Carbon Cycle MCQs and Answers

Are you looking for Carbon Cycle MCQs and Answers for medical entrance examinations? If yes, these are some most important multiple choice questions and answers on NCERT Class-12 Biology, Chapter-14 (Ecosystem).

Here we composed these Carbon Cycle MCQs and Answers after reading the chapter on Ecosystem from the NCERT book on Class 12 Biology. The questions are topics-wise and the students can relate the questions easily to the most important topics of this chapter.

Carbon Cycle MCQs and Answers

1. What percent of dry weight does carbon constitute in the living organisms?

a) 55 percent

b) 49 percent

c) 20 percent

d) 90 percent

Answer: b


2. Which is the most abundant constituent found in living organisms?

a) Water

b) Oxygen

c) Ammonia

d) Hydrogen bicarbonate

Answer: a


3. Out of the total quantity of global carbon, what percent of carbon is found dissolved in oceans?

a) 50 %

b) 71 %

c) 90 %

d) 25 %

Answer: b


4. Which reservoir regulates the amount of carbon dioxide in the atmosphere?

a) Gaseous reservoir

b) Sedimentary reservoir

c) Atmospheric reservoir

d) Oceanic reservoir

Answer: d


5. What percent of total global carbon does the atmosphere contain?

a) 5 %

b) 50 %

c) 1%

d) 20 %

Answer: c


6. Whose reservoir does fossil fuel represent?

a) Oxygen

b) Carbon

c) Helium

d) Argon

Answer: b


7. From which stages does the carbon cycling occur?

a) Dead organisms → Living organisms → Oceans

b) Atmosphere → Living organisms → Dead organisms

c) Oceans → Atmosphere → Dead organisms

d) Atmosphere → Oceans → Living organisms → Dead organisms

Answer: d


8. What amount of carbon is fixed in the biosphere through photosynthesis annually?

a) 1013 kg

b) 20 × 1020 kg

c) 4 × 1013 kg

d) 80 × 1035 kg

Answer: c


9. By which process does the carbon return to the atmosphere as CO2?

a) Decayed organisms

b) Calcareous sediments

c) Photosynthesis

d) Respiration

Answer: d


10. Which of the following organism contributes to the CO2 pool by the processing of waste materials and dead organic matter?

a) Carnivores

b) Herbivores

c) Decomposers

d) Producers

Answer: c


11. Which human activities have significantly influenced the carbon cycle?

a) Afforestation

b) Deforestation only

c) Burning of fossil fuel only

d) Both deforestation and burning of fossil fuel

Answer: d


12. In which form does the carbon dioxide precipitate after dissolving in water?

a) Calcium oxide

b) Carbon mono-oxide

c) Calcium carbonate

d) Calcium phosphate

Answer: c


13. What product does the plants from by photosynthesis using carbon dioxide?

a) Lipids

b) Carbohydrates

c) Proteins

d) Salts

Answer: b


14. Which one of the following plants use as a source for carbon dioxide?

a) Carbonate rocks

b) Calcium rocks

c) Fossils

d) Atmospheric CO2

Answer: d


15. For releasing CO2 in the atmosphere, how are fossil fuels exploited?

a) Mined and burned

b) Fragmented and leached

c) Leached and burned

d) Mined and fragmented

Answer: a


The carbon cycle is the process by which carbon is cycled through the Earth’s atmosphere, oceans, and land. The cycle is important for regulating the Earth’s climate and for supporting life on Earth. Here are some frequently asked questions about the carbon cycle:

FAQs on Carbon Cycle

1. What is the carbon cycle?

Answer: The carbon cycle is the process by which carbon is cycled through the Earth’s atmosphere, oceans, and land. The cycle is important for regulating the Earth’s climate and for supporting life on Earth.

2. How does the carbon cycle work?

Answer: The carbon cycle works by exchanging carbon between the atmosphere, oceans, and land. The process begins when plants take in carbon dioxide from the atmosphere and use it to photosynthesize. This carbon is then either released back into the atmosphere or stored in the land or ocean. When animals eat plants, they release carbon dioxide back into the atmosphere.

3. What are the benefits of the carbon cycle?

Answer: The carbon cycle is important for regulating the Earth’s climate and for supporting life on Earth. The cycle helps to remove carbon dioxide from the atmosphere, which helps to cool the Earth. The cycle also helps to store carbon in the land and ocean, which can be used by plants and animals.

4. What are the consequences of disrupting the carbon cycle?

Answer: Disrupting the carbon cycle can have serious consequences for the Earth’s climate and for life on Earth. If carbon dioxide is not removed from the atmosphere, it can trap heat and cause the Earth to warm. If carbon is not stored in the land or ocean, it can be released into the atmosphere and cause the Earth to warm.

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