Lesson video

This lesson is called "The Carbon Cycle," and is from the unit Carbon Cycle and Climate Change.

Hi there, My name's Mrs. McCready, and I'm here to guide you through today's lesson.

So, thank you very much for joining me today.

In our lesson today, we're going to describe the carbon cycle and explain the effect of changes to parts of the cycle.

Now, we're gonna come across a number of keywords in our lesson today, and they're listed up here on the screen for you now.

You may wish to pause the video to make a note of them, but I will introduce them to you as we come across them.

So, in our lesson today, whilst we're looking at the carbon cycle, we're going to break it down into three separate sections.

First of all, we're going to look at transferring carbon dioxide out of the atmosphere, then we're gonna look at how carbon is transferred without a gas before we consider how we transfer carbon dioxide back into the atmosphere.

So, are you ready to go? I certainly am, let's get started.

So, what is the carbon cycle? Well, the carbon cycle is a process, quite a complex one at that which describes how carbon moves between the atmosphere, living organisms, and the Earth's surface and layers and the oceans, and continues to move around and between these different parts on a continuous rolling basis.

Now, the carbon cycle is what is known as a closed system.

That means that no carbon is being removed from the system, no carbon is being added into it.

So, the quantity of carbon in the whole of the Earth system is remaining constant, just where it is located is changing over time as carbon moves through the carbon cycle.

Now, most of the carbon in the atmosphere is stored in the form of carbon dioxide, CO2, and it is this that is used with water and sunlight by plants in the process of photosynthesis to create biomass, to create mass for plants, to help plants build their body.

So, the equation for photosynthesis is carbon dioxide and water with the energy from sunlight radiation being used to produce glucose and oxygen, and you can see the word and the balance symbol equation there on the screen.

So, this is the process of photosynthesis and is one of the ways that carbon dioxide is removed from the atmosphere and stored in plant matter because the carbon is used to form glucose, and then glucose can be made into lots of other substances which are used to build a plant's body such as cellulose and lignin and a huge range of proteins for instance.

Now, only about half of all of the photosynthesis that takes place across the globe is carried out by plants found on land, trees, shrubbery, a flowering plants, that sort of thing.

The other half of all of the photosynthesis that takes place on Earth is carried out by a remarkable range of organisms called phytoplankton, and by some types of bacteria, all of which live in the oceans.

Now, all of these organisms are microscopic.

They are far too small to be seen with a naked eye, but they are there and they are essential for carrying out photosynthesis within the oceans and for removing carbon dioxide outta the atmosphere by this process of photosynthesis.

So, which is the correct equation for photosynthesis? A, B, or C? I'll give you five seconds to decide.

Okay, so you should have chosen A, carbon dioxide plus water makes glucose and oxygen.

Well done if you got the correct answer there.

So, we've seen how photosynthesis removes carbon dioxide out of the atmosphere, but carbon dioxide can also be removed from the atmosphere by the oceans themselves, not through the phytoplankton and the bacteria which are living there and photosynthesizing, but because carbon dioxide can dissolve in the water of the oceans.

So, carbon dioxide can dissolve in the oceans, also oxygen can dissolve in the oceans in the water.

Now, fish need oxygen dissolved in the ocean water in order to live.

They use it for respiration just like we do.

And carbon dioxide is also necessary within the oceans for a number of different reasons, including photosynthesis by phytoplankton and bacteria, and also to make other compounds which we'll look at in a moment.

So, carbon dioxide transfers outta the atmosphere into living things through the process of photosynthesis, both on land and within the oceans, and it also transfers out into the oceans by dissolving in the water.

So, these are two ways that carbon dioxide can be removed from the atmosphere.

Now, carbon dioxide concentrations are increasing in the atmosphere due to human activity.

So, the things that we are doing on Earth are causing carbon dioxide to be released in great quantities into the atmosphere, in particular when we burn fossil fuels and release the carbon as carbon dioxide that way.

And we'll look at that process in a little bit more detail in a moment.

Now, if there is more carbon dioxide in the atmosphere, which there certainly is now, then more carbon dioxide will be able to be dissolved in the oceans.

And so more carbon dioxide will find its way into the oceans, and it's estimated that about 30% of the extra carbon dioxide that human activity has released into the atmosphere will be dissolved in the oceans.

