BETAThis platform is under active development; bugs, missing features, and risk of data loss are present. Thank you for your support!

Loading…

Earth's spheres and the carbon cycle

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

Practice questions

Free preview — 8 of 58 questions. Sign up to see them all.

1.Which of the following is the largest active pool of carbon near the Earth's surface?
Easy
- AAtmosphere
- BTerrestrial biosphere
- COcean
- DSediments
2.Methane produces a larger greenhouse effect per volume than carbon dioxide.
Easy
True or false?
3.Which process removes carbon dioxide from the atmosphere and converts it into organic carbon?
Medium
- ARespiration
- BPhotosynthesis
- CCombustion
- DDecomposition
4.Match each sphere with its primary component.
Medium
- Geosphere
- Hydrosphere
- Atmosphere
- Biosphere
- Rocks and minerals
- Water
- Air
- Living organisms
5.Place the following steps in the correct order to describe the fast carbon cycle: (a) Carbon dioxide is released by respiration, (b) Carbon dioxide is absorbed by photosynthesis, (c) Carbon is incorporated into organic compounds, (d) Carbon is returned to the atmosphere.
Hard
- Carbon dioxide is absorbed by photosynthesis
- Carbon is incorporated into organic compounds
- Carbon is returned to the atmosphere via respiration
- Carbon dioxide is released by respiration
6.Which of the following are carbon sinks? (Select all that apply)
Hard
- AAtmosphere
- BOceans
- CFossil fuel deposits
- DForests
- EVolcanoes
7.The slow carbon cycle involves processes that take millions of years. Which of the following is an example of a slow carbon cycle process?
Hard
- APhotosynthesis
- BRespiration
- CFormation of fossil fuels
- DDecomposition of leaf litter
8.Carbon dioxide contributes more to the global greenhouse effect than methane.
Medium
True or false?

