Lesson video

- Welcome to today's Oak Academy science lesson.

My name is Mrs. Boes, and to make sure we're ready to start this lesson, have in front of you a pen and some paper and be ready to go.

Today's lesson is called, "Unicellular organisms" and the outcome is to define unicellular organisms, describe some of their common features and identify their uses and dangers, and this fits into our science topic at key stage three called, cells.

The keywords for today's lesson.

These words will help us to understand some of the concepts that come up within the lesson.

The first one is bacteria.

And a bacteria is a microorganism that is unicellular.

Fermentation is a process that converts sugar into alcohol.

And a subcellular structure is contained within a cell.

So if you have a cell, there are many little subcellular structures that make up that one cell.

So those are our keywords, bacteria, fermentation and subcellular.

The outline of today's lesson on unicellular organisms is, the first thing we're gonna do is define and give examples of unicellular organisms. The second thing we will learn, is some common features of unicellular organisms. And then finally, we're going to look at some uses and some dangers of those unicellular organisms. But to start with, we're just gonna define and give some examples of unicellular organisms. So let's get going.

Let's start by looking at the definition of unicellular and the prefix, uni.

Uni means one.

If we think of some other words that have the prefix uni, there is a unicycle, which has one wheel, a unicorn, which has one really big horn coming out of its head.

If you are unified, it means you make as one.

You come together as one if you are unified.

And if I asked you to say something in unison with me, it would mean that we make one sound together.

So uni means one.

And cellular means a living cell.

So therefore, the definition of a unicellular organism is that they are living things made up of only one cell.

Yeast, amoebas and bacteria are unicellular organisms. They're the three different unicellular organisms we're gonna be looking at today.

So if they're unicellular, it means they're made up of one cell and they're all living cells.

So first we'll look at a yeast.

You might have heard of yeast before.

If you've done a bit of baking, you could have heard of some yeast.

This is an amoeba.

Now, amoebas a very interesting, you can see they've got quite a different shape to the yeast cell and those kind of projections that are coming out of the amoeba, they can help the ameba to change shape.

And then the final unicellular organism is the bacteria cell, and I'm sure you've probably heard of bacteria before.

But again, they're unicellular.

So the yeast, amoeba and bacteria cells, they only consist of one cell and they're all living.

So they are unicellular organisms. Let's see how much we have learned so far.

So the question is, which statement is correct? A, unicellular organisms are alive and made of many cells.

Unicellular organisms are dead and made of one cell, or unicellular organisms are alive and made of only one cell.

You have a go, see if you can see which one it is.

Of course, it's C, because unicellular organisms are alive and they're made up of only one cell.

Should we try another one? Which of the following is not a unicellular organism? A, amoeba.

B, a cactus.

Or C, a bacteria.

You have a go.

Hopefully you've got B, which is a cactus, because we said that amoeba, bacteria and yeast were all unicellular organisms. Time for us to try your first task.

So you need to fill in the gaps using the words below on your sheet.

So the words that you'll be using are one, living and unicellular.

If you pause the video now to give yourself time to finish that task and then press play again when you're ready to go.

Let's go through the answers.

So the first fill, unicellular organisms are made up of one cell.

The word uni means one and the word cellular means living cell.

So give those a mark.

See how many of them you got right, and well done if you did get them right.

That's brilliant.

Our second task.

Draw a line to match the unicellular organism to its name.

So you just really simply need to draw a line from each picture and match it to the correct name for that organism.

Pause the video now and then press play again when you're ready to go.

Let's go through the answers.

So if we start with the first cell, that's a yeast cell.

Our second cell was the amoeba.

Remember we said that it's got those projections that come out that can help it to change shape.

And then the final cell is our bacteria cell.

Really well done if you've got all of those right.

Okay, so we have finished our first learning cycle.

We should be able to define and give examples of unicellular organisms. Now, the next part of the lesson is to look at some common features of unicellular organisms. So let's get going.

So this is a yeast cell and there are some subcellular structures that are common between yeast, amoeba and bacteria cells and there are other subcellular features that are different.

And we're gonna look at the subcellular features within each of those cells.

Now remember, a subcellular structure is a smaller part that makes up a cell.

So we are looking at the smaller parts within this whole kind of oval shape.

So this is a yeast cell.

