The Science of Everything Podcast - Episode 69: Animal Diversity Part 1

Episode Date: December 29, 2014

In this episode we explore the diversity of the animal kingdom. I first discuss the history of taxonomy and give an overview of some key concepts such as morphological similarity, phylogenetic analysis, systematics, cladistics, binomial classification, and the taxonomic hierarchy. Then follows an explanation of the diversity of and relationships between the major animal phyla, including arthropods, echinoderms, molluscs, and many others, with special emphasis is given to the classes and orders in the phylum of chordata (vertebrates).

you're listening to The Science of Everything podcast episode 69, animal diversity, and I'm your host, James Fodor. In this episode, I'm going to discuss the diversity and biological taxa found in the kingdom of animalia or animals. The goal here is to give sense of the diversity of the animal kingdom and the relationships between different types of animals. Obviously, I'm not expecting people to remember even a small fraction of all of the different. obviously I'm not expecting people to remember even a small fraction of all the different types of animals that I'm going to specify, but I'm just hoping that in this episode you'll get a sense of the rich diversity of the animal kingdom, and broadly speaking, you'll pick up some ideas of what different types of animals there are and how they relate

to each other, which is often something that many people, myself included, don't necessarily know very much about. So in this episode, I'm going to talk about basically all of the types of animals that are not mammals. So this includes all of the various phyla outside of chordates, arthropods, mollusks, echinoderms, etc. And also most of the different classes within the chordate order, including the bony fish and jawless fish and birds and reptiles and amphibians and so on. And for the next episode, I'll save talking about the mammalian class,

which obviously is where humans and most of the animals that we sort of are familiar with fit in. I'll leave them to their own episode. Also, I must apologize if you hear additional extraneous background noise in this episode, because I'm actually recording this and these two episodes outside. I'm sort of on holiday at the moment, but dedicated as I am to you, my loyal listeners, I'm making sure to take the time to record these two episodes, get them out as soon as I can. I will let it out as much of the noise as I can, but if there's a little bit of wind or people talking or whatever, then, you know, just sort of go with it. There's not a whole lot I can do about it.

So, that's it. Let's jump in and get started. First of all, I'll talk a little bit about what taxonomy is. So taxonomy is just the science of defining different groups of biological organisms on the basis of some certain characteristics and shared characteristics and then giving names to those groups. So in taxonomy, we group together organisms into basically groups or collections that we call taxa. the singular is taxon and we also give them

each of those taxonomic rank so groups of a given rank are then aggregated to form bigger groups and therefore you form a what's called a taxonomic hierarchy so Swedish botanist Carleneas is credited as being the father of taxonomies he was in the 18th century one of the really the first to develop a systematic

fairly comprehensive at least for the time categorization of organisms and he also introduced the what's called the binomial nominal nomenical for naming organisms where you give the genus and then the species in a sort of a Latinized name. So, for example, homo sapiens, human beings, that the homo refers to the genus, homo, and sapiens to our species. And so all organisms that are given a name, named according to this binomial nomenclature, which gives the species and the genus and then the species names.

And the idea of the Linaean system is that every species gets a unique name, so that it can be identified specifically and uniquely, and also that every species is given a unique classification. So it is put in the taxonomic hierarchy in a certain position in accordance with its characteristics. And that name and position uniquely defines that species, and that's how you know what you're talking about. So the lanane system is sort of the classical system for categorizing species. As I'll explain in a moment, there are other systems as well,

which have to various extents revised and or replaced the lanine system. But the lanane system is really the only one that's sort of widely accepted and still sort of used, sort of generally accepted, although everyone also generally accepts that there are a lot of limitations to it. But that's the one I'm going to mostly be working with here because I think it's the most suited to the type of analysis that I want to do in this episode, just to get a feel for the different diversity in the animal kingdom without necessarily being too worried about evolutionary relationships,

which many of the newer types of taxonomic systems pay more attention to than Linnaeus. Obviously, Linnaeus didn't know about evolution because that wasn't developed until later on. So, let's talk about the different ranks in the system of taxonomic ranks. You may have heard of some of these before. There are actually an indeterminate number of ranks, so biologists can just make up new ranks whenever they like if they feel that the existing ones don't fit. But the main sort of traditional ones are beginning at the top is kingdoms,

