Carbon Cycle - Guided Notes

​The Carbon Cycle

By Clint Primoff

​Carbon is the basic building block of all

organic materials.

The cycle has two interconnected parts:

• Rapid carbon exchange among

  living organisms.

• Long-term cycling through

  geologic processes.
  
  

Multiple Choice

Based on the fact that carbon is the basic building block of all organic materials, which of the following would contain the highest density of organic carbon?

• A granite mountain

• The Pacific Ocean

• The Amazon rainforest

• Earth's atmosphere

​The Carbon Cycle

By Clint Primoff

​The largest reservoirs of carbon are

inorganic minerals in crustal rocks, the oceans, and the atmosphere.

​Slow Carbon Cycle

After millions of years of burial and compression, decomposed plants and algae can form fossil fuels such as coal, oil, and natural gas.

Atmospheric CO2​ dissolves in the ocean and reacts with water to form carbonate ions.

These ions combine with calcium to form

calcium carbonate (CaCO3​), a major component of marine organism shells.

When these organisms die, their shells form sediments which can become

limestone, the largest carbon reservoir on Earth.

Ocean sediments are returned to the surface through

volcanic activity or geologic uplifting.

Multiple Choice

If scientists were looking for the most massive, long-term storage of carbon, which of the Earth's spheres would hold the largest reservoir?

• The atmosphere (air)

• The biosphere (all living things)

• The hydrosphere (oceans and water)

• The lithosphere (crustal rocks)

Multiple Choice

The text explains that fossil fuels are formed from decomposed organisms under pressure for millions of years. What can you infer from this?

• Fossil fuels are a renewable resource on a human timescale.

• The carbon in fossil fuels was once part of living organisms in the ancient, rapid carbon cycle.

• Burning fossil fuels has no effect on the modern carbon cycle.

• All decomposed organisms will eventually become fossil fuels.

​Fast Carbon Cycle

Photosynthesis by plants, algae, and some bacteria converts
CO2​ into glucose.

*Aerobic cellular respiration by organisms breaks down organic molecules and releases CO2​ back into the atmosphere.

Decomposition of dead organisms by bacteria and fungi also releasesCO2​ or methane (CH4​).

Photosynthesis removes CO2​ from the atmosphere, while respiration returns it.

Multiple Choice

A plant absorbs carbon dioxide from the atmosphere, and then a rabbit eats the plant. This chain of events is best described as part of which section of the carbon cycle?

• Long-term cycling through geologic processes

• Rapid carbon exchange among living organisms

• The formation of inorganic minerals in rocks

• The release of carbon from volcanic activity

• Humans release

  CO2​ into the atmosphere by burning fossil fuels and through land use change like deforestation.

• Burning fossil fuels moves carbon from long-term reserves into the active carbon cycle.

• High levels of atmospheric CO2​ cause warming that results in climate change.

​Human Alteration of the Carbon Cycle

Multiple Choice

Atmospheric CO₂ dissolving in the ocean is a key step in the slow carbon cycle. What would be a logical consequence if the amount of CO₂ in the atmosphere significantly increased?

• The ocean would become less acidic as it absorbs the extra CO₂.

• The process of forming carbonate ions in the ocean would likely accelerate.

• Marine organisms would find it easier to build shells.

• The ocean would release more CO₂ into the atmosphere to maintain balance.

Multiple Choice

Calcium carbonate (CaCO₃) is essential for shell-building marine organisms. What is the most likely direct impact on these organisms if there is a significant decrease in available carbonate ions in the ocean?

• The organisms would adapt and use a different mineral to build their shells.

• The organisms' shells would likely become thinner, weaker, or grow more slowly.

• The organisms would move to land to find more calcium.

• There would be no impact, as the organisms can create their own carbonate.