preferentially target low-density populations, increasing per-capita mortality at small population sizes.
Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false but R is true.
Q10. In the Lotka–Volterra competition model the zero-growth isoclines are and . For two species the parameters are . Based on these values, which equilibrium outcome is predicted?
Stable coexistence of both species.
Competitive exclusion: species 1 will exclude species 2.
Competitive exclusion: species 2 will exclude species 1.
Unstable coexistence (priority effect); outcome depends on initial densities.