Chapter 46

Which of the statements is true regarding the carbon cycle?

*It involves both long- and short-term processes. *It was based on microbes during the early stages of Earth's history. *It cycles both carbon and H2O. *It evolved before plants appeared on Earth.

Which of the statements is true regarding atmospheric CO2 levels during the last 400,000 years?

Atmospheric CO2 levels fluctuate periodically, with the highest levels occurring during interglacial periods.

A researcher is measuring Earth's atmospheric CO2 levels, gathering data on CO2 levels in northern and then southern hemispheres. What do you expect that she will find?

Because atmospheric CO2 measurements represent global amounts, measurements in the Northern Hemisphere and Southern Hemisphere will be approximately the same.

The majority of carbon stored in abiotic reservoirs is in the form of:

CaCO3.

Which of the statements is true regarding chemical weathering?

It contributes to the accumulation of CaCO3 in oceans.

Which of the answer choices is a form of nitrogen that can be utilized by plants?

NO3-

Which of the statements is true regarding subduction?

The carbon it removes is eventually returned to the atmosphere by volcanism.

A botanist is comparing the metabolic pathways for photosynthesis in cyanobacteria and redwood trees. What do you expect that she will find?

These two pathways will actually be quite similar, though subtle differences may exist.

The observation that atmospheric CO2 levels were typically low during glacial periods in Earth's history is an example of:

correlation.

Photosynthesis and respiration affect atmospheric CO2 levels on a _____ timescale, whereas volcanic eruptions affect atmospheric CO2 levels on a _____ timescale.

yearly; century

The carbon and nitrogen cycles are related to one another because:

*microorganisms have important roles in the cycling of each. *both are required to make the primary biological molecules (carbohydrates, fats, proteins, and sugars). *both are liberated into the environment when organisms decompose.

Which of the answer choices is a reservoir of carbon?

*the atmosphere *organisms *oceans *soil

How many kilograms of biomass at the primary producer level would be required to support 20 kilograms of biomass at the tertiary consumer level?

20,000

Imagine that a researcher has discovered a leaf fossil from the Cambrian Period that is 500 million years old. He notices that the leaf had very few stomata compared to present-day leaves. What does this tell the researcher about atmospheric CO2 levels during the Cambrian Period?

Atmospheric CO2 levels were higher during the Cambrian Period than today.

Imagine that scientists have discovered a new planet that is apparently devoid of life but has ice caps located at the poles. These ice caps reveal that the planet's atmospheric O2 levels sharply increased about 1,000,000 years ago but then quickly dropped 50,000 years ago. What could account for these changes in atmospheric O2 levels?

Photosynthetic organisms evolved on the planet 100,000 years ago but went extinct 50,000 years ago.

Recall that during the Paleozoic Era, atmospheric CO2 levels decreased. Why?

Photosynthetic, woody plants first appeared during this period.

Carbon moves through ecosystems on both short- and long-term scales. Which of the statements best describes the movement of carbon through short-term time scales of the food chain?

Primary producers fix atmospheric carbon into compounds that will be oxidized by secondary consumers.

Which of the statements explains how an oxygen-rich atmosphere became possible on Earth?

Rates of oxygen consumption are lower than rates of photosynthesis.

Trout and amoebas are both heterotrophs and can inhabit similar environments, such as a freshwater pond. However, these organisms are very different when it comes to their shape and size. Why?

Trout and amoebas evolved to utilize different sources of C6H12O6 (or other organic compounds).

A scientist studying a material has determined that 12C, 13C, and 14C occur in the material in a ratio of 1000:10:1. How did he most likely differentiate between these forms of carbon?

by the number of neutrons in 12C, 13C, and 14C

Of the processes involved in the long-term carbon cycle, which removes CO2 from the atmosphere?

chemical weathering

The equation CaSiO3 + CO2 → CaCO3 + SiO2 takes into account which of these processes associated with the long-term carbon cycle?

chemical weathering

Examining the relationship between primary producers, primary consumers, and secondary consumers is one way to track the flow of _____ through a system.

energy contained in organic compounds

Which of these relationships best depicts the amount of carbon stored in the atmosphere, sedimentary rocks, living organisms, and soil?

living organisms < the atmosphere < soil < sedimentary rocks

The _____ cycle deals with geological processes and carbon reservoirs, some of which have been built up or take place over a period of millennia. In contrast, the _____ cycle involves biological processes that are carried out on a daily and/or seasonal basis.

long-term carbon; short-term carbon

Which biogeochemical cycle does not include oxidation and reduction reactions that provide energy to microorganisms?

phosphorus

Recall that in the northern hemisphere, atmospheric CO2 levels are highest in early spring and lowest in early fall. What accounts for this seasonal fluctuation in atmospheric CO2 levels?

photosynthesis

Which of the answer choices are not geological processes that drive the long-term carbon cycle?

photosynthesis and respiration

Decomposers are vital components of a food web because they:

return carbon (as CO2) to the atmosphere.

Of the processes involved in the long-term carbon cycle, which introduces CO2 back into the atmosphere?

volcanism