Lesson video

Hello, and today's lesson is from the Unit: Classification in modern biology.

And the lesson title is Classification into kingdoms and domains.

Hiya, my name's Dr.

Pugh, and I'll be taking you through today's lesson.

Okay, let's look at the lesson outcome for today.

So by the end of this lesson, you should be able to describe the classification of organisms based on evidence from their phenotype and cells, and that's gonna require a number of keywords for the lesson, which we can see here.

And the keywords that we're gonna be using frequently are species, kingdom, domain, and phenotype.

Now, the definitions are there for you to have a look at.

I'm not gonna read them through with you, but if you'd like to pause the video now, do so, and you can make notes or you can copy them from the slide.

Okay, so let's look at the lesson outline, and the lesson's gonna come in three parts today.

The first part is called Linnaean classification, the second part is looking at the binomial naming system of living organisms, and the third part is looking at the three-domain system of classification.

So let's start with Linnaean classification.

So what is the Linnaean system of classification? Well, the Linnaean system of classification was invented by a Swedish botanist called Carl Linnaeus in the 18th century.

He's often called the father of the modern classification system.

He started sorting organisms that have similar phenotypes into groups.

By phenotypes, I mean organisms with similar physical appearances.

So what Linnaeus did was he identified three large groups from nature, which he referred to as kingdoms. The things in each kingdom grow, right? So his initial kingdoms were as follows: The plant kingdom, the animal kingdom, and surprising to us today, the mineral kingdom.

Now, which of those do you think is the odd name out? Which isn't a kingdom? And it's one that Linnaeus actually removed from his first publication.

I think you've got the right idea that he removed the mineral kingdom, because although minerals grow, they aren't alive.

So what Linnaeus is doing, he's classifying organisms based on the observable and measurable characteristic of organisms. Okay, let's do a quick check on Linnaean classifications.

So what is the name of the 18th-century botanist who developed a system for classifying living things? If you'd like to pause the video now, I'll give you the answer in a moment.

Okay, so if you answered Charles Darwin, you would be wrong.

Gregor Mendel, incorrect.

Jean-Baptiste de Lamarck, also incorrect.

The answer is d, Carl Linnaeus.

So well done if you got that answer.

Right, how did Linnaeus classify organisms? Again, you've got three choices, so pause the video now, enter your choice.

Okay, so if you picked a, that's incorrect.

He didn't use their genotypes.

He didn't use their names, but he did use the phenotypes, the observable and measurable physical characteristics.

Okay, so let's look at what Linnaeus did next.

So Linnaeus has his kingdoms. He then began to subdivide the kingdoms into smaller and smaller groups.

And in each of these groups, the characteristics get more similar as the groups get smaller.

So let's look at the example on the slide here.

We've got kingdom animalia, or kingdom animals, and you can see we've got a real range from lions, tigers, all the way through to fish, birds, and worms. The next grouping is the phylum, okay? So the phylum, in this case, we're looking at the phylum chordata.

So what we're doing is we're classifying organisms with a backbone, with a vertebrae.

And you can see here that straight away, we got rid of the worms, which are invertebrates.

That is, they don't have a backbone.

So the next grouping is the class, and the class here is mammalia.

Mammals are living organisms with fur, and they produce milk to feed their young.

And from this, we've got rid of the fish and the birds, and we're down to is mammalia the tiger, the cat, the dog, the polar bear, the rabbit and the human, one of which belong to the mammalia class.

Next grouping is order.

And here we've got the order, carnivore.

So carnivorous animals, they're the ones that only eat meat.

We've got the lion, the tiger, the cat, the dog and the polar bear.

Next grouping is family, here we got felidae.

So we've got lion, tiger, domestic cat.

The last two categories are firstly genus, which here we've got panthera.

So panthera is the grouping of the big cats, the lion and the tigers.

And finally, the smallest grouping is the species, and in this case it's leo.

And the species is the most basic unit of classification, groups of similar organisms which can inter-breed to produce fertile offspring.

Okay, so how do we remember this system of classification? How do we remember kingdom, phylum, class, order, family, genus, species? Well, using a mnemonic to help.

And there's a fairly decent one here that you can use, by all means, come up with your own.

It's a really useful way of remembering the sequence of these words.

So what I'm going to show you now is one that I've got; King, Philip, Came, Over, For, Good, Soup.

So kingdom, phylum, class, order, family, genus, species.

And there's the king having a nice bowl of soup there.

Okay, so let's do a little bit of a knowledge check here.

We'll do it like this.

We've got a missing word there.

So we've got Over.

So O is for Order.

P, is Phylum.

Got a number of them missing here.

So King Philip Came Over.

So C for Class.

Over Order.

For Family.

Good Genus.

Species.

Okay, so let's do some practise questions.

So firstly, I'd like you to define the term classification.

Secondly, how did Linnaeus classify organisms? And using your mnemonic, starting with the largest group, put the groups in the classification system into the correct order.

