Population Ecology and Growth Practice Questions
20 free Population Ecology and Growth practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
In the exponential growth model (dN/dt = rN), what does the variable 'r' represent?
- A Total population size
- B Carrying capacity of the environment
- C Intrinsic rate of natural increase
- D Number of individuals added per unit time
Correct answer: Intrinsic rate of natural increase
The variable 'r' is the per capita rate at which a population increases when resources are unlimited. It is calculated as the birth rate minus the death rate (b - d).
Which of the following conditions is required for a population to exhibit a J-shaped growth curve?
- A High predation and disease levels
- B Limited food and water availability
- C Abundant resources, no competition
- D A stable age distribution structure
Correct answer: Abundant resources, no competition
A J-shaped curve represents exponential growth, which occurs when a population has abundant resources and no competition limiting it. This typically happens when a species colonizes a new, favorable environment with no environmental resistance.
The maximum population size that a particular environment can sustain over a long period is known as the:
- A Biotic potential
- B Environmental resistance
- C Carrying capacity
- D Threshold density
Correct answer: Carrying capacity
Carrying capacity (K) is determined by limiting factors such as food, water, and nesting sites. When a population reaches K, the growth rate becomes zero as births equal deaths.
In the logistic growth equation dN/dt = rN[(K-N)/K], what happens to the growth rate as N approaches K?
- A The growth rate increases exponentially
- B The growth rate remains constant
- C The growth rate declines toward zero
- D The growth rate becomes negative
Correct answer: The growth rate declines toward zero
As the population size (N) nears the carrying capacity (K), the term (K-N)/K becomes smaller. This mathematically reduces the overall growth rate until it levels off at the carrying capacity.
An age-structure diagram (population pyramid) with a very wide base indicates that the population is:
- A Stable
- B Declining
- C Growing rapidly
- D Exceeding its carrying capacity
Correct answer: Growing rapidly
A wide base means there is a high proportion of young individuals in the pre-reproductive age group. As these individuals move into reproductive age, the population is expected to grow significantly.
Which type of survivorship curve is characteristic of species that produce many offspring but provide little or no parental care (e.g., many fish and marine invertebrates)?
- A Type I
- B Type II
- C Type IV
- D Type III
Correct answer: Type III
Type III curves show very high mortality rates for the young, but mortality levels off for the few individuals that survive to adulthood. This strategy relies on sheer numbers to ensure some offspring survive.
Which of the following is a density-independent factor that limits population growth?
- A Infectious disease
- B Interspecific competition
- C Accumulation of toxic waste
- D A severe forest fire
Correct answer: A severe forest fire
Density-independent factors affect a population regardless of its size or density. Natural disasters like fires, floods, or extreme temperature shifts kill individuals without regard to how many are in the area.
The sum of all limiting factors that prevent a population from reaching its biotic potential is called:
- A Environmental resistance
- B Intrinsic rate of increase
- C Net reproductive rate
- D Natural selection pressure
Correct answer: Environmental resistance
Environmental resistance includes both biotic factors (like predation and disease) and abiotic factors (like drought) that limit growth. It is the force that turns an exponential curve into a logistic one.
Species that follow a 'K-selection' strategy generally exhibit which of the following traits?
- A Small body size and short lifespan
- B Production of many small offspring
- C Rapid development and early reproduction
- D High parental care and stable population
Correct answer: High parental care and stable population
K-selected species thrive in stable environments near the carrying capacity. They focus on quality over quantity, producing fewer offspring and providing significant care to ensure survival.
A population that shows a constant mortality rate throughout the lifespan of the individuals exhibits which survivorship curve?
- A Type I
- B Type II
- C Type III
- D Type IV
Correct answer: Type II
In a Type II curve, the probability of dying is the same at every age. This is often seen in organisms like songbirds, hydra, and some lizards.
Semelparity refers to a reproductive strategy where an organism:
- A Produces offspring repeatedly throughout its lifetime
- B Produces all offspring in a single reproductive event
- C Only reproduces when the population density is low
- D Produces only a single offspring per reproductive cycle
Correct answer: Produces all offspring in a single reproductive event
Semelparity (or 'big-bang' reproduction) is seen in species like Pacific salmon or century plants. They invest all their energy into one massive reproductive effort and usually die shortly after.
The statistical study of populations, including their size, structure, and distribution over time, is called:
- A Ethology
- B Demography
- C Biogeography
- D Tectonics
Correct answer: Demography
Demography uses mathematical tools to investigate how populations change. Key parameters include birth rates, death rates, and life expectancy.
In a population of 1000 squirrels, there are 40 births and 10 deaths in a year. What is the annual per capita growth rate (r)?
- A 0.03
- B 0.30
- C 0.04
- D 0.05
Correct answer: 0.03
Growth rate (r) is (Births - Deaths) / Total Population. (40 - 10) / 1000 = 30/1000 = 0.03.
When a population's size (N) is much smaller than the carrying capacity (K), the logistic growth model behaves most like:
- A A declining population
- B A stable population size
- C Zero population growth
- D Near-exponential growth
Correct answer: Near-exponential growth
When N is small, (K-N)/K is nearly 1. This means the limiting effects of the environment are negligible, and the population grows at a rate nearly equal to its intrinsic potential.
Which of the following describes a 'r-selected' species?
- A A dandelion producing thousands of seeds
- B A whale that matures late and has one calf
- C An elephant that lives in a stable herd
- D A human living in a developed country
Correct answer: A dandelion producing thousands of seeds
r-selected species are adapted to unstable or unpredictable environments. They maximize reproductive success by producing large numbers of offspring quickly, with little investment in each.
If an age-structure diagram is top-heavy, with more individuals in the post-reproductive age groups, the population is likely to:
- A Decrease in size
- B Increase in size
- C Remain stable
- D Exhibit a sudden 'baby boom'
Correct answer: Decrease in size
A top-heavy pyramid indicates a declining population. With fewer individuals in the reproductive and pre-reproductive stages, there will be fewer births to replace the aging members of the population.
The time it takes for a population to double in size can be estimated using the 'Rule of 70' if the growth rate is known. This applies to:
- A Logistic growth model
- B Linear growth
- C Negative growth
- D Exponential growth
Correct answer: Exponential growth
The doubling time formula (70 / annual growth rate percentage) assumes a constant per capita growth rate, which is the definition of exponential growth.
Which factor is a common cause of density-dependent regulation?
- A Competition for mates
- B Volcanic eruption
- C A devastating tsunami
- D A late spring frost
Correct answer: Competition for mates
Density-dependent factors have a greater impact as the population density increases. Competition for resources or mates intensifies as more individuals crowd into the same space.
A life table is a summary of:
- A Age-specific survival and reproductive rates
- B The specific dietary preferences of a species
- C The different habitats a species occupies
- D The genetic diversity within a population
Correct answer: Age-specific survival and reproductive rates
Life tables track a cohort (a group of individuals born at the same time) from birth until death. They provide data on age-specific mortality and the number of offspring produced by each age group.
The Allee effect occurs when:
- A Individuals have lower fitness at low densities
- B Population growth slows down at high densities
- C The carrying capacity of an environment increases
- D Predators switch to the most abundant prey
Correct answer: Individuals have lower fitness at low densities
While most models focus on overcrowding, the Allee effect describes species that struggle when their numbers are too low. This might happen because they can't find mates or because group behaviors (like schooling or pack hunting) become ineffective.