Population Ecology

All living things within an ecosystem are interdependent. A change in the size of one population affects all other organisms within the ecosystem. One well known predator/prey relationship is between ladybugs (predator) and aphids (prey). What happens to the population of ladybugs if there is an increase in aphids?

• The ladybug population will decrease.

• The ladybug population will increase.

• The ladybug population will remain the same.

• The ladybug population will remain the same because ladybugs can only eat so may aphids.

Answer explanation

The ladybug population will increase is correct. Predator numbers will respond to the increased food supply by increasing.

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This tree contains examples of several food chains. Birds live in the tree and eat insects they find within the branches. Insects eat parts of the tree (like bark and leaves). The transfer of energy moves from the tree to insects and then to birds.

Where does the tree get its energy from? Where does the energy for these food chains begin?

• as wind energy

• as solar energy

• as kinetic energy

• as synthetic energy

Answer explanation

All plants rely on the sun. All animals depend on plants. Some animals eat plants for food, and some animals consume other animals that eat plants for food.

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A tapeworm is an organism that lives inside the intestines of larger animals, including man, and absorbs nutrients from its host. This type of symbiotic relationship is called

• commensalism

• mutualism

• parasitism

• predation

Answer explanation

This kind of symbiotic relationship is called parasitism.. A parasite lives in or on another organism called a host. The parasite benefits from the host by draining nutrients and the host is harmed by the interaction with the parasite.

Which factor would INCREASE the carrying capacity for white-tailed deer in an Eastern temperate forest ecosystem?

• The re-introduction of the Eastern cougar into North Carolina.

• A large migration of the closely related mule deer, into the East.

• The construction of new roads and increased traffic through woodland areas.

• The re-introduction of the American chestnut tree, which produces many seeds, and used to live in North Carolina.

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A scientist studied animals that live in a forest over a period of a year. His observations are shown in the table. At the end of the year the scientist found that the fox population had increased to 40.

Which animal will MOST LIKELY be affected by this increase?

• Bears

• Rabbits

• Sparrows

• Robins

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Look at the food chain illustrated here. Frogs react very quickly to changes in their habitat. What would happen to the food chain if the frogs began to die off?

• The number of insects and grasses will get larger.

• The numbers of living things at each level will get smaller.

• The insect numbers would get larger; the grass numbers would get smaller.

• The number of snakes will get much larger; the insect number will get smaller.

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^{The population of mice in a local forest ecosystem has recently died out due to disease. In the past, these mice made up a large part of the diet of the forest fox. What is the best prediction about what will happen to the foxes?}

• The drop in the mouse population will lead to a drop in the fox population.

• The drop in the mouse population will lead to no change in the fox population.

• The drop in the mouse population will lead to an increase in the fox population.

• The increase in the mouse population will lead to an increase in the fox population.

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Elk herds in Yellowstone National Park are herbivores that eat on the available vegetation. Which factor is important to ensure the stability of this ecosystem?

• The introduction of another herbivorous species to increase competition.

• The introduction of more elk from other parks to increase the herd population.

• The predators, such as grey wolves, to keep the elk population from growing too large.

• Ensuring that only vegetation that is part of the elk’s diet is allowed to grow in the park.

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The Arctic fox has to compete with other predators for its food sources. The main food sources for the Arctic fox are rabbits and other small rodents. What would happen if competition for food in the Arctic increased and it was difficult for the Arctic fox to find its prey?

• The Arctic fox population will decline.

• The Arctic fox population will increase.

• The Arctic fox population will remain the same.

• The Arctic fox population will increase and then decrease only slightly.

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The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment. What factors would increase a carrying capacity for a population?

I. habitat loss

II. increase in food sources

III. access to clean water

IV. increase in competition

V. increase in diseases

• II and III

• III and IV

• I, II, and V

• II, IV, and V

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