So, how is carbon dioxide transferred out of the atmosphere? By combustion, by dissolving, by photosynthesis or by respiration? I'll give you five seconds to decide.

Okay, so you should have said that carbon dioxide is transferred out of the atmosphere by dissolving in the oceans and by photosynthesis by plants, phytoplankton and bacteria.

Well done if you got both of those.

So, what I'd like you to do is to summarise this first part of the lesson about transferring carbon dioxide outta the atmosphere by firstly completing the word equation for photosynthesis, and then by stating two examples of organisms that photosynthesize, then finally stating two ways that carbon dioxide is transferred out of the atmosphere.

So, pause a video and come back to me when you are ready.

Okay, let's check our work.

So, firstly, I asked you to complete the photosynthesis word equation.

So, you should have added carbon dioxide into the first gap because carbon dioxide and water makes glucose and oxygen.

Then I asked you to state two examples of organisms that photosynthesize, and you could have listed plants, phytoplankton and some types of bacteria in the oceans.

And then I asked you to state two ways that carbon dioxide is transferred outta the atmosphere, and you should have said by photosynthesis and by dissolving in the oceans.

So, check over your work, make sure you've got all of those parts correct, amend anything that is wrong and well done indeed.

Okay, let's move on now to look at how carbon is transferred without a gas.

So, carbon is transferred in many different ways through the carbon cycle and it can be transferred in a non-gaseous form.

And this is how it is passed from one living organism to another by eating.

So, the grass has taken carbon dioxide as a gas into its system by the process of photosynthesis.

So, that's a gas transfer.

But from that point onwards through the food chain, carbon is being transferred in a non-gas process.

So, the rabbit is eating the grass, and that transfers the carbon from the grass into the rabbit in a non-gas process.

And then the fox eating the rabbit transfers carbon from the rabbit into the fox's body again in a non-gas process.

So, in a food chain, carbon is transferred through the food chain by the process of eating in a non-gas form.

Carbon can also be transferred from living organisms into the soil through animal waste and through decay.

So, when organisms die and decompose, they can transfer carbon into the soil, and animal waste such as faeces can also transfer carbon into the soil.

And both of these processes can happen without carbon being in the form of a gas.

So, it can be carbon is therefore in a form which is bound up in other ways, such as in proteins and carbohydrates within the organisms body.

So, how is carbon transferred from the atmosphere into an animal? Is it by photosynthesis and eating? By photosynthesis, respiration and eating, or by photosynthesis and respiration? I'll give you five seconds to decide.

Okay, so you should have said that carbon is transferred from the atmosphere into an animal by photosynthesis and by eating.

Well done if you spotted that.

We've also seen how carbon dioxide is dissolved into the oceans.

And when that happens, it can form carbonate ions.

It can react with the water to form these carbonate ions.

And this is very important because these ions are used by sea animals to build their shells or their bones.

So, the shells of muscles, for instance, are made by using the carbonate ions created when carbon dioxide dissolves in the ocean and converting it into the shells of the muscle.

Now, when these organisms die, their shells or their bones may settle at the bottom of the ocean, and if over time these parts of their body which get ground down into a powder essentially through just general wear and tear on the ocean, if they become cemented together, they can form sedimentary rock.

Now, sedimentary rock is a great store of carbon on Earth, and in fact, almost all of the carbon on Earth is stored in the form of rocks.

Now, rocks can store carbon for millions or even billions of years because the rock cycle is a very, very slow process.

And because carbon is bound into rock in the form of sedimentary rock, right at the very start of the rock cycle, and then that rock is moved very slowly through the Earth structure and then turned into igneous and metamorphic rock through other processes within the rock cycle, this carbon that was originally stored in the bodies, in the shells and the bones of organisms living in the ocean can be incorporated into sedimentary rock and then passed through the rock cycle in this extremely slow process lasting millions or even billions of years.

And in fact, there are still some rocks present on Earth right back three and a half billion years old or so.

This rock is found very, very deep beneath the Earth's surface, which is why it is stored there for such incredibly long periods of time.

Also, what can happen is that if dead plants and the soft tissue of the dead sea animals are trapped within the sediment at the bottom of the ocean, they don't turn into sedimentary rock.