On the very, very outside of the yeast is something called a cell membrane, and the cell membrane surrounds the whole outside of the yeast cell and it controls what can come in and out of that cell.

It's also got a nucleus, which is this kind of bigger circle towards the top.

The nucleus contains the DNA and it controls the cell's activities.

It's very important.

And then the cytoplasm is a jelly-like substance that surrounds all of the subcellular structures within that cell.

And it's where lots of the chemical reactions take place.

And then the yeast also has something called a vacuole, which you can see down here is just at the bottom of this picture.

And then you can see, this word here can be a little bit complicated to say, but it's mitochondria.

The mitochondria are very important, because this is where energy from respiration is released.

If we look now at an amoeba cell.

There are many similar subcellular structures.

Again, the very, very outside of the amoeba cell is called the cell membrane.

The amoeba's also got a vacuole within it, the jelly-like substance that surrounds all of the subcellular structures, the cytoplasm is also in the amoeba.

And again, like the yeast cell, it's also got a nucleus which contains the DNA.

So really, although the subcellular structures are very similar, the shape of the amoeba is different to the yeast cell but they do contain very similar structures within them.

The bacteria cell however, is a little bit different to our yeast and our amoeba cell.

It does still have a cell membrane, but if you notice around the very outside of this bacteria, there's also another layer that surrounds this cell and that is called the cell wall.

So there's an additional subcellular feature in the bacteria.

It's still got the cytoplasm, the jelly-like substance that surrounds all the subcellular structures.

However, the bacteria doesn't have a nucleus, instead it's DNA is in this big long loop which is floating inside of the cytoplasm.

So the yeast and the amoeba cell both have the DNA inside the nucleus, but a bacteria cell just has a big loop of DNA within the cytoplasm.

Right, let's have a look and see how much of that you have remembered and just give it your best go.

So the first task, can you please complete the two missing labels on this yeast cell? Ready, should we go through the answers? The first one is our mitochondria and our second structure is the cytoplasm, that jelly-like substance we spoke about.

Well done if you got those right.

We're ready for the next question.

Complete the two missing labels on this bacteria cell.

Now, you have a go now.

Let's check.

So number one, that's our DNA loop or loop of DNA.

Remember, bacteria cells don't have a nucleus.

The DNA is just floating in the cytoplasm.

And then number two, that's the cell wall.

The cell wall is the very outer layer of bacteria cell, because a cell membrane is just inside of it.

Now, the final two.

Can you complete these two missing labels for the amoeba? Let's check.

So for number one, you should've had the nucleus and for the number two, it's the vacuole.

Really great job if you've managed to identify all of those subcellular structures.

One more question.

So which statement is correct? A, yeast cells have a cell wall.

B, yeast and amoeba have a vacuole.

C, bacteria, yeast and amoeba have a nucleus.

I'll give you a little bit of time to think about this one.

It's B.

Both yeast and amoeba do have a vacuole.

Next question.

Which two subcellular structures do bacteria, amoeba and yeast all have in common? A, nucleus and cytoplasm.

B, the cytoplasm and cell wall.

Or C, cytoplasm and cell membrane.

It's C, the cytoplasm and the cell membrane.

Really well done if you remembered that.

On to task two now.

So your job on the sheet is to label the images of unicellular organisms using the key terms. Some of the words below might be used twice.

Pause the video now and then press play when you're ready for me to go through the answers.

Well done if you managed to finish that.

Let's go through the answers now.

So on your yeast cell, you should have a cell membrane, nucleus, cytoplasm, the vacuole and the mitochondria.

I'll just give you a second to make sure that you've marked all of those.

And then on the bacteria cell, you've got the cell membrane, the cell wall on the very outside of the bacteria, the DNA loop rather than having a nucleus, and the cytoplasm.

Brilliant job if you managed to get all of those right.

We're ready now to move on to our final learning cycle of the lesson, which is where we talk about some uses and some dangers of unicellular organisms. So first, we're gonna start with some uses of yeast.

Now, yeast can be used in baking and it produces carbon dioxide which causes baking products to rise.

Carbon dioxide is a gas and if you've done any baking at home, you might have seen when you're making a cake, for example, that the mixture that you put in the tin is quite flat and then as the cake is cooking, it starts to rise up.

