FREE Ecology Population Growth Models Questions and Answers

Question 1

A population of yeast is introduced to a new, nutrient-rich environment in a laboratory setting. Initially, the population grows rapidly, doubling in size at regular intervals. Which of the following statements BEST describes this initial phase of growth?

Accepted Answer

The population is exhibiting exponential growth, characterized by a constant per capita growth rate.

Answer

In an environment with abundant resources and no limiting factors, populations tend to exhibit exponential growth. This model is characterized by a J-shaped curve where the per capita growth rate (r) remains constant, and the total population growth accelerates as the number of individuals increases.

Question 2

Which of the following scenarios is an example of a density-independent limiting factor affecting a population?

Accepted Answer

A severe, late-spring frost kills a large percentage of oak tree seedlings in a forest.

Answer

Density-independent factors affect a population regardless of its density. A frost is an abiotic, weather-related event that will impact the seedlings' survival whether there are many or few in the area. The other options (disease, competition, predation) are all density-dependent factors, as their effects become more pronounced as the population density increases.

Question 3

The logistic growth model is described by the equation dN/dt = rN((K-N)/K). What does the term (K-N)/K represent?

Accepted Answer

The fraction of the carrying capacity that is still available for population growth.

Answer

In the logistic growth equation, 'K' is the carrying capacity and 'N' is the current population size. The term (K-N) represents how many more individuals the environment can support. Dividing this by K, (K-N)/K, gives the fraction of the carrying capacity that has not yet been utilized, which acts as a moderating force on the exponential growth term (rN).

Question 4

An organism that is long-lived, produces few, well-cared-for offspring, and lives in a stable environment is best described as:

Accepted Answer

A K-strategist

Answer

K-strategists are adapted to stable environments where the population tends to be near the carrying capacity (K). Their life history traits include long life, slow development, late reproduction, large body size, and significant parental investment in a few offspring. Elephants and humans are classic examples. In contrast, r-strategists thrive in unstable environments and produce many offspring with little parental care.

Question 5

A population of harbor seals experiences growth that initially is rapid, then slows, and finally fluctuates around a certain level. This pattern, which produces an S-shaped curve when plotted, is known as:

Accepted Answer

Logistic growth

Answer

The S-shaped (or sigmoidal) curve is the hallmark of the logistic growth model. This model describes how a population's growth rate decreases as it approaches the carrying capacity (K) of its environment due to limited resources. Initially, when the population is small and resources are plentiful, growth is nearly exponential, but it must slow down as environmental resistance increases.

Ecology Practice Test

Ecology Practice Test

FREE Ecology Population Growth Models Questions and Answers