Instead, what happens to those parts of dead plants and animals is that they are turned into fossil fuels.

Again, this process takes many millions of years to occur.

So, it's not a quick process, but this is how fossil fuels such as coal, oil, and gas are produced.

So, it's not from the bones and the shells of these animals and plants which are trapped at the bottom of the ocean, but it's from the soft tissue that coal, oil and gas are formed.

So, how is carbon transferred from the atmosphere into rocks? Is it by dissolving, shell formation and cementing of sediment? By dissolving bone formation and cementing of sediment? By photosynthesis, shell formation and cementing of sediment, or by photosynthesis, bone formation and cementing of sediment? I'll give you five seconds to decide.

Okay, so you should have said that carbon is transferred from the atmosphere into rocks by dissolving, and the formation of shells and bones that then are cemented to form sediment.

Well done.

So, some carbon can be transferred into animals when they eat, from the soil, from animal waste, and also from dead plants and animals, from the shells and the bones of animals in the ocean, and then from sedimentary rocks, which are formed from the shells and bones of these animals, and also from fossil fuels, which is formed from dead plants and dead animals in the ocean.

So, this is how carbon is transferred into structures on or below the surface of the Earth.

So, how can carbon be transferred in the carbon cycle? From dead animals into rocks? From living animals into soil, or from fossil fuels into dead plants or animals? I'll give you five seconds to decide.

Okay, so you should have chosen from dead animals into rocks and from living animals into soil.

Well done.

So, what I'd like you to do now is to summarise that section of the lesson by reading what Sofia, Laura, Andeep, and Lucas are saying about the carbon cycle.

And firstly, deciding who is correct about the carbon cycle and then by making any changes to those who are incorrect to improve their statements to make them correct.

So, pause the video and come back to me when you are ready.

Okay, let's check our answers.

So, you should have firstly identified that Sofia and Lucas are both correct, because Sofia says that carbon dioxide in the oceans can end up in shells and bones, and Lucas correctly says that carbon from dead sea creatures can end up in fossil fuels.

But how might you correct what Laura and Andeep have incorrectly said? Well, to correct Laura's statement, instead of saying, when animals eat plants, carbon gets broken down, you should say that carbon is transferred to the animal.

And for Andeep, when organisms die, carbon inside them is destroyed, should be corrected to carbon is transferred into the soil.

Remember, we cannot create or destroy the atoms, we can simply transfer them from one place to another.

So, well done if you've made all of those corrections and identified the correct students statements and do make any further amendments to your work if you need to.

Good work, well done.

Okay, let's move on to the last part of our lesson where we're looking at how carbon dioxide is transferred back into the atmosphere.

So, we've seen how carbon dioxide is removed from the atmosphere through photosynthesis and through dissolving.

We've seen how carbon is moved through food chains and transferred from organisms such as plants and animals into the soil and into sedimentary rock and fossil fuels.

So, let's now see how carbon dioxide is released into the atmosphere.

And one of the key ways that this happens, that this occurs is through cellular respiration.

So, cellular respiration is a chemical process.

It happens inside plant and animal cells to provide energy for life processes and is essentially the reverse of photosynthesis because during cellular respiration, glucose and oxygen are used together to form carbon dioxide and water with a release of energy.

So, you can see how if we turn the arrow around the other way, we have photosynthesis, and therefore respiration is a really easy equation to learn because it is photosynthesis in reverse.

Now, carbon dioxide is transferred as part of the process of cellular respiration.

You can see that that the carbon in the glucose is transferred into carbon dioxide and then released into the atmosphere from plants and animals.

So, that is one way of transferring carbon dioxide into the atmosphere.

Another way is through decomposition.

Now, decomposition is when dead plants and animals and other organic wastes such as faeces are broken down into smaller pieces, and there are lots of organisms that act as decomposers, including beetles and worms, plus of course, bacteria and fungi.

Now, decomposition by fungi, and some bacteria breaks down this organic matter enough to release carbon dioxide into the atmosphere.

And in addition to that, decomposers release carbon dioxide through cellular respiration.

