11. Is an individual with light skin color living at high latitude at risk of having low serum folate levels due to UV exposure? Why or why not? 12. Is an individual with dark skin color living at low latitude at risk of having vitamin D deficiency due to lack of UV exposure? Why or why not?

Carbon cycles from the atmosphere into plants and living things. For example, carbon is a pollutant in the atmosphere as carbon dioxide.

But it’s also the most important building block for all living things including glucose.

Over millions of years, carbon can get re-purposed into hydrocarbons. This is the long-term carbon cycle.

So, carbon takes up various forms: glucose in plants, carbon dioxide in the air and hydrocarbons like coal.

1. Photosynthesis

Plants pull in carbon dioxide out of the air through photosynthesis. Even though carbon dioxide makes up less than 1% of the atmosphere, it plays a major role for living things.

With CO2 and H2O in the atmosphere, photosynthesis produces sugars like glucose. This is the plant material that plants synthesize on their own.

If you have the right conditions, this process can repeat for centuries. Not only does photosynthesis pulls carbon dioxide out of the atmosphere, but it’s fuels all living things as a source of energy.

2. Decomposition

By mostly using sunlight, water and carbon dioxide, plants can grow. In turn, animals consume food for energy using oxygen and giving off carbon dioxide. Alternatively, they die, decay and decompose repeating for millions of years.

Decomposition is the process of breaking down plants. Over vast periods of time, layers of sediment build on each other. Because of the pressure and heat from within the Earth’s crust, this generates fossil fuels. Much of this happened during the Carboniferous Era.

For example, coal, oil and natural gas (methane) are some of the common fossil fuels. Over the long-term, the decomposition of dead matter generates these fossil fuel products.

Anaerobic decomposition involves bacteria breaking down organic matter such as glucose into carbon diaoxide and methane  The nutrient cycle recycles inorganic and organic material in soil through the process of decomposition. Then, it goes back again through the same process again.

3. Respiration

You and I are both made of carbon. We consume plants. But we also breathe in the air, which has carbon in the form of carbon dioxide.

Animals rely on plants for food, energy and oxygen. Our cells require oxygen to break down the food we consume through cellular respiration.

Once consumed, carbon dioxide is released into the atmosphere because of cell respiration. In turn, this CO2 produced from respiring cells can be used in photosynthesis again.

In other words, the plants use solar energy to break apart that same carbon dioxide in the air. Through photosynthesis, it uses that same carbon for plant material in turn releasing oxygen again.

4. Combustion

Gas Combustion

Our cars use carbon in the form of fossil fuels. And carbon is also a pollutant as carbon dioxide

We extracting fossil fuels, combustion involves burning them to produce energy. But a by-product of combustion is that it releases carbon dioxide back into the atmosphere. And too much CO2 increases the greenhouse effect.

And as we deplete our oil reserves adding CO2 into the air daily, this affects the carbon cycle with an imbalance of oxygen and carbon. Carbon dioxide is one of the greenhouse gases contributing to climate change.

But there is a limit for how much fossil fuels we can extract. Over millions of years, phytoplankton resting on the ocean surface photosynthesizes and takes in CO2.

Using sunlight, it creates a molecule called glucose (C6H12O6) and sinks to bottom of the ocean. Humans discovered these fossil fuels beneath the ocean and started to drill the ancient plankton which became oil.