Skip to content

Quiz: Population Ecology

Test your understanding of how populations grow, stabilize, and decline with these review questions.

1. What is the difference between exponential growth and logistic growth?

  1. Exponential growth occurs only in laboratories while logistic growth occurs in nature
  2. Exponential growth is unlimited and produces a J-curve while logistic growth is limited by carrying capacity and produces an S-curve
  3. Exponential growth applies only to K-selected species while logistic growth applies to r-selected species
  4. Exponential growth increases linearly over time while logistic growth increases at a decreasing rate
Show Answer

The correct answer is B. Exponential growth occurs when resources are unlimited, with the population growing faster as it gets larger, producing a J-shaped curve. Logistic growth incorporates carrying capacity (K) as a limit on growth. As the population approaches K, growth slows and eventually stops, producing an S-shaped curve. In nature, exponential growth may occur briefly but is always eventually constrained by limiting factors.

Concept Tested: Exponential Growth

2. Using the Rule of Seventy, approximately how long would it take a population growing at 2% per year to double?

  1. 20 years
  2. 35 years
  3. 70 years
  4. 140 years
Show Answer

The correct answer is B. The Rule of Seventy states that doubling time equals 70 divided by the growth rate percentage. For a 2% growth rate: 70 / 2 = 35 years. This quick calculation reveals how small differences in growth rates lead to dramatically different outcomes over time. A population growing at 1% doubles in 70 years, while one at 3% doubles in just 23 years.

Concept Tested: Rule of Seventy

3. Which survivorship curve type is characteristic of species that produce many offspring with little parental care?

  1. Type I, where most individuals survive to old age
  2. Type II, where mortality is constant across all age groups
  3. Type III, where most individuals die young but survivors live long
  4. Type IV, where mortality peaks during middle age
Show Answer

The correct answer is C. Type III survivorship curves show high mortality early in life, with the curve dropping steeply at the start and then leveling off for the few survivors. This pattern is typical of r-selected species like oysters, fish, and many insects that produce enormous numbers of offspring with little parental investment. The strategy relies on sheer numbers to ensure some offspring survive to adulthood.

Concept Tested: Type III Survivorship

4. What happens during a population overshoot and crash?

  1. The population grows slowly until it reaches carrying capacity and stabilizes permanently
  2. The population exceeds carrying capacity, depletes resources, and then declines rapidly
  3. The population decreases below carrying capacity and then rebounds to a stable level
  4. The population splits into two separate populations that colonize new habitats
Show Answer

The correct answer is B. Overshoot occurs when a population temporarily exceeds the carrying capacity of its environment. The population depletes resources faster than they can regenerate, leading to a population crash -- a rapid, steep decline that often falls well below the original carrying capacity because the environment has been damaged. The reindeer of St. Matthew Island illustrate this: the population exploded to 6,000, then crashed to 42 after overgrazing the island.

Concept Tested: Overshoot

5. How do density-dependent limiting factors differ from density-independent limiting factors?

  1. Density-dependent factors only affect small populations while density-independent factors affect large ones
  2. Density-dependent factors intensify as population density increases while density-independent factors affect populations regardless of size
  3. Density-dependent factors are caused by humans while density-independent factors are natural
  4. Density-dependent factors affect only predators while density-independent factors affect only prey
Show Answer

The correct answer is B. Density-dependent factors such as competition, disease, and predation get worse as population density increases -- more individuals in a smaller area means more competition for food and faster disease spread. Density-independent factors like hurricanes, droughts, and fires affect populations regardless of how many individuals are present. In reality, both types interact to regulate population size.

Concept Tested: Density-Dependent Factors

  1. Why populations immediately stop growing once fertility reaches replacement level
  2. Why populations continue growing for decades even after fertility drops to replacement level
  3. Why birth rates always increase during periods of economic growth
  4. Why immigration always exceeds emigration in developing countries
Show Answer

The correct answer is B. Population momentum explains why populations continue growing even after reaching replacement-level fertility (TFR of 2.1). When a large generation of young people enters reproductive years, even at replacement-level fertility, the sheer number of couples produces more births than deaths in the smaller, older generation. It is like a freight train that takes a long time to stop after the brakes are applied.

Concept Tested: Population Momentum

7. What shape does an age structure diagram take for a country with rapid population growth?

  1. Column shape with roughly equal numbers in each age group
  2. Inverted triangle with more elderly people than young people
  3. Diamond shape with the largest group in middle age
  4. Pyramid shape with a wide base of young people and narrow top
Show Answer

The correct answer is D. A pyramid-shaped age structure diagram with a wide base indicates rapid population growth. The wide base represents a large proportion of young people who will soon enter their reproductive years, driving continued growth. Countries like Nigeria show this pattern. A column shape indicates slow growth, while an inverted triangle indicates a declining population like Japan.

Concept Tested: Age Structure Diagrams

8. Which traits are characteristic of K-selected species?

  1. Many offspring, short lifespan, little parental care, and Type III survivorship
  2. Few offspring, long lifespan, extensive parental care, and Type I survivorship
  3. Moderate offspring, medium lifespan, and Type II survivorship
  4. Rapid maturation, high reproductive rate, and small body size
Show Answer

The correct answer is B. K-selected species prioritize living near the carrying capacity of their environment. They produce few offspring with heavy parental investment, mature slowly, and live long lives. They typically show Type I survivorship curves where most individuals survive to old age. Examples include elephants, whales, eagles, and humans. This strategy contrasts with r-selected species that prioritize rapid reproduction.

Concept Tested: K-Selected Species

9. During which stage of the demographic transition does population growth occur most rapidly?

  1. Stage 1, when both birth and death rates are high
  2. Stage 2, when death rates drop while birth rates remain high
  3. Stage 3, when birth rates begin to decline
  4. Stage 4, when both birth and death rates are low
Show Answer

The correct answer is B. Stage 2 of the demographic transition sees the most rapid population growth. Death rates drop dramatically due to improvements in sanitation, medicine, and food production, while birth rates remain high because cultural norms and economic incentives for large families have not yet changed. The large gap between high birth rates and low death rates drives rapid population growth.

Concept Tested: Demographic Transition

10. Why are clumped distributions the most common pattern in nature?

  1. Organisms are always territorial and defend evenly spaced areas
  2. Random environmental variation forces organisms into unpredictable positions
  3. Resources are often patchy and many species benefit from social grouping
  4. Predators force prey to spread out uniformly across the landscape
Show Answer

The correct answer is C. Clumped distributions are the most common pattern because resources such as food, water, and shelter are often distributed in patches rather than evenly across a landscape. Additionally, many species benefit from social behavior -- herding for protection, cooperative hunting, or communal nesting. Wolf packs cluster near prey, wildflowers cluster near water sources, and schools of fish aggregate for predator defense.

Concept Tested: Population Distribution