And that is because there's yeast in there which produces carbon dioxide and causes the baking product to rise.

Yeast can also be used to make alcohol, because yeast can turn sugar into alcohol, and that is called fermentation.

So some of you might already know, but if you wanted to make cider, which is the type of alcohol, you would use apples.

Apples contain quite a lot of sugar and if you added yeast over time to the fermentation process, then the sugar in the apples would turn into cider.

Similarly, grapes are used to make wine and grapes contain lots of sugar, which when you add yeast to them in fermentation, it would turn into the wine that we drink.

Now we're gonna look at some uses of bacteria.

Bacteria can be used to make yoghourt and cheese.

Now, not all bacteria are used to make yoghourt and cheese, just some, because some bacteria are really, really good at turning milk and making it kind of stick together and coagulate together so it's a little bit thicker.

And those bacteria are useful, because they make that milk turn into yoghourt and if you left it a bit longer, it would turn into cheese.

Now, some bacteria are in our digestive system.

So our digestive system is full of trillions of bacteria.

There's actually 300 to 400 trillion bacteria in the human gut, which is about three to four times more bacteria in the gut than there are cells in the body.

And that's because bacteria cells are a lot smaller than animal cells, but we have a lot of bacteria that are really good in our digestive system.

We have lots of useful bacteria in our digestive system that help us to digest our food and they're brilliant.

They are supposed to be there, they're really helpful.

However, there are also some bacteria that are dangerous and they cause illness and disease.

So if for example, you eat some food that is potentially undercooked or has just got bacteria on it and it goes down into your digestive system, those bacteria can potentially cause quite serious illness.

So salmonella and food poisoning, those are caused by bacteria that shouldn't be in our digestive system that then are in our digestive system and cause illness.

Let's check what we have understood about our uses and dangers of unicellular organisms. So first question.

What gas does yeast produce to make bread rise? A, carbon dioxide.

B, oxygen.

Or C, nitrogen? Well done.

It's A, it's carbon dioxide.

True or false.

All bacteria cause disease.

True or false, and justify your answer.

A, we have some good bacteria in our digestive system that help us to digest food, or B, bacteria are dangerous, because they enter our digestive system and cause illness.

Let's check.

You should have had false.

Not all bacteria cause disease, because it's A, we do have some good bacteria in our digestive system that help us to digest food.

So not all bacteria cause disease.

Which of the following is not a use of bacteria? A, making cheese.

B, making alcohol.

Or C, making yoghourt.

You should have had making alcohol.

Remember, yeast is used to make alcohol.

Bacteria is used to make cheese and yoghourt.

Let's move on to task three of today.

So answer the following questions in full sentences.

Now pause the video now and when you finish the task, if you press play again, I'll go through the answers.

Let's go through the answers then.

So the first question, name two types of food that are made using bacteria.

Bacteria can be used to make cheese and yoghourt.

B, bacteria can be harmful, why? Bacteria can be dangerous, because they can cause illness and disease.

Now, you might have also written something about the digestive system there or given a specific example such as salmonella or food poisoning, and that's brilliant.

Question C, explain why yeast is used in baking.

Yeast is used in baking as it produces carbon dioxide, which causes baking products to rise.

And finally, D, explain why yeast is used to make alcohol.

Yeast is used to make alcohol as it turns sugar into alcohol.

This process is called fermentation.

Absolutely brilliant if you managed to answer lots of those correctly.

If there's anything that you've missed off, pause the video now and own your work and improve it adding any extra information.

Right, well that's actually the end of today's learning.

We're just gonna do a summary now of everything that we have learned about unicellular organisms. So the first thing we learned, was that unicellular organisms are made up of only one cell and that they're living.

The three examples of unicellular organisms are bacteria, amoeba and yeast.

Some features of these cells are common, but others are different.

Remember that our bacteria cell did not have a nucleus and it also had a cell wall.

Some bacteria in our digestive system help to digest food, but some bacteria caused illness and disease.

Bacteria are used to make cheese and yoghourt and yeast is used to make alcohol and in baking.

That's the end of today's lesson.

There is an exit quiz for you to have a go at afterwards, and I'm sure you're all gonna do really, really well.

I hope you've enjoyed it today and you've also learnt lots as well.

I will see you next time.

Bye.