Lesson video

Hello, I'm Mrs. Adcock and welcome to today's lesson on the carbon cycle.

Today we are going to be answering the question, how does carbon move between the different carbon reservoirs, such as the atmosphere, oceans, and land? Today's lesson outcome is I can describe the carbon cycle and explain the effect of changes to parts of the cycle.

Some of the keywords we will be using in today's lesson include carbon cycle, photosynthesis, respiration, combustion, and decomposition.

Here you can see those keywords written in a sentence.

You might like to pause the video now and read through those statements or pause and maybe make some notes that you can refer back to later in the lesson if needed.

Today's lesson on the carbon cycle is split into three main parts.

The first part is looking at removing carbon dioxide from the atmosphere.

Then we're looking at the transfer of carbon within the cycle, and finally, how carbon dioxide is released back into the atmosphere.

Let's get started on removing carbon dioxide from the atmosphere.

Studying the carbon cycle helps us to understand some of the processes that remove and release carbon dioxide into the atmosphere.

In this diagram here, we can see an overview of the carbon cycle.

We are gonna refer back to this image throughout the lesson when we focus on how carbon moves between the different carbon reservoirs within the carbon cycle.

Carbon is present in the atmosphere predominantly as carbon dioxide.

So this carbon present in each molecule of carbon dioxide is one carbon and two oxygen atoms. Photosynthesis is a process where energy from sunlight is used to convert carbon dioxide and water into glucose and oxygen, and the equation for photosynthesis is carbon dioxide and water react together to produce glucose and oxygen.

But today we're just focusing on carbon and we can see that carbon dioxide has been taken from the atmosphere and those carbon atoms are now present in molecules of glucose.

And photosynthesis is carried out by plants and other photosynthetic organisms. Photosynthesis removes carbon dioxide from the atmosphere and produces carbon-containing glucose molecules in photosynthetic organisms. Photosynthesis is carried out by some types of bacteria, as well as plants and algae.

Right, time for a check of understanding.

Carbon is present in the atmosphere predominantly as A, glucose.

And you can see the molecular formula for glucose is C6H12O6.

B, carbon dioxide, which has the molecular formula, CO2, or C, oxygen, which has the molecular formula O2.

Which of these molecules is carbon predominantly present in in the atmosphere? Well done if you chose B.

So carbon dioxide is present in the atmosphere predominantly as carbon dioxide.

Another question.

The process of photosynthesis removes carbon dioxide from the atmosphere.

What is the correct equation for photosynthesis? Is it A, carbon dioxide and water react together to produce glucose and oxygen? B, Carbon dioxide and glucose react together to produce water and oxygen.

Or C, carbon dioxide and oxygen react together to produce glucose plus water.

Now, try to think about during photosynthesis, carbon dioxide is taken from the atmosphere.

Where do those carbon atoms get transferred into? Into which molecule? See if you can remember and then choose your answer.

Well done if you chose A.

The correct equation for photosynthesis is carbon dioxide and water react together to produce glucose and oxygen.

Carbon dioxide is soluble.

Another way that carbon dioxide is removed from the atmosphere is by dissolving in the oceans, and there's an image there showing us the oceans.

And these oceans contain dissolved carbon dioxide.

So carbon dioxide got removed by the process of photosynthesis and it's also being removed by dissolving in the oceans.

To summarise, carbon dioxide is removed from the atmosphere by the process of photosynthesis and as it dissolves in the oceans.

And you can see the two arrows within our carbon cycle, which represent both of those two processes.

How is carbon dioxide removed from the atmosphere? A, photosynthesis, in plants and algae.

B, combustion of fossil fuels.

C, dissolving in the oceans.

So choose any answers that you think are correct.

The correct answers are A and C.

So photosynthesis and dissolving in the oceans are two ways that carbon dioxide is removed from the atmosphere.

Time for our first practise task of today's lesson.

And what you need to do here is for question one, complete the equation for photosynthesis.

Question two, state two examples of organisms that photosynthesize, and question three, state two ways carbon is removed from the atmosphere.

Pause the video now, have a go at those questions, then come back when you're ready to go over the answers.

The answer to question one is carbon dioxide plus water react together to make glucose plus oxygen.

So well done if you were able to fill in carbon dioxide as a reactant and oxygen as the missing product.

State two examples of organisms that photosynthesize.

Hopefully you chose either some types of bacteria, algae or plants.

Question three, state two ways carbon is removed from the atmosphere.

Carbon dioxide is removed from the atmosphere by the process of photosynthesis and by dissolving in the oceans.

Well done if you remembered both of the ways that carbon is removed from the atmosphere.

