Lesson video

This lesson is called classifying organisms using a classification key, 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 are going to explain how to use a classification key, and the importance of classifying organisms into groups within larger groups.

Now, there are a number of keywords that we're going to come across today, and they're listed on the screen now with their definitions.

You may wish to pause the video, make notes of them now if you wish to, but I'm gonna introduce them to you as we come across them throughout the lesson.

Now, in our lesson today, we're going to firstly look at classifying organisms. Then we're going to look at using a key to classify organisms before we consider the importance of classification.

So are you ready? I am.

Let's go.

So we know that scientists classify organisms according to their features, and this process of classifying is called taxonomy.

So if you are classifying anything, you are using the process of taxonomy.

And in biological classification, there are seven levels of classification: kingdom, phylum, class, order, family, genus, and species.

And as we go down that list, we have fewer organisms with more features in common and fewer differences.

And the higher up the list, we have the opposite.

We have far more organisms with far fewer similarities between them and many more differences.

So we can classify plants and animals, for instance.

So both of those are multicellular organisms. They are made up of many cells together to make the one organism.

But how do they differ? Well, plants are producers and can make their own food, whereas animals are consumers, they must eat another organism for their food.

So we can classify living organisms initially into these two groups, for instance.

So let's zoom in and have a look at animal classification.

So we take a living organism and we work out some of its key features.

And if we've decided it's an animal, then we can see whether it's a vertebrate or an invertebrate.

That means whether it's got a backbone or not.

And if we look at the vertebrate animals, then we can see that there are different classes of vertebrate animals, including amphibians, fish, reptiles, mammals, and birds.

And we can group them into their various classes.

So all vertebrates have a backbone, but how do the vertebrates differ? So let's look at the case of the amphibians, fish, reptiles, mammals, and birds, and the distinct differences between them.

So firstly, the amphibians, the fish, and the reptiles are all cold-blooded.

Their body temperature changes with the environment, whereas mammals and birds are warm-blooded.

They must keep their body temperature at about the same temperature all of the time.

Amphibians have moist skin, fish have wet scales, whereas reptiles have dry scales.

Now, mammals are covered in hair or fur and birds are covered in feathers.

Amphibians and fish use external reproduction, so their eggs and sperm are released into the environment and that's where the egg is fertilised.

Whereas for reptiles, mammals, and birds, the fertilisation process happens within the body.

So that's called internal reproduction.

And then, amphibians lay jellylike eggs in water.

Frog eggs are an example, for instance.

Whereas fish lay eggs in water, but they tend to be smaller and harder.

And reptiles lay eggs on land, which have a soft, leathery shell.

Mammals give birth to live young, and birds lay eggs with hard shells.

And then finally, amphibians have very simple lungs.

Fish use gills to breathe.

And reptiles, mammals, and birds all have lungs of various different structures.

So we can see that there are some similarities across the classes, but there are also plenty of differences that we can consider as well.

So whose idea about classification is correct? Now, Aisha says, "As we classify from kingdom to species, we get more organisms per group." Sam says, "There are fewer features in common between organisms as we move from species to kingdom." And Jacob says, "Only animals and plants are grouped by the seven levels of classification." So who is correct? I'll give you five seconds to think about it.

Okay, well hopefully you said that Sam is correct, that there are fewer features in common between organisms as we move up from species to kingdom.

Well done.

So what I'd like you to do now is to consider mammals, birds, reptiles, amphibians, and fish, and the various different features that we can use to classify them against, including body covering, how it breathes, where it lives, and how offspring are produced.

And I'd like you to complete the table to show the differences in the features for the different groups of the vertebrate animals.

Now there's information in the additional material that you can use to help you.

Pause the video and take your time.

Come back to me when you are ready.

Okay, so let's have a look at how you've organised this.

So mammals you should have said are covered in hair or fur.

Birds are covered in feathers.

Reptiles have dry scales.

Amphibians have wet skin.

And fish have hard scales.

Mammals breathe with lungs.