Now pause the video and we'll join up a little bit later to go through the answers.

Okay, let's go through the answers.

So the first question was define the term classification.

Classification is the process of sorting organisms into groups based on their characteristics.

Number 2, how did Linnaeus classify organisms? He classified organisms by the observable characteristics their so-called phenotypes.

And starting with the largest group, put the groups in the classification system into the correct order.

And we have kingdoms, phylum, class, order, family, genus and species.

Well done forgetting those in the right order.

You may have used the mnemonic to answer that question.

Okay, let's have a look at this practise question.

So I'll read through it and then you can have a go at answering the questions.

So the Madagascan fossa was originally classified as a cat.

So firstly, can you suggest why it was classified as a cat? And secondly, can you give one piece of evidence that shows that the fossa is not a cat? So pause the video, we'll go through answers in a moment.

Okay, so firstly, suggest why it was classified as a cat.

So hopefully you've picked out some of the observable physical characteristics of fur, whiskers, eye position, teeth.

Give one piece of evidence that shows that the fossa is not a cat, is more physical maybe.

Different ear shape, face shape, body shape is different.

And this come back to one of the problems with Linnaean classification that sometimes organisms with very similar physical characteristics can be quite unrelated.

Okay, so let's look at the binomial naming system So what Linnaeus did, he introduced the system, the binomial system of classification which each organism is given the two-part name.

The first part of the name is the genus name.

The second part is their species.

So let's have a look at some examples here.

So we've got Panthera leo, the lion.

Homo sapien, humans.

We've got Cryptoprocta ferox.

Now you can see that in each of these the first word, the genus word, is given a capital letter The second word is given specific or species name and that is given a lowercase letter.

You can also see that the the words are italicised.

So let's just expand on that and go into that a little bit more detail.

So let's look at the formatting conventions for genus and species names using the crocodile as an example.

So we've got Crocodylus nileticus.

So the first word is the genus and the first letter is capitalised.

The second word is the species name and notice it's all lowercase.

Just to review that again, genus name is capitalised, the species name is lowercase.

Now either both words are italicised or not italicised, they need to be underlined.

So let's have a look at some binomial names that have been incorrectly formatted.

So we've got the English Oak on the left, we got the Common Blackbird on the right.

And the English Oak quercus Robur, you can see that although it's underlined, which will be correct, because it isn't italicised, the first letter of the genus Q should be a capital letter.

So it should be a capital Q.

The species name, Robur should be lowercase.

Now let's look at the Common Blackbird.

Now the generic name we can see begins with a capital T, so that's correct, it's all italicised, also correct, but Merula, the species name, has a capital M and that is incorrect.

It should have a lowercase letter.

A lowercase M.

There's the incorrect letters highlighted there.

Right, so let's do a quick knowledge check.

So what I'd like you to do is to identify the correct binomial name for Felis catus.

So pause the video, make your choice and we'll go through the answer in a moment.

Okay, so let's look at a, Felis Catus.

So hopefully, you didn't put that down, because although the Felis and the Catus are italicised, you can see that the Catus, the species now begins with the capital letter.

b, the generic name begins with a lowercase letter, so that's incorrect.

c, although it's not italicised, it is underlined.

As you can see that genus name has a capital F and the species name has a lowercase C.

There we go.

Okay, so let's have a little go with a different organism.

So let's check your knowledge.

Which example correctly shows the binomial genus and species named for the dolphin Delphinidae delphis.

So pause the video, have a go at identifying the correct binomial name.

I'll give you the correct answer in a moment.

Okay, so if you chose a as the correct name you would be wrong, because although it's italicised, delphis, the species name, has a capital D, not a lowercase D.

b, is Delphinidae delphis.

Capital letter for the genus name and lowercase letter for the species name.

So that looks correct.

So let's just see if c, c is underlined, because it's not italicised, however, the species name has a capital letter that is incorrect.

So correct answer is b.

Okay, so let's practise the binomial naming system by looking at two very closely related organisms there.

The lion and tiger, Panthera leo and Panthera tigris.

Can you complete the table to show how they are classified? Now you might wanna use your mnemonic again, so you fill in the left-hand column, but pause the video, fill in the table and we'll go through the correct answers in a moment or two.

Okay, so let's fill in that table.

So lion and tiger are both animals, so kingdom animalia.

Now looking at the levels we go kingdom, phylum, class, order, family, genus, species.

So phylum, chordata, both chordata.

Class mammalia, order carnivora.

Family felidae, they're cats.

Genus panthera, panthera.

And species leo for lion, tigris for the tiger.

So well done if you've got all of those correct, especially the correct sequence of levels in the left-hand column.

Let's look at the three-domain system of classification.

So as I previously highlighted, there are some problems with the Linnaean classification system.

When you've got organisms which are closely related, but don't share common physical traits, or animals which look completely unrelated, but actually are quite closely related.