More questions

9.Match each Earth sphere with its primary carbon reservoir.
Medium
- Atmosphere
- Hydrosphere
- Geosphere
- Biosphere
- Carbon dioxide and methane
- Dissolved inorganic carbon and marine biota
- Rocks and fossil fuels
- Organic carbon in organisms and soils
10.Place the following steps in the correct order to describe how carbon moves from the atmosphere into the ocean and then into rocks (slow carbon cycle):
Medium
- Carbon dioxide dissolves in rainwater forming carbonic acid
- Carbonic acid reacts with rocks, releasing calcium ions
- Calcium carbonate precipitates and accumulates on the ocean floor
- Carbon is buried in sediments and eventually forms limestone
11.Which of the following are examples of fast carbon cycle processes? (Select all that apply)
Hard
- APhotosynthesis
- BBurning of fossil fuels
- CRespiration
- DFormation of limestone
- EDecomposition of organic matter
12.The ocean contains the largest active pool of carbon near the Earth's surface.
Easy
True or false?
13.Arrange the following carbon reservoirs in order from the one that stores the most carbon to the one that stores the least (based on typical estimates):
Hard
- Atmosphere
- Terrestrial biosphere (plants and soils)
- Ocean
- Sediments (including fossil fuels)
14.Which of the following are human activities that have increased atmospheric carbon dioxide? (Select all that apply)
Medium
- ABurning fossil fuels
- BDeforestation
- CPlanting trees
- DManufacturing concrete
- EUsing solar panels
15.Photosynthesis removes carbon dioxide from the atmosphere and converts it into organic carbon.
Easy
True or false?
16.A student measures the pH of rainwater in a region with high atmospheric CO₂. Which of the following best explains the pH value being lower than 5.6?
Medium
- ACarbon dioxide dissolves in water to form carbonic acid, which lowers pH.
- BCarbon dioxide reacts with water to form calcium carbonate, which is acidic.
- CCarbon dioxide absorbs heat and warms the water, causing it to become acidic.
- DCarbon dioxide is a base, so it neutralises the rainwater.
17.Which of the following best describes the role of the ocean in the carbon cycle?
Medium
- AIt is the largest active carbon pool near Earth's surface, exchanging CO₂ with the atmosphere.
- BIt stores carbon only as dissolved CO₂ and does not participate in biological processes.
- CIt absorbs CO₂ only through physical dissolution and not through biological uptake.
- DIt releases more CO₂ than it absorbs, acting as a net carbon source.
18.Which of the following are examples of slow carbon cycle processes? (Select all that apply)
Medium
- AFormation of fossil fuels over millions of years
- BPhotosynthesis by a tree
- CWeathering of silicate rocks that removes CO₂ from the atmosphere
- DRespiration of a rabbit
- EVolcanic eruption releasing CO₂ from the mantle
19.A student investigates the effect of temperature on the rate of carbon dioxide uptake by aquatic plants. They place a plant in water with a pH indicator that turns yellow in acidic conditions and blue in alkaline conditions. They measure the time for the indicator to turn blue at different temperatures. Which of the following is a valid conclusion from the data?
Hard
- AHigher temperature increases the rate of photosynthesis, so CO₂ uptake is faster and the indicator turns blue sooner.
- BHigher temperature decreases the solubility of CO₂, so less CO₂ dissolves and the indicator turns blue more slowly.
- CTemperature has no effect on the rate of photosynthesis because enzymes are denatured at all temperatures.
- DHigher temperature causes the plant to respire more, releasing CO₂ and making the indicator stay yellow longer.
20.The terrestrial biosphere stores more carbon in soils than in living plants.
Medium
True or false?
21.A student wants to measure the rate of photosynthesis in an aquatic plant by counting oxygen bubbles. Which of the following would be the most appropriate method to vary the carbon dioxide concentration available to the plant?
Medium
- AAdd different amounts of sodium hydrogencarbonate (NaHCO₃) to the water
- BChange the temperature of the water
- CUse lamps of different wattages
- DChange the species of aquatic plant
22.In an experiment to investigate the effect of temperature on the rate of carbon dioxide uptake by aquatic plants, a student places a plant in water containing a pH indicator that changes colour as CO₂ concentration changes. The initial colour is red. After 30 minutes in the dark, the indicator turns yellow. Which of the following best explains the colour change?
Hard
- AThe plant respired, releasing CO₂ which formed carbonic acid, lowering the pH.
- BThe plant photosynthesised, using up CO₂ and raising the pH.
- CThe water absorbed CO₂ from the air, increasing acidity.
- DThe indicator reacted with oxygen produced by the plant.
23.In an experiment to measure the rate of decomposition of organic matter in soil, a student places soil samples in sealed jars and measures the CO₂ concentration inside the jar over several days. The increase in CO₂ is solely due to microbial respiration.
Medium
True or false?
24.A student plans to investigate the effect of temperature on the rate of decomposition of leaf litter. Which of the following should the student keep constant to ensure a fair test? (Select all that apply)
Hard
- AMass of leaf litter
- BType of leaf litter
- CMoisture content of the leaf litter
- DTemperature of the environment
- EVolume of the container
25.Arrange the following steps in the correct order to measure the rate of decomposition of organic matter in soil by trapping carbon dioxide.
Medium
- Add soda lime to a container to absorb CO₂
- Weigh the container with soda lime
- Place the container with soil in a sealed jar
- After several days, reweigh the container with soda lime
- Calculate the mass of CO₂ produced from the increase in mass
26.Match each experimental method with the carbon cycle process it measures.
Medium
- Counting oxygen bubbles from an aquatic plant
- Measuring CO₂ increase in a sealed jar with soil
- Using a pH indicator in water with an aquatic plant
- Rate of photosynthesis
- Rate of decomposition
- Rate of carbon dioxide uptake or release