So do birds and reptiles.

Amphibians have simple lungs, and fish use gills to breathe.

Mammals can live mainly on land, but they do live in both.

Birds live mainly on land.

Reptiles live on land.

Amphibians can live in both, and fish live in water.

And mammals give birth to live young.

Birds lay eggs with hard shells.

Reptiles lay eggs with soft shells on land.

And amphibians lay jellylike eggs in water, with fish laying eggs in water.

So just check your work over, have you got that all right? There's quite a lot of detail there to have a look at.

Amend anything if you've made any mistakes.

And well done, that was quite a lot of information to process.

Okay, let's move on to the next part of our lesson about using a key to classify organisms. So there are some organisms which are a bit complicated to classify because they look like they might belong in several different groups.

So let's take the penguin for instance.

Laura thinks it's definitely a bird because it has feathers.

Andeep says, "But it can't fly, so it can't be a bird." Jun says, "It has wings but can't fly, so I think it's a mammal." Whereas Izzy says, "It lives on land and in the water, so it's an amphibian." But who is right? Well, if we're not sure, we can use a classification key to help us work it out.

So let's use this to help us classify a penguin.

Firstly, does it have wings? Yes, a penguin does have wings.

Does it have feathers? Yes, it does also have feathers.

Therefore a penguin must be a bird.

And that's an example of using a classification key for classifying an organism.

Let's look at a different example.

We're gonna use the same classification key, but this time to classify a bat.

So does it have wings? Yes.

Does it have feathers? No.

And therefore it must be a mammal.

Now you try.

Use the same classification key and this time group a whale.

So let's just check how you got on.

Did you say that in answer to the question does it have wings, no, it doesn't have wings.

Does it have gills and scales on its skin? No, it doesn't either.

So a whale must be a mammal.

What I'd like you to do now is to use that same approach to classify an armadillo, an ostrich, a dolphin, and a turtle.

So there's lots of things to think about when building a classification key.

It's quite a complicated process.

Think about the features that you are going to use to help you tell the animals apart and which questions would you ask that would help somebody else to decide how best to classify those animals.

And are there any features that suggest that an animal should be in one group or another? There's information in the additional materials about these organisms that you can use to help you in this task.

Now this is quite a complicated task, so do take your time, work with somebody else if you need to pick their brains too, and check the logic in your classification key, make sure it really makes sense.

Okay, come back to me when you're ready.

Okay, so hopefully you've built a key by now and your key might have had questions which have a narrow range of very specific answers like is it warm-blooded or coldblooded? Does it give birth to live young or lay eggs? Does it lay hard shelled eggs or leathery eggs? Does it have a shell or beak or feathers or scales? And those questions should have been laid out in a logical series where there's only one route for any one animal, and ultimately resulting in classifying those animals as mammals, birds, fish, reptiles, or amphibians, with the correct solutions were: an armadillo is classified as a mammal, an ostrich as a bird, a dolphin as a mammal, and a turtle as a reptile.

So for instance, your classification key might have looked a bit like this one.

So you might have started off with a question about reproduction.

Does it use internal or external reproduction? If you said internal reproduction, then is it warm-blooded or cold-blooded? If you said cold-blooded, then that would be a turtle, which is a reptile.

If you said warm-blooded, then does it have hair or fur or feathers? If you said hair or fur, then you would've chosen armadillo or dolphin, which is a mammal, or feathers, which is an ostrich.

And if you said external reproduction from the first question, then does it have moist skin or wet scales? And if you'd said moist skin, then that would've led you to amphibian.

And if you said wet scales, then that would've led you to the fish.

Or you might have used a different classification key.

So maybe your classification key looked a bit like this, starting off with, is it warm-blooded or coldblooded? If you'd said warm-blooded, then maybe you would've asked, does it give birth to live young or lay eggs with hard shells? And maybe then if you said live young, then you would've ended up with armadillo or dolphin, which are both mammals.

And if you'd said eggs with hard shells, then you would've ended up with ostrich, which is a bird.