So, some decomposers break down large pieces of organic matter like leaves and tissue of organisms of animals into smaller pieces and use that tissue for the process of cellular respiration to provide themselves with food for energy.

So, these are organisms such as worms and beetles, and then other decomposers, the smaller ones such as fungi and bacteria, use some of the dead animal and plant matter for respiration, but also act in the process of decomposition to break down the carbon-based compounds into carbon dioxide and release that also into the atmosphere.

And therefore, both of these processes are releasing carbon back into the atmosphere, both respiration and decomposition.

So, which is the correct equation for respiration? I'll give you five seconds to decide.

Okay, so you should have chosen C, oxygen plus glucose leads to water and carbon dioxide.

Well done if you chose the correct answer.

So, we've seen some natural processes that release carbon back into the atmosphere, but there is also another process which is not natural, and this is called combustion.

So, combustion is burning of fuel in oxygen, and when fuels are burnt in oxygen, a chemical reaction occurs, which releases carbon dioxide back into the atmosphere.

Now, combustion is used to heat our homes and for cooking because many houses use natural gas as a fuel for these processes.

So, if we burn natural gas with oxygen, we release carbon dioxide and water.

So, this is the process of combustion, and you can see that it's very similar to respiration.

And in this case, we're using natural gas methane, CH4, instead of glucose.

So, combustion is transferring carbon from fuels such as natural gas, coal, and oil back into the atmosphere, usually in the form of carbon dioxide.

Now, the combustion of fossil fuels is still widely used to generate much of the electricity that we use in our daily life, and this is produced through power stations.

Combustion of fossil fuels is also used to power many other vehicles, cars, lorries, boats, and planes all use fossil fuels and therefore release carbon dioxide into the atmosphere as part of their process, as part of moving vehicles or providing electricity for our homes and our businesses.

These processes all release carbon dioxide into the atmosphere if they are using fossil fuels as a source of energy.

So, carbon dioxide transfers back into the atmosphere through several processes, cellular respiration from plants and animals, the decomposition of dead organic matter, and the combustion of fossil fuels and plants.

So, if we're burning fossil fuels, coal, oil, and gas, or if we're using biomass, which is plant matter, we are in those processes transferring carbon dioxide back into the atmosphere.

So, how can carbon be transferred into the atmosphere? By photosynthesis in plants? By respiration in plants? By decomposition of organic matter, or by the production of organic waste in animals? I'll give you five seconds to decide.

Okay, so you should have chosen that carbon is transferred back into the atmosphere via respiration in plants and through decomposition of organic matter.

Well done if you got both of those correct.

So, what I'd like you to do to conclude our lesson on the carbon cycle is to match each of the processes to the correct stages of the carbon cycle.

So, spend your time looking carefully at the diagram and matching them up correctly.

Pause the video and come back to me when you are ready.

Okay, let's see if you've matched the correct parts to the correct stages in the diagram.

So, part one is photosynthesis, and stage two is the dissolving of gases.

Stage three is shell and bone formation, and stage four is rock formation.

Stage five is the formation of fossil fuels.

Stage six is animals eating, and seven is the production of organic waste.

Stage eight is respiration from both plants and animals.

And stage nine is combustion.

Stage 10 is decomposition.

Well done if you've got all of those stages correct.

But do please update your work if you have made any mistakes, and well done.

Okay, we've come to the end of our lesson today, and what we've looked at is the carbon cycle in quite a lot of detail.

So, the carbon cycle we've seen outlines how carbon transfers between the atmosphere, living organisms, the Earth's surface layers, and the ocean in a continuous cycle.

Now, we're not creating or destroying carbon, we are simply transferring it from one place to another, and carbon is transferred from carbon dioxide in the atmosphere into plants and oceans by photosynthesis and by dissolving, it is then transferred into living organisms by eating, and also into the soil through waste.

It is also transferred into rock when sediments of shells and bones are cemented together.

And organic matter can be trapped in sedimentary rock and transferred as carbon into fossil fuels such as coal, oil, and gas.

Carbon can then be transferred back into the atmosphere through cellular respiration in plants and animals, through decomposition of organic matter and by the combustion of fossil fuels and plants.

So, thank you very much for joining me today.

I hope you've enjoyed that lesson and learned a lot, and I hope to see you again soon.

Bye.