then below that you have phyla, and then classes, then orders, then families, and then genre or genus, the singular, and then at the bottom you have species. So species is usually the sort of main unit that we talk about. We talk about different species or discovering a new species. We often think of animals and sort of divided up into species as the most sort of fundamental unit, kind of like individuals or maybe chemical elements, the bread and butter of chemistry. In biology, it's sort of species, at least that's a traditional idea. And I won't talk in

detail about the concept of what constitutes the species, because it's the whole episode in and of itself, and it's actually quite a problematic, difficult concept to define. But Here we'll just accept it and move on because we've got other things to look at. So there's no real definitions as to what is the difference between an order and a family or a class or whatever. They're just different levels in the system, and there's no sort of meaning to them other than the higher up you go, the more organisms fit under the umbrella. Usually also the evolutionarily older it is. So phyler appeared relatively early on, and then within those phyla particular classes that we know today are evolutionarily newer,

basically that's how it's tended to work because over time, the evolutionary time, the richness of the animal kingdom has tended to increase through diversion evolution and as a result we need sort of to develop a richer and richer classification to account for all of those and that's why higher levels of higher tax that tend to be

evolutionarily older. But we're not too worried about that. Just bear in mind that those levels the way I remember it is to use a mnemonic kings play cards over family gravestones. So that's kingdom Fyler, class, order, genus species. Helps you remember the order that they go in from biggest to the smallest.

A few words on some of the more modern attempts at taxonomy or ways of doing that that have, to varying degrees, replaced sort of classical Linaian taxonomy, which was based mostly on shared characteristics. You look at particular morphological characteristics of what the animals look like and how they behave and their limb structure and symmetries and development cycles and other things like that. and you classify them on those bases. That's the sort of traditional system.

That's what Linnaeus did, more or less. These days, there are other ways of doing it. In particular, one field of study called phylogenetics is the study of the evolutionary relationships between groups of organisms, which is done through molecular sequencing and looking at basically genetic genomic data to see how the mutations developed over evolutionary time

in it, and using that sort of data-driven genetics, approach to determine the relationships between animals. So it's not based on morphology, it's based on genetics, which is quite a different approach. You sometimes get similar answers, but often you get quite different answers because of phenomena like convergent evolution, for example, where you have different species in similar environments, which, although they are evolutionarily distinct, so they don't evolve from a common ancestor, but they develop similar characteristics because the environments that they are in similar.

That's just one of many ways that you can have similar morphology, even though you have different genetic. There's a related concept or approach which is called cladistics, and this is an approach to biological classification in which organisms are grouped together based on whether or not they have a shared characteristic with a unique last common ancestor. And so basically, cladistics works in a very different way. It doesn't have ranks or taxa like you do in the Linnaean system.

Rather, what you do is that you just keep looking for last common ancestor. So you might look at, for example, humans and chimpanzees and you look for when they branched off the last common ancestor of those, and then you mark that as a breaking point, and then you look further back, okay, when did that species that diverge to become chimpanzees and humans, when did that have a last common ancestor with, say, gorillas?

And then when you find that, you go back and further and further and further, and you just go sort of further back in evolutionary history looking for more and more last common ancestors with bigger and bigger groups of animals, so the last common ancestor of reptiles and mammals or the last common ancestor of vertebrates and invertebrates and so on. So there's no sense of a hierarchy or levels or anything like that. It's just looking at an evolutionary tree, basically.

So cladistics is much more sort of true to the evolutionary history, but it's also much messier because it's much harder to make comparisons. You can't say that there are two things in the same phyla, because you don't have a concept of phylaher, really, in cladistics. You just have what are called clades. A clade is a group of animals or group of species that includes everything, that comes from every descendant of a given common ancestor and only descendants of that common ancestor. I'll talk a little bit later about some of the issues with that because...

So it turns out that many of the traditional taxer in the Linnaean system are not actually clades. That is, they include multiple lines, evolutionary branches sort of thrown together, or they only include some things and not other things from an evolutionary branch. And a lot of biologists think that that's a bad way of doing classification. you should have either all or none of the descendants, basically. But that's something I'll talk a little bit more about later. Just a few other concepts and ideas and words that I wanted to define. So phylogeny is the evolutionary history of a species or a group of species,

and systematics is the study of biological diversity, particularly over time. So phylogeny and systematics are kind of quite similar. It's just phylogeny more refers to the evolutionary history in particular. So it's the history. you talk about the phylogeny of this species, it's its evolutionary history, its development over evolutionary time, and systematic is sort of the study of the evolutionary history of particularly many species. So they're similar but related concepts, phylogeny and systematics.

