Ecology 2020

The heath hen was a wild bird that was once common from New England to Virginia. By 1900, habitat changes and hunting by humans had reduced the heath hen population size to about 100 birds. The species became extinct in 1932.

Which of the following would have been most effective in preventing the decline in the population size of wild heath hens?

• vaccinating baby heath hens against human diseases

• establishing protected natural areas where heath hens lived

• introducing new bird species to put selective pressure on heath hens

• attaching metal bands to the legs of heath hens to identify them as a protected species

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 growth of plants in many ecosystems is limited by the supply of nitrogen. Which of the following groups of organisms plays the largest role in moving nitrogen between the atmosphere and plants?

• bacteria

• earthworms

• insects

• protists

Which of the following statements describes one way that energy is transferred in a food web?

• Plants provide energy to consumers.

• Energy is cycled between producers.

• Producers store energy made by animals.

• Consumers obtain energy directly from sunlight.

A population of mosquito larvae is living in a large pond. Mosquito-fish are a type of fish that eat mosquito larvae.

Which of the following describes a direct effect on the population of mosquito larvae when mosquito-fish are introduced to the pond?

• births decrease

• deaths increase

• emigration increases

• immigration decreases

The green sea turtle is an endangered species. The graph above shows the estimated number of green sea turtle nests on a beach in Costa Rica between 1970 and 2003.

Based on the information in the graph, which of the following is the most likely way humans affected the green sea turtle population during this time?

• Humans passed laws preventing the collection of green sea turtles.

• Humans collected more green sea turtle eggs for scientists to study.

• Humans passed laws protecting animals that eat green sea turtle eggs.

• Humans built more hotels on the beach where green sea turtles build nests.

The diagram above shows an energy pyramid for an aquatic ecosystem.

Which of the following statements best explains why the energy pyramid is narrowest at the top?

• The organisms at the top of the pyramid are the most efficient feeders.

• The organisms at the top of the pyramid have the largest population sizes.

• The organisms at the top of the pyramid need only a small amount of energy for their metabolism.

• The organisms at the top of the pyramid receive only a small fraction of the energy that originally enters the system.

In 1937, two male and six female ring-necked pheasants were introduced to an island off the coast of Washington state. The pheasants mainly ate wheat.

The only known predators on the island were house cats, hawks, and owls. After five years, the pheasant population on the island had increased to 1,325 individuals. The population size then remained stable.

Which of the following most likely explains why the pheasant population size remained stable after five years?

• The hawks learned to hunt only owls.

• A limited amount of wheat grew on the island.

• All the house cats that lived on the island died.

• The original male and female ring-necked pheasants died.

A partial food web is shown above.

Which of the following describes the relationship between the earthworms and the beetles in the food web?

• The earthworms and the beetles both compete for fungi.

• The earthworms and the beetles both compete for robins and moles.

• The earthworms help the beetles survive, and the beetles do not harm the earthworms.

• The earthworms help the beetles survive, and the beetles help the earthworms survive.

The New England cottontail is the only rabbit native to New England. Current populations are small and isolated because of habitat loss. Scientists are concerned about the possible extinction of the New England cottontail.

Which of the following statements explains why having small and isolated populations puts these rabbits at risk for extinction?

• Diet requirements of the rabbits are changed, making the emigration rate increase.

• Male-to-female ratios in the populations are changed, making the birth rate fall to zero.

• Immigration is increased, making it harder for the rabbits to successfully compete for resources.

• Genetic variation is decreased, making the populations less able to adapt to environmental changes.