Population Ecology

A population of mosquito larvae is living in a large pond. Mosquitofish are a type of fish that eat mosquito larvae. Which of the following describes a direct effect on the population of mosquito larvae when mosquitofish are introduced to the pond?

• births decrease

• deaths increase

• emigration increases

• immigration decreases

The cardinal is a type of bird. Which of the following would increase the size of a population of cardinals in a forest?

• an increase in the birth rate of cardinals

• an increase in the death rate of cardinals

• increased emigration of young cardinals from the forest ecosystem

• increased immigration of cardinal predators into the forest ecosystem

The graph shows changes that occurred in the size of a population of animals over a year. Which of the following is best supported by the graph?

• Between month 1 and month 5, the immigration rate was zero.

• Between month 4 and month 6, a predator was introduced into the ecosystem and increased the death rate.

• Between month 5 and month 7, the birth and emigration rates decreased and the death and immigration rates increased.

• Between month 8 and month 12, the birth and immigration rates equaled the death and emigration rates.

A small population colonized an isolated island. Over time, the size of the population increased to its carrying capacity, as represented in the graph. Which of the following conditions will most likely keep the population at its carrying capacity?

• a death rate of zero

• a death rate that is half the birth rate

• a death rate equal to the birth rate

• a death rate that is twice the birth rate

Pheasants are a type of bird. 2 male pheasants and 6 female pheasants were introduced to an island with abundant food and few predators. Within six breeding seasons, the pheasant population increased from 8 birds to 2,000 birds. Over time, however, the growth rate of the population slowed. Which of the following statements describes the most likely reason for this decrease in population growth rate?

• Females built smaller nests, which decreased the birth rate.

• Competition for resources increased, which increased the death rate.

• Large numbers of birds needed mates, which increased the immigration rate.

• Fewer eggs hatched each successive year, which decreased the emigration rate.

Black bears can be found in several areas in Texas and Mexico. The size of one of these bear populations decreased when some individuals from the population moved to another area. Based on this information, what caused a decrease in the size of this bear population?

• emigration

• extinction

• immigration

• natural selection

Which of the following expressions can be used to calculate the change in the size of a population?

• (births + deaths) + (immigrants – emigrants)

• (births – deaths) + (immigrants – emigrants)

• (births – deaths) + (immigrants + emigrants)

• (births + deaths) + (immigrants + emigrants)

In a certain population, the death rate is greater than the birth rate from year 1 to year 2, and the immigration rate equals the emigration rate. Which of the following graphs represents this information?

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Brown tree snakes were accidentally carried to the island of Guam in the cargo bays of military planes after World War II. Brown tree snakes prey upon birds. There are no natural predators of brown tree snakes on Guam. Which of the following most likely happened as a result of the arrival of the brown tree snakes on Guam?

• Forest biodiversity increased.

• Immigration of new species of birds decreased.

• Many bird populations disappeared.

• All reptile species experienced increases in population size.

The graph shows the changes in a wolf population and a moose population over 30 years. Assume that conditions in the habitat remained similar to those in 1990. Based on the data, which of the following changes most likely occurred from 1990 to 2000?

• The wolf population decreased unchecked.

• The moose population increased unchecked.

• The wolf population increased and the moose population decreased.

• The moose population and the wolf population leveled off at their carrying capacities.