Time for us to move on to the second part of our lesson on transfer of carbon.

Carbon dioxide that has dissolved in the oceans can then react to form insoluble carbonate compounds, which are used to make shells and bones.

And we can see in the image there that we've got some mussel shells and these will contain calcium carbonate.

Calcium carbonate is also used to make other types of shells such as oyster and clam shells.

When marine organisms die, these shells and bones settle at the bottom of the ocean where over millions of years they form sedimentary rocks.

The carbon dioxide that was once in the atmosphere and then dissolved into the oceans and formed carbonates in the shells has now become locked up in these sedimentary rocks.

Time for a question.

What can happen to carbon dioxide dissolved in the oceans? A, it reacts to form carbonates that are used to make shells.

B, over millions of years, it becomes locked up in sedimentary rocks.

C, it is eaten by marine animals.

So choose any answers that you think are correct.

The correct answers are A and B.

So well done if you chose A and B.

Carbon dioxide dissolved in the oceans can form carbonates that are used to make shells and also over millions of years, it can become locked up in sedimentary rocks.

Marine plants and algae die along with the animals that consumed them.

The dead remains become buried in mud and rock, forming fossil fuels over millions of years.

That carbon that was once in the atmosphere and then dissolved in the oceans has been used by marine plants and algae when they photosynthesize and then other animals ate them and the carbon would've transferred onto those.

When they died, those plants and algae in the animals, eventually over millions of years, may have formed fossil fuels and those carbon atoms have now become locked up in fossil fuels.

And there's an image there showing coal and coal is an example of a fossil fuel that is rich in carbon.

We have briefly just mentioned this, when animals eat plants and animals eat other animals, the carbon is transferred to the animal that has eaten them.

And here is an example to show carbon being transferred along a food chain.

We've got grass and the carbon in the grass came from the grass photosynthesizing.

The carbon dioxide was taken out of the atmosphere as the plant photosynthesized and it was converted into glucose.

And then those carbon atoms would've transferred to the rabbit when the rabbit ate the grass and then they would've transferred from the rabbit to the fox as the fox ate the rabbit.

And finally, carbon is transferred to the soil in the waste from animals and also when organisms die, then the carbon gets transferred to the soil.

We've just looked at lots of ways that carbon moves within the carbon cycle.

So let's just recap.

Carbon in the oceans forms carbonates in shells and bones.

Carbon can become stored in fossil fuels.

Carbon is transferred from plants to the animals that eat them, and dead organisms and waste material transfer carbon to the soil.

Time for another question.

Which of the following are ways carbon is transferred within the carbon cycle? Is it A, the carbon from dead animals may become part of fossil fuels? B, carbon is transferred to plants when animals eat them.

Or C, carbon from dead organisms can be transferred to the soil.

Now, this is a bit of a tricky question, so read those statements carefully and see if you can select any which you think are correct.

The correct answers are A and C.

So carbon is transferred within the carbon cycle when the carbon from dead animals may become part of fossil fuels and the carbon from dead organisms can be transferred to the soil.

Now, well done if you got those correct.

Carbon is not transferred to plants when animals eat them.

Carbon will be transferred to the animal when they eat the plants.

Time for our second practise task of today's lesson.

What you need to do here is firstly identify who has correctly described ways carbon is transferred between different carbon reservoirs.

And then secondly, make changes to improve any incorrect comments.

So pause the video now, read through each of those statements from those four students.

Decide who you think has made a correct statement, and any statements that you think are incorrect, you need to make improvements to.

Pause the video, have a go and then come back when you're ready to go over the answers.

Well done if you chose Sofia and Lucas as the two students who had made correct statements.

Let's just read through those statements.

Sofia said, "Carbon dioxide in the oceans forms carbonates in shells and bones." So that's correct.

Well done, Sofia.

And Lucas said, "Carbon from dead remains can end up in fossil fuels." So another correct comment.

So Lucas was correct.

Laura says, "When animals eat plants, the carbon atoms get broken down".

Now, that's an incorrect comment.

We can just improve that by saying when animals eat plants, the carbon atoms are passed onto the animal.

They don't get broken down, they get passed from the plant to the animal that eats them.

And Andeep says, "When organisms die, the carbon atoms inside them are destroyed." This is incorrect because the carbon atoms are not destroyed.

When organisms die, the carbon atoms are transferred to the soil.

Well done if you made changes to Laura and Andeep's comments to make them into correct statements.

In the lesson so far, we have looked at ways that carbon dioxide has been removed from the atmosphere.

We have just looked at the way that carbon is transferred in other ways in the cycle.

And now we're going to look at how carbon dioxide is released back into the atmosphere.