Whereas in answer to that first question, is it warm-blooded or cold-blooded, if you'd said cold-blooded, you might have then asked, does it have lungs or gills? If you'd said gills, then it would've been fish.

If you'd said lungs, then you might've asked, does it lay eggs with soft shells on land or jellylike eggs in water? And if you'd said eggs with soft shells, then you would have ended up with a turtle, which is a reptile.

And if you said jellylike eggs, then it would've been an amphibian.

Now I'm sure your classification key would've looked something different again, but that kind of principle is what you should have worked to.

So just check your answer over against my examples and the mark scheme and just make sure that your classification key really works as a key.

Well done, by the way.

That was a really tough task to do.

So well done for persevering through that and using all that information to sort it out.

It's complicated.

So let's move on to the last section of our lesson today then, which is about the importance of classification.

So classification is very useful and it's also really important.

And it's important because it can help us organise animals, well, organisms, and it can help make sense of the biodiversity which is available on earth, of which there is incredible variety.

So for instance, these elephants which are being monitored in the wild, we can use classification to keep tabs on them and work out which species we've got and what's in the habitat, for instance.

And we can use that in conservation to track diversity, to track conservation efforts, to see whether the things that we are doing are really making a difference or not, as the case might be.

And hopefully they will be.

So let's just quickly check.

Classifying organisms is useful when monitoring biodiversity.

Is that true or false? Well, hopefully you said that's true, but why did you say that's true? So justify your answer.

Well, hopefully you selected the fact that it accurately describes the features of an organism, which is useful in conservation.

Now this next task requires you to decide, make some decisions for yourself, because what I'd like you to do is to sort the nine different reasons for classification into a diamond nine.

Now, the diamond nine has this very specific layout where you have the most important at the top, the least important at the bottom, and then two options on the second and the fourth layer and three options in the middle, all of equal value.

So take the nine reasons listed here on the screen and sort them into what you think is the most important, the least important, and the various grades in between.

Now this is your decision, so what you come up with may well be different from the people around you and it may well be different from what I have as well.

That doesn't matter.

What matters is your ability to explain why you have chosen to sort them as you have.

So think about how you're going to sort them and make some real careful decisions about why you are putting the most important at the top, the least important at the bottom.

And make sure you can explain your reasoning for that.

So take your time over this task and really think about it.

Give it some good consideration.

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

Okay, so when you were doing this task, you should have put the most important at the top, the least important at the bottom.

And your response should have included all nine statements sorted from one to nine in whatever order you preferred with a justification for putting the first in the first point and the last in the last place.

So for instance, you might have organised your options like I have here on the screen.

Maybe putting allows conservation efforts to be planned and targeted first and reminding us of basic characteristics as the least important reason for classification, with the other options organised somewhere in between.

What matters then is your justification.

So I have chosen to put allows conservation efforts to be planned and targeted as the most important reason for classification because scientists need to know the exact organism so that the best conservation work can be completed and the information shared effectively.

And I've said that reminding us of basic characteristics is the least important reason for classification because these characteristics are usually visible and the descriptions can be quite basic.

So they're my reasons and justifications.

Just review yours.

They don't have to be the same at all as mine, but they have to be decent explanations, not just because I wanted it to be.

And well done again.

That was a really tricky task.

It requires quite a lot of thought to take a standpoint on something and then justify it clearly.

So that's a hard task and well done for persevering with that.

So in our lesson today, just to recap, we've seen that classification or taxonomy is the process of sorting organisms into groups and subgroups based on their similarities and their differences, and that we can use a classification key to help us sort organisms into the correct group using questions about their features, which help us to decide one organism from another.

We've also seen that classifying organisms is really important and very useful.

There are many good reasons for classifying organisms, including the fact that it helps us to organise and make sense of the biodiversity that is present on earth.

So I hope you've enjoyed our lesson today.

I have.

Thank you very much for joining me and I hope to see you again soon.

Bye.