BLY 122- Chapter 46

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

- both are liberated into the environment when organisms decompose - both are required to make the primary biological molecules - microorganisms have important roles in the cycling of each

Which of the answer choices are reservoirs of carbon? Select all that apply.

- soil - oceans - organisms - the atmosphere

Researchers are measuring Earth's atmospheric CO2 levels, gathering data on CO2 levels in northern and then southern hemispheres. What do you expect that they 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 equations is the chemical reaction for cellular respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O

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

CaCO3

Which of these organisms is considered a primary consumer?

a grasshopper

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

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

atmospheric CO2 levels were higher during the Cambrian Period than today

A team of scientists studying a material have determined that 12C, 13C, and 14C occur in the material in a ratio of 1000:10:1. How did they 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

Which group in a food web is responsible for returning inorganic compounds back to the environment?

decomposers

Hans Suess's work (and subsequent studies carried out by other researchers) determined that the amount of 13C in Earth's atmosphere has _____ and the amount of 14C in the atmosphere has _____.

decreased; also decreased

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

denitrifying bacteria

A community of organisms and the physical environment it occupies are known together as a(n):

ecosystem

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

T/F: 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

T/F: Glacial ice core data can provide scientists with information about atmospheric CO2 levels for the last 500 million years of Earth's history.

false

T/F: If all of the tertiary consumers were removed from an environment, the associated food web, and thus the carbon cycle, would collapse.

false

T/F: Most phosphorus on the planet is found in living organisms.

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

Nutrient cycling through ecosystems can be depicted using a(n):

food web

A _____ depicts the flow of carbon through an ecosystem, whereas a _____ depicts the transfer of energy.

food web; trophic pyramid

To some extent, Earth's surface reflects solar radiation (in the form of heat), which is subsequently absorbed by certain _____ gases in the atmosphere, such as methane and CO2.

greenhouse

Which of the statements is true regarding chemical weathering?

it contributes to the accumulation of CaCO3 in oceans

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

Organisms in an ecosystem are linked to their physical environment through the cycling of _____ and the transfer of _____.

nutrients; energy

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

The equation 6CO2 + 6H2O → C6H12O6 + 6O2 represents the process of:

photosynthesis

Cyanobacteria, milkweed plants, and oak trees are all considered:

primary producers

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

primary producers

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

rates of oxygen consumption are lower than rates of photosynthesis

The rate of respiration _____ throughout the year.

remains more or less constant

The equation C6H12O6 + 6O2 → 6CO2 + 6H2O represents the process of:

respiration

Decomposers are vital components of a food web because they:

return carbon (as CO2) to the atmosphere

Photosynthesis and respiration both play a major role in the _____ carbon cycle and can affect atmospheric CO2 levels on a seasonal or annual basis.

short-term

How can scientists distinguish among different sources of CO2 in the atmosphere?

the amount of different carbon isotopes in the CO2 differs based on the source.

Which of the processes is responsible for the change scientists observed in atmospheric concentrations of 12C, 13C, and 14C over the last 200 years?

the burning of fossil fuels

Which of the statements is true regarding subduction?

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

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

trophic pyramid

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)

T/F: Primary consumers obtain carbon, nitrogen, and phosphorus through ingestion of primary producers.

true

T/F: The evolution of biodiversity on the planet can be linked to patterns in the carbon cycle over time.

true

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

yearly; century

What can Antarctic ice core samples tell us about atmospheric CO2 levels? Select all that apply.

- CO2 ice core data confirm CO2 measurements taken directly from the atmosphere - ice cores can help scientist estimate atmospheric CO2 levels from hundreds of thousands of years ago

Which of the statements is true regarding the carbon cycle?

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

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

- the fact that O2 is also cycled during the carbon cycle - the fact that photosynthesis released O2 as a product - the evolution of cyanobacteria - the fact that there is a slight "de-coupling" between photosynthesis and respiration

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

Approximately _____ of the energy and biomass available at one trophic level is passed to the next.

10%

Because energy transfer is not 100% efficient across trophic levels, an average of about _____ of energy and biomass available at one trophic level is available at the next.

10%

T/F: Photosynthesis and respiration were the main causes of fluctuations in atmospheric CO2 levels over the last 500 million years.

false

T/F: Scientists can gain information about ancient atmospheric CO2 levels through ice core data. CO2 in ice cores is primarily the result of sediments being trapped in glaciers, which scientists can subsequently assess for different carbon isotopes 13C, 12C, and 14C.

false

T/F: The diverse array of photosynthetic plants and microbes is the result of different sources of CO2 and has little to do with environmental conditions.

false

The movement of Earth's crust, plate tectonics, contributes to the long-term carbon cycle through all of the answer choices except:

photosynthesis

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

T/F: 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