Ecology: Chapter 2.2Ecology: Chapter 2.2

The Carbon CycleThe Carbon Cycle

Framing QuestionsFraming Questions

What is photosynthesis? What is the equation What is photosynthesis? What is the equation for it? for it?

What is cellular respiration? What is the What is cellular respiration? What is the equation for it?equation for it?

What role does carbon play in these two What role does carbon play in these two processes?processes?

Explain the carbon cycleExplain the carbon cycle What happened during the Carboniferous What happened during the Carboniferous

Period? How does this affect us today?Period? How does this affect us today?

PhotosynthesisPhotosynthesis

Recall that we discussed plants capturing Recall that we discussed plants capturing energy from the sun and passing it along food energy from the sun and passing it along food chains. How do they do this?chains. How do they do this?

Plants use the sun’s light to make carbohydrates Plants use the sun’s light to make carbohydrates in the process of in the process of photosynthesisphotosynthesis

6CO6CO2 2 + 6H+ 6H220 + energy -> C0 + energy -> C66HH1212OO66 + 6O + 6O66

CarbonCarbon water water Sun Sun carbohydrates oxygen carbohydrates oxygen

dioxidedioxide

Photosynthesis, Continued…Photosynthesis, Continued… So why are we talking about photosynthesis if this lesson is So why are we talking about photosynthesis if this lesson is

about the carbon cycle?about the carbon cycle? Photosynthesis is Photosynthesis is one of the stagesone of the stages in the carbon cycle. in the carbon cycle.

Plants “capture” carbon from the atmosphere in the form of Plants “capture” carbon from the atmosphere in the form of carbon dioxide and combine it with water to make carbon dioxide and combine it with water to make carbohydratescarbohydrates

Plants then use these carbs to make other carbon Plants then use these carbs to make other carbon compounds such as fats and proteins (food/energy to be compounds such as fats and proteins (food/energy to be used and passed on)used and passed on)

Consumers eat the plants (or eat organisms that have eaten Consumers eat the plants (or eat organisms that have eaten plants), gain the carbon compounds, and break them down plants), gain the carbon compounds, and break them down to build tissue… carbon is an important part of the to build tissue… carbon is an important part of the structure of all living things!structure of all living things!

The Story So Far…The Story So Far…

So, if plants use carbon to create food energy, and So, if plants use carbon to create food energy, and consumers use the carbon food energy from plants to consumers use the carbon food energy from plants to live, then why isn’t this gas eventually all used up?live, then why isn’t this gas eventually all used up? Only 0.03% of the Earth’s atmosphere is carbon dioxideOnly 0.03% of the Earth’s atmosphere is carbon dioxide

There must be another process that returns this carbon There must be another process that returns this carbon to the atmosphere to complete the cycle.to the atmosphere to complete the cycle.

Well, we said that the energy consumers gain is Well, we said that the energy consumers gain is partially used up to do things like grow, reproduce partially used up to do things like grow, reproduce and move… and during these processes, the and move… and during these processes, the organism’s cells are respirating.organism’s cells are respirating.

Cellular RespirationCellular Respiration

What does that mean?What does that mean? Cells need oxygen and carbohydrates to work, and Cells need oxygen and carbohydrates to work, and

when they get these, they use them to do the tasks when they get these, they use them to do the tasks required for daily life.required for daily life.

As they do, they break down the oxygen and As they do, they break down the oxygen and carbohydrates and give off waste that looks like this:carbohydrates and give off waste that looks like this:

6O6O6 6 + C+ C66HH1212OO6 6 -> 6CO-> 6CO2 2 + 6H+ 6H220 + energy 0 + energy oxygen carbohydrates carbonoxygen carbohydrates carbon water Sun water Sun

dioxidedioxide Look familiar?Look familiar?

Let’s Compare:Let’s Compare:

PhotosynthesisPhotosynthesis::

6CO6CO2 2 + 6H+ 6H220 + energy -> C0 + energy -> C66HH1212OO66 + 6O + 6O66 carbon watercarbon water Sun Sun carbohydrates oxygen carbohydrates oxygen

dioxidedioxide

Cellular RespirationCellular Respiration::

6O6O6 6 + C+ C66HH1212OO6 6 -> 6CO-> 6CO2 2 + 6H+ 6H220 + energy 0 + energy oxygen carbohydrates carbonoxygen carbohydrates carbon water water

dioxide dioxide

These make up the two halves of the carbon cycle!These make up the two halves of the carbon cycle!