27.A student sets up an experiment to compare the rate of carbon dioxide uptake by two different species of plant. They place each plant in a sealed chamber with a CO₂ sensor and measure the decrease in CO₂ concentration over 10 minutes. The results show that Plant A decreased CO₂ concentration by 50 ppm, while Plant B decreased it by 30 ppm. The student concludes that Plant A has a higher rate of photosynthesis. Which of the following is the most important additional variable the student should have controlled?
Medium
- AThe mass or leaf area of each plant
- BThe volume of the chamber
- CThe initial CO₂ concentration
- DThe time of day
28.Which of the following Earth spheres includes all living organisms?
Easy
- AAtmosphere
- BBiosphere
- CHydrosphere
- DGeosphere
29.The largest active pool of carbon near the Earth's surface is found in the:
Easy
- AAtmosphere
- BTerrestrial biosphere
- COcean
- DSediments
30.Carbon dioxide is the only form of carbon in the Earth's atmosphere.
Easy
True or false?
31.Match each Earth sphere with its primary carbon reservoir component.
Medium
- Atmosphere
- Hydrosphere
- Geosphere
- Biosphere
- Carbon dioxide and methane
- Dissolved inorganic carbon
- Carbonate rocks and fossil fuels
- Organic carbon in living and dead organisms
32.Place the following steps in the correct order to describe the fast carbon cycle: (a) Carbon dioxide is released by respiration, (b) Carbon dioxide is absorbed by plants during photosynthesis, (c) Carbon is stored in plant biomass, (d) Animals eat plants and use carbon for growth.
Medium
- (a)
- (b)
- (c)
- (d)
33.Which of the following is an example of a slow carbon cycle process?
Medium
- APhotosynthesis
- BRespiration
- CFormation of limestone from marine shells
- DDecomposition of leaf litter
34.Methane produces a larger greenhouse effect per volume than carbon dioxide, but carbon dioxide contributes more to the global greenhouse effect overall.
Medium
True or false?
35.Match each Earth sphere to its primary component.
Easy
- Geosphere
- Hydrosphere
- Atmosphere
- Biosphere
- Rocks and minerals
- Water in oceans, lakes, and rivers
- Air and gases
- All living organisms
36.Place the following steps in the correct order to describe how carbon moves from the atmosphere into the ocean and then into rocks (slow carbon cycle).
Medium
- Carbon dioxide dissolves in ocean water
- Carbon dioxide reacts with water to form carbonic acid
- Carbonic acid reacts with calcium ions to form calcium carbonate
- Calcium carbonate accumulates on the ocean floor and becomes limestone
37.Which of the following processes is part of the slow carbon cycle?
Medium
- APhotosynthesis
- BRespiration
- CFormation of limestone from marine sediments
- DDecomposition of leaf litter
38.Place the following steps in the correct order to describe the fast carbon cycle: (a) Carbon dioxide is released by respiration, (b) Carbon dioxide is absorbed by plants during photosynthesis, (c) Animals eat plants and obtain carbon, (d) Organic carbon is returned to the atmosphere through decomposition.
Hard
- Carbon dioxide is absorbed by plants during photosynthesis
- Animals eat plants and obtain carbon
- Carbon dioxide is released by respiration
- Organic carbon is returned to the atmosphere through decomposition
39.Complete the sentence.
Easy
The four major spheres of Earth are the geosphere, hydrosphere, atmosphere, and ____.
40.State one human activity that has increased the amount of carbon dioxide in the atmosphere.
Medium
41.Approximately how many gigatons of carbon are stored in soils?
Medium
42.Complete the sentence about carbon dioxide in the atmosphere.
Easy
In 2024, the global average atmospheric carbon dioxide reached a record high of ____ parts per million.
43.If the pre-industrial atmospheric CO₂ concentration was 280 ppm and the 2024 concentration is 422.7 ppm, calculate the percentage increase. Give your answer to one decimal place.
Hard
44.The pre-industrial atmospheric CO₂ concentration was 280 ppm. In 2024, it reached 422.7 ppm. Calculate the percentage increase. Give your answer to one decimal place.
Hard
45.Name one human activity that has increased the amount of carbon dioxide in the atmosphere.
Easy
46.Complete the sentence about the greenhouse effect.
Easy
Methane produces a larger greenhouse effect per ____ than carbon dioxide, but carbon dioxide contributes more to the global greenhouse effect because it is more ____.
47.The terrestrial biosphere stores about 500 gigatons of carbon in living plants and about 1500 gigatons in soils. What is the total amount of carbon stored in the terrestrial biosphere, in gigatons?
Medium
48.Complete the sentence using the words provided: (autotrophs, heterotrophs, carbon dioxide, organic carbon)
Easy
In the carbon cycle, ____ convert ____ into ____ through photosynthesis.
49.Complete the sentence about the ocean and carbon dioxide.
Medium
When carbon dioxide dissolves in seawater, it reacts to form ____, which lowers the ocean's ____.
50.The pre-industrial atmospheric CO₂ concentration was 280 ppm. In 2024 it reached 422.7 ppm. Calculate the percentage increase. Give your answer to one decimal place.
Hard
51.Explain why the ocean is considered a carbon sink and describe one consequence of increased atmospheric carbon dioxide on ocean chemistry.
Hard
52.Describe the difference between the fast and slow carbon cycles, giving an example of each.
Medium
53.Describe a method a student could use to investigate the effect of light intensity on the rate of carbon dioxide uptake by a terrestrial plant. Include details of the equipment and how the rate would be measured.
Medium
54.Approximately how many gigatons of carbon are stored in soils?
Medium
- A1650 gigatons
- B1500 gigatons
- C1350 gigatons
- D1800 gigatons
55.If the pre-industrial atmospheric CO₂ concentration was 280 ppm and the 2024 concentration is 422.7 ppm, calculate the percentage increase. Give your answer to one decimal place.
Hard
- A56 %
- B51 %
- C46 %
- D61 %
56.The pre-industrial atmospheric CO₂ concentration was 280 ppm. In 2024, it reached 422.7 ppm. Calculate the percentage increase. Give your answer to one decimal place.
Hard
- A61 %
- B46 %
- C56 %
- D51 %
57.The terrestrial biosphere stores about 500 gigatons of carbon in living plants and about 1500 gigatons in soils. What is the total amount of carbon stored in the terrestrial biosphere, in gigatons?
Medium
- A1800 Gt
- B2400 Gt
- C2200 Gt
- D2000 Gt
58.The pre-industrial atmospheric CO₂ concentration was 280 ppm. In 2024 it reached 422.7 ppm. Calculate the percentage increase. Give your answer to one decimal place.
Hard
- A51 %
- B56 %
- C61 %
- D46 %