And so it's from those type of words that we get terms like phylogenetics, for example, which I mentioned earlier, it's using genetics approach, so hence the genetics part, to study phylogeny, the evolutionary history species, so hence we have phylogenetics. At this point, I think I might just introduce, the type of analysis I'm going to be doing and also explain an important concept by mentioning one of the biggest distinctions of animals that you've probably heard of before, the difference between vertebrates and invertebrates. The basic idea here is that a vertebrate is a type of animal that has a backbone or that has vertebra.

Humans are vertebrates because we have a back. All mammals and reptiles and many fish and all birds, they're all vertebrates. Now it turns out that vertebrates form what is called a clade. So all vertebrates share a unique single common ancestor, common ancestor, which goes back hundreds of millions of years ago in evolutionary time. All vertebrates are in a phylum called chordates or cordata, which includes all of the vertebrates, plus a few other things, which are kind of close to vertebrates. Vertebrates are a traditional Linnaean taxa, which corresponds to a clade.

Obviously, Linnaeus didn't know this. He based it on the morphological similarity of having vertebra. But it turns out that that corresponds to the evolutionary similarity of being descended from a single common ancestor. So in that case we have taxa is a clade. And so that one's all good. There's no real controversy about whether that's sort of a valid classification. But if we then talk about invertebrates, that's a different matter,

because invertebrates is an example of what we call a waste basket taxon, or a dustbin taxon or catch-all taxon. There's a few different names. Basically, it's a term used to refer to a group of organisms or species, which have just been sort of thrown together in some classification, because they don't really fit anywhere else. and often these sort of wastebasket taxa, for example in the case of invertebrates, are what we call polyphylic. I think that's how you pronounce it, maybe it's polyphilic, but what it means is that it does not constitute a clade.

It actually has multiple clades in it. So invertebrates do not share a common ancestor, or actually a more careful way of saying that they do share a single common ancestor, but then they also share a common ancestor with vertebrates. So there's no way of classifying the category of invertebrates that I'm. without either including vertebrates, or bunching together a bunch of different clades which do not descend from a single common ancestor. As you'll see, the classification of invertebrates, which actually isn't in the Lanay and high, I'm just using it as an example, the classification invertebrates actually includes

a very large number of different phyla, which do not share a unique common ancestor distinct from chordates. So there are actually many examples of these polyphylic or wastebasket taxa found in in the traditional lanaiet system. Antelope is another example. It turns out that antelope actually doesn't refer to any specific or group or meaningful clade. Really, it just refers to any species within the family of Bovidae, which is not either cattle, sheep, water buffalo, bea, or goats.

So it's just anything else that was left over from those. So that, again, they clearly don't share a common ancestor, distinct from cattle and sheep and so on. Protists is another example of, in this case a whole kingdom, which is sort of a waste market, a waste basket, excuse me. If you've heard of protests, then you'll know what that means, otherwise, don't worry about it, because we're not going to focus on them. We're here to talk about animals.

So, let's move on from talking about taxonomy to talking a little bit about the concept of kingdoms. Lonegas only had two kingdoms. Remember, kingdoms is sort of the highest level of the taxonomic hierarchy. There's kind of another level above that called domain, but I don't want to get into that too much here. Linnaeus proposed basically animals and plants, and that seems fairly common sense. There's obviously a big difference between those.

Basically, later on, people added protists, which are essentially microscopic organisms, which Linnaeus didn't really know much about. And Linnaeus, as a... Sorry, a protest, as I mentioned just before, are sort of a grab-bag category. It's everything that's not an animal or a plant. Later on, fungi were actually split off from protests and given their own group, given their own kingdom, I should say. And we also learnt about bacteria, or prokaryates, which were then split off into their own kingdom and then later on became two domains, but we're not too worried about those.