Carbon is released into the atmosphere as carbon dioxide when plants and animals respire.

Cellular respiration is a chemical process that uses glucose from food as a fuel to provide energy for life processes.

The equation for respiration is glucose reacts together with oxygen to produce carbon dioxide and water.

And if we look underneath, we've got a balanced symbol equation.

The formula for glucose is C6H12O6, and one glucose molecule will react with six oxygen molecules.

So we've got 6O2, and they react together to produce 6CO2 molecules, so six carbon oxide molecules, and six water molecules.

And the formula for water is H2O.

And remember, this process of respiration happens in both plants and animals, and it's a way that carbon dioxide is released back into the atmosphere because carbon dioxide and water are the products of respiration.

Another way that carbon dioxide is released into the atmosphere is in combustion, and humans can combust fossil fuels to release energy.

An example of where we combust fossil fuels is in the generation of electricity.

And you can see in the diagram there, we've got a picture of a power station, and this is a power station that is using fossil fuels and burning them, so reacting them with oxygen to release energy that is used to generate electricity.

The equation for the combustion of a fuel is fuel, so you have your fossil fuel, react it with oxygen, and these react together to produce carbon dioxide and water.

So you can see there that the combustion of fossil fuels releases carbon dioxide back into the atmosphere.

Earlier we saw how carbon can get locked up in fossil fuels, and here we're seeing how when we burn fossil fuels, we release that carbon as carbon dioxide back into the atmosphere.

Time for a question.

What are the products of respiration and combustion? So both respiration and combustion had the same two products.

What were those products? And the products are the things that you make in those reactions.

Is it A, glucose plus oxygen? B, carbon dioxide plus oxygen.

C, carbon dioxide plus water.

Or D, fuel plus oxygen.

The products of both respiration and combustion are carbon dioxide plus water.

So well done if you chose answer C.

Another way that carbon dioxide is released into the atmosphere is by decomposition.

And decomposition is the breakdown of dead and decaying matter.

Examples of decomposers, and they are organisms that carry out decomposition, include most fungi and some bacteria.

Decomposers release carbon dioxide by the process of respiration.

Let's recap some of the ways that carbon dioxide is released back into the atmosphere: when plants and animals respire by combustion of fossil fuels and by decomposition of dead and decaying matter.

Time for a question.

Which of the following are ways carbon dioxide is released into the atmosphere? A, photosynthesis by plants.

B, respiration by plants and animals.

C, decomposition of dead matter.

Or D, dissolving in the oceans.

Choose any answers that you think are correct ways that carbon dioxide is released into the atmosphere.

The correct answers are B and C.

So well done if you remembered that respiration, which is carried out by plants and animals, and decomposition of dead matter are two ways that carbon dioxide is released into the atmosphere.

Photosynthesis removes carbon dioxide from the atmosphere and dissolving in the oceans also removes carbon dioxide from the atmosphere when it dissolves in the oceans.

Time for our final practise task of today's lesson.

What you need to do here is match the statements in those boxes to the correct stage of the carbon cycle.

So for each of those numbers from one to nine, you need to match them to the correct statement.

And you will notice that eight appears on there twice, and that's because the same process is happening at both of those points.

Pause the video now, have a go at matching these statements to the correct point on the carbon cycle and then come back when you're ready to go over the answers.

Let's see how you got on.

Number one is photosynthesis happening here, removing carbon dioxide from the atmosphere.

Number two is the carbon dioxide dissolving in the oceans.

Three is forming carbonates in shells so that dissolved carbon dioxide in the oceans can form carbonates, which are used in shells and bones.

Four is the formation of fossil fuels.

Five is that the carbon is transferred when animals eat plants and when animals eat other animals.

Six, waste material and dead organisms return carbon to the soil.

Seven is decomposition that releases carbon dioxide into the atmosphere.

Eight is the combustion of fossil fuels that also releases carbon dioxide into the atmosphere.

And number nine is plants and animals respire.

Well done if you managed to correctly match those statements with the correct stage of the carbon cycle.

We've come to the end of today's lesson, so let's just summarise some of the key points that we've covered in today's lesson.

Combustion increases the amount of carbon dioxide in the atmosphere.

Respiration of living things increases the amount of carbon dioxide in the atmosphere.

Decomposition of dead plants and animals also increases the amount of carbon dioxide in the atmosphere.

Photosynthesis, which is carried out by plants, reduces the amount of carbon dioxide in the atmosphere and carbon dioxide is also removed when it dissolves in the oceans.

You've worked really hard in today's lesson, so well done.

I've really enjoyed the lesson and I hope you have too, and I look forward to seeing you in another lesson soon.