Populations

Billy observes that some trees in a forest are clumped together, some are uniformly separated, and some appear to be spaced randomly.  What is he describing?

• population density

• population distribution

• population growth.

• population outline

Dr. Faerts concludes that a population of ducks has reached the carrying capacity of the prairie where it lives. The birth rate and death rate of the duck population are equal to each other. What can be concluded about the rates of immigration and emigration?

• The rates of immigration and emigration are equal to each other

• The rate of either immigration or emigration is zero

• The rate of immigration equals the birth rate

• The rate of emigration equals the death rate

A hurricane blows across Florida not only disrupting the Florida Man population but many others. The storm flattens trees, and it drowns or washes away a large number of plants and animals. As a result of the storm, the carrying capacity of the state is temporarily reduced for many of the island species.

How is the storm classified as a limiting factor?

• The storm is a density-independent limiting factor, because population size and density do not alter the storm’s effect.

• The storm is a density-independent limiting factor, because its effect depends on the size and density of a population.

• The storm is a density-dependent limiting factor, because its effect depends on the size and density of a population.

• The storm is a density-dependent limiting factor, because its effect depends on the strengths of its wind and rainfall.

Stilka is a type of grass. In the wild, orungoos eat stilka almost exclusively. For this reason, the availability of stilka is a significant limiting factor on the orunga population.

Which statement describes how orungoos might become exctinct?

•             The stilka population decreases so low that other limiting factors begin to affect the orungoo population.

• The stilka population drops so low that the carry capacity for orgunoos is reduced to 0.

• The populations of stilka and organoos follow a cyclical pattern of increasing and decreasing, until one of them goes extinct.

• The populations of stilka and organoos both follow a pattern of exponential growth, and then both become extinct.

Which of these events is most likely to occur during Stage II of the demographic transition?

• The population decreases slightly, especially in the younger age ranges.

• The population decreases slightly, especially in the older age ranges.

• The population increases slightly, due mainly to the increased rate that babies are born.

• The population increases significantly, due mainly to a decrease in death rate.

Which of the following pairs of populations is most likely to increase and decrease in a similar pattern to the wolves and moose?

• Willow trees, which are the primary diet of the moose and the moose itself

• Very old wolves in young wolf pups

• Moose and the beneficial bacteria that live in the digestive tracts of moose

• Male wolves and female wolves

Lake Tefillin is a large freshwater lake that is popular for recreation. One year, the managers of the lake introduce a population of rainbow trout to the lake. The graph shows the growth of the population over several years. Which best describes the growth pattern of the rainbow trout?

• Exponential growth, because the lake provides unlimited resources to the population

• Logistic growth, because the effect of limiting factors increases with the population size.

• Exponential growth, because limiting factors are always affecting the population.

• Logistic growth, because the lake provides unlimited resources until the population reaches carrying capacity.

In the eighteenth century, the population of sea otters decreased significantly along the California coast. Scientists cite the hunting of sea otters by humans as the cause of this decrease.

Today, the population of invasive pandafish is growing rapidly in the sea of dreams. However, scientists argue that human hunting or harvesting of pandafish will not affect the population.

Which comparison of sea otters and pandafish is most useful for explaining the potential impact of human hunting on their populations?

• Pandafish have a much shorter average lifespan.

• Pandafish have a much higher death rate.

• Pandafish have a much higher birthrate.

• Pandafish have a much narrower geographic range.

A tropical ecosystem is home to populations of a variety of animals, including deer, jaguars, rodents, toucans, and vultures. Which change to the ecosystem is most likely to decrease the sizes of every tropical population by the same percentage, regardless of its initial size or distribution?

• the introduction of a new herbivore species to the ecosystem

• the removal of the jaguar, the largest animals of the ecosystem

• the conversion of half of the ecosystem into farms and ranches

• a gradual increase of average temperature by 1.5°C over the next century.

Nutria are rodents and native to South America. They are an invasive species in the southeastern United States, where they have no natural predators. Nutria thrive in freshwater habitats and estuaries, where they eat a wide variety of vegetation. An adult nutria may eat as much as 2 kilograms of food a day.

Which additional information would be most useful to an ecologist to evaluate the damage to a wetlands ecosystem due to nutria?  Select three answer choices.

• the average body weight of a nutria

• the population density of nutria in the wetlands

• the birth rate and death rate of nutria in the wetlands

• the immigration and emigration rates of nutria in the wetlands