Community Interactions and Population Dynamics

Scientists have observed that different species of bats hunt insects at different times of night. Some of these bat species hunt insects high above lakes, and others hunt insects among the trees.

How does hunting at different times of night and at different locations most likely benefit the different bat species?

• It prevents the bat species from breeding with each other.

• It reduces competition among the bat species for food sources.

• It protects the bat species from different types of flying predators.

• It decreases the diversity of the insect populations bat species prey on.

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The graph below shows the changes in the population size of a mammal species introduced onto an isolated island in 1957. Which of the following conclusions is best supported by the data?

• Every year, more individuals were born than died.

• A predator of this mammal was removed from the island in 1990.

• The population decreases were the result of low immigration rates.

• In the 1980s, the mammal’s population size stayed around its carrying capacity.

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A small population colonized an isolated island. Over time, the size of the population increased to its carrying capacity, as represented in the graph below.

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

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Tiger beetles chase small spiders, which they catch in their strong jaws and then eat. What is the ecological relationship between tiger beetles and spiders?

• Competition

• Mutualism

• Parasite-Host

• Predator-Prey

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The graph below 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.

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The graph shows the estimated number of orca whales off the coast of Washington State over a 20-year period.

Which of the following best explains the orca population changes between 1996 and 2002?

• The number of orcas born was less than the number of orcas that died.

• The number of orcas emigrating (leaving) was higher than the number of orcas immigrating (coming in).

• The total number of orca births and immigrants was more than the total number of orca deaths and emigrants.

• The total number of orca births and immigrants was more than the total number of orca immigrants and emigrants.

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The graph below shows changes in the size of a mammal population in the early 1900s.

Which of the following explanations is the most likely reason for the dramatic population change between 1915 and 1925?

• a decrease in the birth rate of the mammal population

• an increase in the death rate of the mammal population

• a large decrease in the number of the mammal’s predators

• a large increase in snowfall for several months in the mammal’s habitat

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The graph shows the change in the size of a mammal population.

Which of the following statements could explain the change in population size in region X?

• Birth rate is greater than death rate.

• Emigration rate is greater than birth rate.

• Death rate is greater than immigration rate.

• Emigration rate is greater than immigration rate.

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Within a prey population, which of the following is most immediately affected by the arrival of a new predator?

• death rate

• evolution rate

• immigration rate

• maturation rate

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At the end of 2009, there were 240 individuals in a particular coyote population. In 2010, scientists monitoring the population recorded 85 births and 68 deaths.

A student used this data to calculate the size of the coyote population at the end of 2010. The student’s calculation is shown.

The actual number of coyotes at the end of 2010 was not 257; it was 294.

Which of the following statements explains the difference between the calculated and actual population sizes?

• The calculation does not include coyote immigration and emigration.

• The calculation does not consider the life expectancy of the average coyote.

• The calculation does not consider the average number of coyote pups in a litter.

• The calculation does not include changes in the number of breeding adult coyotes.

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