Lesson video

This lesson is called classification at the cellular level and is from the unit species and classification, differences between species.

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

In our lesson today we're going to identify cell features that can be used to classify organisms into the kingdoms of animals, plants, fungi, and bacteria.

Now in our lesson we're going to cover a number of keywords and you can see the keywords and the definitions on the screen.

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

So in our lesson today, we're going to have a look at the features of a cell and just recap that information before we look at how we use those features to classify organisms. So are you ready to go? I am, let's get started.

So to remind you that cells form the basis of every living organism.

If it doesn't have a cell, it cannot be a living organism.

And, some organisms are single-cellular, they're may up of only one cell.

Bacteria are good examples of single-celled or unicellular organisms. Whereas, many organisms are made up of many many cells, these are multicellular organisms. Plants and animals are good examples of those for instance.

Now a cell contains many different parts, each of which has a specific function to carry out life processes for the cell, to enable it to live.

So, the basic features of every cell are a cell membrane, which acts as a boundary to the cell and controls the entrance and exit of substances into and out of the cell.

The cytoplasm, which is the jelly-like substance, making up the bulk of the cell.

And DNA, which is stored in the form of chromosomes.

So these are the basic features of a cell and every cell will have a cell membrane, cytoplasm, and DNA.

Now let's take the bacterium.

A bacterium is a very simple cell, and in addition to those basic features, a bacterial cell will also contain a cell wall.

Now, a bacterium does not have a nucleus, so the DNA is stored within the cytoplasm.

And, many bacteria also have one or more flagella.

The flagella are whip-like tails which help to drive bacteria through a liquid environment.

So not all bacteria have flagella, but many of them do.

Now, animals cells are more complicated cells, but they do not have a cell wall.

Now, they do have the basic features of a cell membrane, cytoplasm, and DNA, and that DNA is stored within a nucleus.

Animal cells also have mitochondria which help release energy from food.

So let's have a quick check of understanding.

Which of these cell features are present in animal cells? The cell membrane, the nucleus, the cell wall, or the flagellum, which do you think? I'll give you five seconds to decide.

Okay, so hopefully you've identified the fact that the cell membrane and the nucleus are the two features in that list which are present in animal cells.

Well done.

So let's have a look at plant cells now.

So plant cells have those same basic cell features, cell membrane, cytoplasm, and DNA, but in addition to that, they have the same parts as an animal cell.

So they have DNA stored within the nucleus and the also have mitochondria, and they also have additional features.

So they also have a cell wall which provides some structural integrity and rigidity to the cell, they have chloroplasts so they can make their own food, and they have a large, permanent vacuole which is a storage unit and also provides some reinforcement to the cell as well.

So these are the features which are found within plant cells.

Fungal cells, once again, have the basic cell features of a cell membrane, cytoplasm, and DNA, and their DNA is stored within the nucleus, just like the animal cell, and they also have mitochondria, just like the animal cell.

They also have some extra features.

So, they also have a cell wall, like the plant does, and they also have small, permanent vacuoles, but these are small vacuoles rather than a large one, and they often have many of these small vacuoles within their cell rather than one large one like the plant does.

So these are the basic features of a fungal cell.

So let's have a quick check of understanding.

What type of cell am I? I have a cell wall, I have small vacuoles, and I have DNA in a nucleus.

I'll give you five seconds to decide.

Okay, so all of these three examples, the plant, the bacterium, and the fungal cell have a cell wall.

The small vacuoles would be present in bacteria and fungi, and we can exclude the bacterium because it doesn't have its DNA in a nucleus, but we can exclude the plant cell because that has one large vacuole rather than many small vacuoles.

So the correct answer is the fungal cell.

Did you get that one right? Well done if you did.

What I'd like you to do now is to complete the table to show which cellular features are present in each kingdom.

You've got animal, plant, fungi, and bacteria, and the criteria are about having a nucleus, a cell wall, and chloroplasts.

So take your time, think about it, apply what you understand already, and complete the table, come back to me when you're ready.

Okay, let's check how you've answered this table.

So you should've said that an animal cell has a nucleus, so does a plant, so does a fungi, but a bacterial cell does not.

You should've said that an animal cell does not have a cell wall, but a plant cell does, so do fungi cells, so do bacterial cells.

And you should've said that an animal cell does not have chloroplasts and therefore can't make its own food, but a plant does, fungi don't, and neither do bacteria.

So just check the ticks and crosses, make sure you've completed the table correctly, make any amendments if you need to, just make sure that's really clear because sometimes ticks and crosses and crosses and ticks, they're all rather confusing, so make sure your table is nice and neatly filled in and well done indeed for applying your knowledge to this form.

Okay, let's move on then to see how we can use those cellular features to classify organisms. So, we know that classification involves sorting out organisms into different groups and sub-groups based on characteristics that they share and differences that they have between each other.

And we classify organisms firstly into a kingdom, animal kingdom, plants kingdom, fungi kingdom, and the bacterial kingdom.

So these are major kingdoms that we can put organisms into.

Now, we can classify those organisms based on a number of different features.

But, we can use the features of the cells that make up that organism to classify them with great accuracy.

So, we can use the cell features to classify organisms into the animal kingdom, the plant kingdom, the fungal kingdom, or the bacterial kingdom using the features that are present or absent within the cells that make up that organism.

So, we can therefore put that information into a classification key.

So, let's see for instance.

Does it have a nucleus? No? Then it's a bacterial cell.

Yes? Well, is there a cell wall present? If the answer is no, then it's an animal cell.