Advances in modern scientific methods such as microscopy and gene sequencing have refined classification and in a way made it more accurate.

Now the pioneer here for this was a scientist called Carl Woese who in 1970s began looking at DNA sequences from the genes of organisms and his theory was based on the following hypothesis that DNA sequences in some genes change very slowly over time.

So organisms which are very closely related will have fewer differences in DNA sequence in those genes than organisms which are more distally related, which will have more differences in DNA sequences.

And this is illustrated here.

So what he did is he compared the DNA sequences of different bacterial species.

Now bacterial species, different species can look very, very similar.

I mean it's very difficult to use physical characteristics to classify bacteria and prior to Woese, where the bacteria were kind of logged into the kingdom bacteria, however, he began to look at sequence similarities as sequence differences.

An example is given here.

So we can see two bacterial species, the DNA sequence from a particular gene and you can see that there's one difference.

There is one letter, there is one base difference between those sequences.

So that means that these two bacterial species are very closely related.

If we look at two other bacterial species, we can see here that there are no differences.

So these two species are gonna be more distantly related, because there are more differences in the DNA sequence in this gene than between the top two bacteria.

So here's a evidence from gene sequencing.

Those introduced domains which are a higher classification of above kingdoms. Domains divide living organisms into the following: Firstly, the eukaryota, this includes all animals, plants, fungi and protists.

The second domain are tree bacteria.

And the third domain are bacteria called archaea which live in extreme environments of the earth.

For example, they survive in conditions of high temperature or high acidity.

And this may reflect the bacteria from which they evolved, which were found in the conditions of the early earth.

So let's look at that three-domain system in a little bit more detail.

So let's look at the new eukaryota domain, we can see it here.

Now the animal kingdom, plant kingdom, and fungi kingdom, and protist kingdoms are all contained within the domain of eukaryota.

So all of these organisms have cells which have membrane-bound subcellular structures such as a nucleus.

The bacterial kingdom is contained within the domain bacteria and the archaea kingdom is contained within domain archaea.

Okay, so let's do a quick knowledge check.

So who developed a three-domain system of classification? If you pause your video now, make your selection and I'll feedback the answer in a moment.

Okay, so hopefully you chose c, Carl Woese, for the answer there.

Let's have a go at another one.

So what evidence did Carl Woese use when developing the three-domain system of classification? Was it phenotypic characteristics, genetic similarities and differences, or binomial names? So pause the video, make your selection, I'll go through the answer in a moment.

Okay, so what he did, he used genetic similarities and differences.

Well done, you've got the right answer.

Another check, which domain is the common frog in? Is it eukaryota, bacteria or archaea? Pause the video make your selection, I'll feedback the answer in a tick.

Okay, the correct answer is eukaryota, multicellular cells possessing a nucleus.

All right, so well done if you've got that right.

Now let's have a go at this one.

Which domain is the e.

coli in? Now just to give you a little bit more background information, you would find e.

coli in your intestines.

So which choice are you going to make? Are you gonna say it's a eukaryote, is a true bacteria or an archaea? Pause a video, have a think, make a selection, I'll feedback in a moment.

Okay, so the correct answer is it is a true bacteria and it's found in your large intestine, and that would be under conditions of around about 37 degrees C, whereas actually in archaea it could be in temperatures up to 100 degrees Celsius, right? Another question for you, which domain is the euglena in? So pause the video, make your selection, I'll give you the right answer in the moment.

Okay, so your choices were a, eukaryota, b, bacteria, c, archaea.

The answer is eukaryota.

Okay, so let's have a go at some practise questions.

So what we'll let you do, so read through those, answer the questions.

So pause the video, answer the questions.

I'll go through the answers in a moment or two.

Okay, so filling the gaps, using the following words, eukaryota, bacteria and archaea.

So a, which contains four kingdoms? Answer being eukaryotes.

Which are primitive bacteria that live in extreme environments? That's the archaea.

Part c, which two words contain one kingdom? Answer is the archaea and the bacteria.

Extremophiles are bacteria.

Plants and animals are eukaryotes.

Yeast and protists are eukaryotes.

And e.

coli are bacteria.

Okay, so let's summarise the lesson, our classification into kingdoms and domains.

So we've learned today that Linnaeus classified organisms based on their physical appearances, their phenotypes.

And from this, he proposed letters of classification of kingdom, phylum, class, order, family, genus, species.

He introduced the binomial naming system which gave each organism a two-part name, the first part being genus, the second part being species name.

Later using more modern techniques such as DNA sequencing, Woese developed the use of comparing similarities and differences in DNA sequences to refine classification.

And from his work he introduced this three-domain system.

There are domains of eukaryotes, animals, plants fungi, protists, bacteria, and archaea.

Now bacteria and archaea are both prokaryotes, that means they are bacteria.

So hopefully, you've enjoyed the lesson and I'll see you bit soon, bye.