Flashcards

What are Earth's four main spheres?

Geosphere, hydrosphere, atmosphere, and biosphere.

Define the carbon cycle.

The carbon cycle is the biogeochemical cycle in which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere.

What is the difference between the fast and slow carbon cycles?

The fast (biological) cycle completes within years, moving carbon between atmosphere and biosphere. The slow (geological) cycle takes millions of years, moving carbon through the Earth's crust.

Name the major carbon reservoirs (pools).

Atmosphere, terrestrial biosphere, ocean (including dissolved inorganic carbon and marine biota), sediments (including fossil fuels), and Earth's interior (mantle and crust).

Which reservoir contains the largest active pool of carbon near Earth's surface?

The ocean.

What are the two main forms of carbon in the atmosphere?

Carbon dioxide (CO₂) and methane (CH₄).

How is carbon dioxide removed from the atmosphere?

Primarily through photosynthesis, and also by dissolving directly into water bodies or precipitation.

What happens when carbon dioxide dissolves in water?

It reacts with water to form carbonic acid, which contributes to ocean acidity.

How have human activities increased atmospheric carbon?

By burning fossil fuels, manufacturing concrete, and modifying ecosystems, increasing CO₂ by nearly 50% since pre-industrial times.

What is the current (2024) global average atmospheric CO₂ concentration?

422.7 parts per million (ppm).

What is the terrestrial biosphere?

It includes all land-living organisms (alive and dead) and carbon stored in soils.

How much carbon is stored above ground in plants and in soils?

About 500 gigatons above ground; soil holds approximately 1,500 gigatons.

What are autotrophs and heterotrophs in the carbon cycle?

Autotrophs (e.g., plants) convert CO₂ into organic carbon via photosynthesis. Heterotrophs obtain carbon by consuming other organisms.

What is a carbon sink?

A carbon sink is a reservoir that stores carbon, removing it from the atmosphere (e.g., forests, oceans).

How does the ocean absorb carbon dioxide?

CO₂ dissolves directly from the atmosphere into the ocean, where it forms carbonic acid and can be used by marine organisms.

What is the greenhouse effect?

The trapping of heat in the atmosphere by gases like CO₂ and methane, which absorb and retain heat.

Which greenhouse gas contributes more to global warming per volume?

Methane produces a larger greenhouse effect per volume than CO₂, but it is less abundant and shorter-lived.

What is the carbonate–silicate cycle?

A geological cycle where CO₂ is absorbed into soil via weathering, forming carbonate rocks, eventually returning CO₂ through volcanic activity.

How might the carbon cycle end in the far future?

As the Sun ages, increased weathering could trap CO₂ in crust; later, when oceans evaporate, plate tectonics stop, ending volcanic CO₂ release.

What is the role of photosynthesis in the carbon cycle?

Photosynthesis removes CO₂ from the atmosphere and converts it into organic carbon in plants.

What is the role of respiration in the carbon cycle?

Respiration by organisms releases CO₂ back into the atmosphere as organic carbon is broken down.

How does burning fossil fuels affect the carbon cycle?

It releases ancient organic carbon as CO₂, increasing atmospheric CO₂ and disrupting the natural balance.

What is ocean acidification?

The decrease in ocean pH caused by increased CO₂ dissolving in seawater, forming carbonic acid.

Unlock all 58 questions, flashcards & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

Coming soon