If the answer is yes, then maybe can it make its own food? If the answer is no, then it's a fungal cell, and if the answer is yes, then it's a plant cell.

So we've used the features of the cell to classify it using a series of questions within a classification key.

So, let's just see.

Scientists have discovered this new organism which looks like a green blob, as you can see in the picture.

So what I'd like you to do is to use the features in the table below to decide whether it is a plant or an animal.

So what do you think? Do the features suggest that it's a plant, an animal, or does it not help you to decide at all? I'll give you five seconds to think about this, but actually you'll need to pause the video and spend a wee bit longer than that, and then come back to me when you're ready.

So let's have a look then.

The feature of it being green, now does that suggest it's a plant or an animal, or does that not help you to decide? Well I would suggest that doesn't help you to decide because, yes many plants are green, but there are also many plants which are not green, purple-leaved trees for instance.

And, there are many animals which are green, frogs and snakes to name a couple of examples.

What about it not having roots? Well, I don't think that helps you really either because whilst many plants have roots, there are other plants which do not, so tumbleweed for instance doesn't really have a root and air plants don't either.

So it's not really an exclusive animal feature.

It does not have fur.

Well again, I don't really think that helps you to decide because there are many animals which don't have fur and there are some very, very furry plants.

What about it not having legs? Hm, well I don't think that helps you to decide either because there are many animals which don't have legs, and, obviously plants don't have legs, but it doesn't really rule out animals, does it, because many, many animals do not have legs.

And, it is soft and squidgy.

Well, again, there are many animals which are soft and squidgy, slugs for instance, but there are many animals which are not soft and squidgy, and plants, well, there are many plants which are soft and squidgy.

I mean, many of them are hard aren't they, and tough, like trees and shrubs, but there are plenty which are fairly soft and squidgy as well.

So I don't really think that helps you to decide either.

So let's have a look at how we might use the cellular features of an organism to correctly classify it instead.

We can see that actually using the cellular features of an organism will give us a more precise method of classifying organisms rather than using their appearance alone, because as we've just seen, using just their appearance doesn't necessarily rule in or out any organisms. So let's have a look at the questions here.

See whether these help us to decide whether this organism is a plant or an animal, whether this is any easier.

So again, you might need to pause the video for a little bit to study the example and the questions of the features to decide whether it's a plant or an animal or whether these don't help you to decide either.

Come back to me when you're ready.

Okay, so let's have a look at this organism again using the cellular features of it.

So its cells have a cell wall.

Well straight away that rules out an animal doesn't it, because animals don't have cell walls, their cells do not have a cell wall.

So that suggests that this organism is a plant rather than an animal.

What about its cells making their own food? Well animals are heterotrophs, that means that they have to eat other organisms in order to get food, whereas plants are autotrophic, that means that they can make their own food and therefore their cells must be able to make their own food.

So that, again, suggests that they are a plant.

And, the cells contain chloroplasts, so we can see that in the magnified image there, we can see those little green circles within the bigger green circles.

So the big green circles are the cells and then the little ones are the chloroplasts, and so these cells contain chloroplasts and that really does suggest that it's a plant, certainly not an animal anyway.

So overall, the information from the cellular details suggest that this new organism is a plant as opposed to an animal.

So what I'd like you to do now is to create your own cell.

Now you can be as crazy and wild and inventive and creative as you absolutely like, but, you need to decide which parts of the cell it will and will not have and what job will it do.

So really go creative, really go wild on this.

Once you've decided what your cell is going to be and what parts it's going to have and not have, I want you to draw it, make it nice and colourful and label it as well.

Label all the cellular features on it.

And then once you've done that, classify it.

Is it a plant, an animal, a fungus, or a bacterial cell? And I'd like you to explain why you have classified it as you have using the features that it does or does not have.

So spend a good amount of time being really creative, having a bit of fun with this task, adding in the scientific information as well, and come back to me when you're ready with your super duper creations.

Okay, well I hope you enjoyed that because I certainly did.

So here's my creation and I'm sure you have come up with some absolutely stupendous creations as well.

Now the important thing in addition to the funky cells that you've created is to make sure that you've labelled the appropriate parts to allow it to be classified.

So in my example, I have included a nucleus, I have also included a cell wall which has these really cool defensive spikes, and I've also included some small vacuoles which, in my vacuoles, they contain poison.

And so my conclusion and classification is that this organism that I've created is a fungal cell because it has a cell wall, it has a nucleus, and it also contains small vacuoles, mine are filled with poison.

It also is a fungal cell because it does not have chloroplasts, so it cannot make its own food.

It has to get its food from somewhere else.

So you can see how I've justified the classification of my cell based on the features that it does and does not have, and I'm hoping that you have done the same with your creations too.

Okay, I hope you enjoyed that, I really did.

So let's just summarise our lesson today.

We have seen that classification involves grouping organisms based on their shared features and their distinct differences, and that all cells have the same three key features, a cell membrane, cytoplasm, and DNA.

But we've also seen that there are other features of cells that are present in some and absent in other cells, which distinguish one kingdom of cells from others.

And these features include chloroplasts, cell wall, presence or absence of a nucleus, presence of mitochondria, and the type of vacuoles and the size of vacuoles and how many of them there are.

And that by using the cellular features, we can group organisms into the kingdoms of animal, plant, fungi, or bacteria with greater accuracy than we might be able to do if we just go on appearance alone.

So thank you very much for joining me and I hope you've had fun, and I look forward to seeing you again soon, bye.