Nitrogen (select all that apply):

a. is not a nutrient.

b. is transferred into the living world in nature through the actions of plants.

c. is transferred into the living world in nature through the actions of bacteria.

d. has been manufactured by humans since the early twentieth century.

e. exists in such low concentrations in some coastal waters that “dead zones” are the result.

Tundra and desert are in some ways more fragile biomes than are grasslands or forests. Why should this be so?

There is a simple food chain in an eastern Oregon desert grassland: Mice are consumed by several species of snakes, which are consumed by hawks. The hawk is a __________ and occupies the __________ trophic level in this ecosystem.

a. tertiary consumer; fourth

b. secondary consumer; fourth

c. tertiary consumer; third

d. secondary consumer; third

e. primary consumer; third

A dung beetle (can you guess what it eats?) is an example of a:

a. detritivore.

b. omnivore.

c. carnivore.

d. herbivore.

e. producer.

Concentrations of heat-trapping “greenhouse” gases such as carbon dioxide are measured in:

a. kilograms.

b. tons.

c. parts per billion.

d. parts per million.

e. millions of molecules.

The greenhouse effect is caused by:

a. incoming long-wave radiation that is trapped as short-wave radiation by the atmosphere.

b. short-wavelength light that is reradiated as long-wave radiation and is trapped by certain gases.

c. heat that is stored as short-wave radiation by rough surfaces of the Earth and then re-radiated as long- wavelength light.

d. cold air masses that mix with the warm gases and produce warm atmospheric gases.

e. reactions in the stratosphere between these greenhouses gases and ozone, producing long-wave heat.

You walk in on the middle of a nature program on television and see aerial shots of huge expanses of one or two types of coniferous trees. The type of biome you are looking at probably is:

a. chaparral.

b. taiga.

c. tundra.

d. savanna.

e. temperate forest.

Donna is measuring rainfall over a large elevation gradient in the Cascade Mountains of Oregon. As she walks up the west side, she notices that rainfall increases and that when she reaches the top and walks down the east side, it is much drier. This is because:

a. dry air from the equator flows east at this latitude, dropping moisture on the west side.

b. wet air from the tropical equator flows east at this latitude, dropping moisture on the west, and then becomes dry by the time it reaches the eastern side.

c. air is flowing from the west and drops moisture as it rises and cools, then absorbs moisture from the land as it descends and warms.

d. warm air from 30° latitudes picks up moisture as it travels to 60° north, then drops this moisture as it cools.

e. the rain-shadow effect means that cool, moist air drops rainfall as it warms with a rise in elevation.

A lake affected by high levels of artificial eutrophication will have:

a. high nutrient levels, large phytoplankton populations, and low oxygen levels at depth.

b. high level, nutrients, low phytoplankton levels, and high oxygen levels in surface waters.

c. low nutrient levels, large phytoplankton populations, and low oxygen levels at depth.

d. low nutrient levels, low phytoplankton populations, and high oxygen levels at depth.

e. low nutrient levels, large zooplankton populations, and low phytoplankton levels.

An ecosystem includes a ________ of organisms and the _______ with which they interact.