Chapter 46 Learning Curve

Which of the answer choices is a reservoir of carbon?

All of these choices are correct: -organisms -the atmosphere -oceans -soil

Which of these factors likely contributed to the accumulation of O2 within Earth's atmosphere?

All of these choices are correct: -the fact that O2 is also cycled during the carbon cycle -the fact that photosynthesis releases O2 as a product -the fact that there is a slight "de-coupling" between photosynthesis and respiration -the evolution of cyanobacteria

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

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

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.

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.

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

NO3-

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.

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.

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

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

chemical weathering

Because the products of photosynthesis are used as the reactants of respiration, photosynthesis and respiration are considered:

complementary.

A researcher is measuring atmospheric CO2 levels on cloudy and sunny days. He notices that on cloudy days, CO2 levels appear slightly higher than on sunny days. This is an example of:

correlation.

In terrestrial ecosystems, nitrogen is returned to the atmosphere by:

denitrifying bacteria

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

In marine ecosystems, phosphorus is added to the ecosystem primarily from:

erosion of rocks on land.

An increased rate of photosynthesis is the most likely explanation as to why atmospheric CO2 levels appear lowest during glacial periods of Earth's history.

false

If researchers never evaluated the amount of 14C in the atmosphere, they could still use 13C levels to demonstrate causation between human activities and increased atmospheric CO2.

false

A _____ takes into account the diverse interactions between primary producers, consumers, and decomposers. It depicts the flow of carbon through an environment as interdependent of primary producers, consumers, and decomposers.

food web

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

Which of these organisms can incorporate atmospheric carbon directly into C6H12O6, thereby playing a major role in a food web?

primary producers

Energy flow through ecosystems can be depicted using a(n):

trophic pyramid.

The long-term and short-term carbon cycles are connected by the fact that some of the carbon contained in C6H12O6 (or other organic molecules) in plants is incorporated into sedimentary rocks or oil; carbon in sedimentary rock and oil is not immediately cycled back to the atmosphere.

true

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

yearly; century