The Carbon Cycle in a NutshellThe Carbon Cycle in a NutshellIn the carbon cycle, carbon and oxygen move back and forth In the carbon cycle, carbon and oxygen move back and forth

between living things (biotic) and their environment (abiotic)between living things (biotic) and their environment (abiotic)1.1. PhotosynthesisPhotosynthesis captures carbon from the air and uses it to captures carbon from the air and uses it to

make food energy for animalsmake food energy for animals2.2. Animals eat plants and use the food energy to live. Their cells Animals eat plants and use the food energy to live. Their cells

respirate as they carry out their life processesrespirate as they carry out their life processes3.3. Cellular respirationCellular respiration breaks apart carbohydrate molecules in breaks apart carbohydrate molecules in

cells and releases the carboncells and releases the carbon4.4. This carbon is returned to surrounding air or water and can be This carbon is returned to surrounding air or water and can be

used again for used again for photosynthesisphotosynthesis5.5. Decomposers break down dead organisms and waste from Decomposers break down dead organisms and waste from

animals and absorb the carbon from the cells or waste. They animals and absorb the carbon from the cells or waste. They return it back to the environment through return it back to the environment through cellular respirationcellular respiration

Remember: only producers carry out photosynthesis, but all organisms, Remember: only producers carry out photosynthesis, but all organisms, including producers, carry out cellular respiration… it is necessary to live!including producers, carry out cellular respiration… it is necessary to live!

The Carbon Cycle The Carbon Cycle in Aquatic Systemsin Aquatic Systems

The worlds oceans and lakes contain up to 50 times The worlds oceans and lakes contain up to 50 times the amount of carbon than the atmospherethe amount of carbon than the atmosphere

Carbon dissolves on the surface of water to form Carbon dissolves on the surface of water to form carbonic acid, which is used by water plants for carbonic acid, which is used by water plants for photosynthesisphotosynthesis

Shells of underwater creatures use carbon (calcium Shells of underwater creatures use carbon (calcium carbonate – carbon, calcium and oxygen) carbonate – carbon, calcium and oxygen) When these organisms die, their shells fall to the ocean When these organisms die, their shells fall to the ocean

floor, and harden into sedimentary rock.floor, and harden into sedimentary rock. Carbon is eventually released back into the systemCarbon is eventually released back into the system

Disrupting the Carbon CycleDisrupting the Carbon Cycle Oh, these cycles are just so delicate, aren’t they?!Oh, these cycles are just so delicate, aren’t they?! Usually, the amount of COUsually, the amount of CO22 produced through produced through

cellular respiration equals the amount absorbed for cellular respiration equals the amount absorbed for photosynthesisphotosynthesis Thus, the amount of carbon dioxide in the atmosphere has Thus, the amount of carbon dioxide in the atmosphere has

remained fairly constantremained fairly constant When too much carbon is released into the When too much carbon is released into the

atmosphere, or too little is available, the balance atmosphere, or too little is available, the balance changes.changes.

What do you think happens?What do you think happens?

The Carboniferous PeriodThe Carboniferous Period 300 million years ago, swamps became filled with 300 million years ago, swamps became filled with

decaying plant matterdecaying plant matter This was buried under thick sediment and with the This was buried under thick sediment and with the

absence of Oabsence of O2 2 , decomposers could not break down , decomposers could not break down the materialthe material This caused large amounts of carbon to be locked in the This caused large amounts of carbon to be locked in the

groundground Over millions of years, this plant matter and carbon Over millions of years, this plant matter and carbon

compressed, and converted to coal and oil (fossil compressed, and converted to coal and oil (fossil fuels)fuels)

Now that we’re using all of these fossil fuels today, Now that we’re using all of these fossil fuels today, what do you think could happen to the cycle?what do you think could happen to the cycle?