All of the other kingdoms that I mentioned, that is animals, plants, fungi, and protists, all of those are what we call eukaryotes, which means they have a cell nucleus and other internal organelles. I think I mentioned some of these in previous episodes about the cell. So today, within the eukaryotes, we have four kingdoms, generally recognized, as I said, animals, plants, fungi, and protists. The distinction between those is essentially that plants, photos, and pesticides. synthesize, so they make their own food. Animals eat either plants or other animals. Fungi

eat dead and decaying things, and protists are small microscopic organisms that don't fit in any of the other categories. So that's one of the examples of a wastebasket taxa. I think that animals and plants and fungi are clades, but protest are definitely not a clade because they're just a grab bag of different things. So what we're looking at in this episode is just the animal kingdom. So we're not looking at plants or fungi or protists. There is, it's actually quite difficult sometimes to decide whether something should be a protest or an animal, because some of them are quite similar. Many animals, as it turns out, are also microscopic or near-microscopic, but anyway.

Oh, I should also point out one thing, that if you consult different books, you will see slightly different categorization systems, because there is no single universally accepted one. The one that I'm presenting is sort of fairly classical, fairly standard one, but you will see differences. So don't worry too much about that. I'm just focusing on the broad brushstrokes of how the different things are related, how different types of animals are related to each other and the sort of diversity that exists,

not all the details of exactly what fits in where. It turns out that if you dig into this, there's a lot of controversy, particularly because the influence of genetics and phylogenetics and clodistics and so on, a lot of previously held views about the relationships and proper classification of different animals has been thrown into debate, so so many different areas you look them up, and it's like this taxonomy is subject to dispute, and there's disagreement and different models that have been proposed, so I'm giving a fairly classical view. there are certainly lots of different views.

I'm not saying this is the correct categorization. I'm actually dubious that there is a single correct one. It's basically just a way that we can view the world and understand it. That's all I'm trying to present here. Okay, that caveat being made, let's start talking about the animal kingdom. So if you remember below kingdom, the next level in the Lenane hierarchy is called phyla. Well, phylum is the singular. Now, the traditional classification system for animals has 35 different phyla.

if you recall, core data or chordates, basically vertebrates, is just one of those. So pretty much all of the animals that you find in, say, zoos or on farms, most of the things that we think of as animals are in just one of those 35 filer. Now, I'm only going to talk about a dozen of them, because most of them, about 22 of them, only have a few hundred species in them. Some of them only have one or two species that have been found. And most of these 22 that I'm not going to talk about are just different types of worms, so they're kind of not that interesting.

So we're not going to worry about all those different types of worms, although we will talk about some types of worms. Now, I'll go through the different phyla in order of their size, size being measured by number of species. And I'll just make a clarification here that when I talk about the number of species in different at different taxonomical levels throughout this series of podcasts, I'm referring to the, I'm always referring to the number of described species. So not the total number of estimated species, but the total number of species that

been scientifically described. Also, I'm only talking about extant species, which means species that still exist and live today, as opposed to extinct species. So I'm not talking, I don't include any extinct species, just extant ones that have been described. That being said, which phyla has the most different species in it? It turns out that that's the arthropods, with over 1,000, 1.15 million, according to my figure, a different species. Arthropods includes basically insects and bugs and spiders, all those sorts of things. But far and away, that has more species than any other of the phylar. The next one down, which is mollusks, which is like clams and things like that, only has about 80,000, 90,000 species. So you see the huge difference there, 1.1, 1.2

million to 80,000. Arthropods is just far and away the most diverse animal phyla. Then are the chordates, we've heard about them. They're the vertebrates, lizards and mammals and all that stuff. Also many types of fish, about 60,000 species. And then the, sort of the next three, in terms of level of diversity, roughly, are different types of worms. So these are flat worms, nematodes, which are round worms, and anilids, which are segmented worms. And they each have, you know, 20 or 30,000 species in them. So there's quite a few different types of worms. Remember, there's also those 22 additional phylaid that I'm not really going to talk about, each of which has a few hundred, maybe a thousand species in it. Most of those file are also different other types of worms,

but sort of less common ones. The round worms, the flat worms, and the segmented worms. Next down are the echinoderms. This is basically things like starfish. About 6,000 different species of those. I think all of those live in the ocean. And then the final section that I have on my list of phyla are six phyla, all of which are different types of sea creatures, many of which you probably haven't heard of before or don't know very well.

And these five different phyla are, in order of the diversity. Each of them has a few thousand species in it. Nadarians, Periphera, biroza, rotifera, nematia, and tardigrader. Now, I may have mispronounced some of those. Don't worry about the names. I don't really care about the names. The point is that there are six phyla,

phyla's pretty high level, of different types of creatures, which most of, I think all of these live in the ocean, and many of these are actually microscopic, and they're kind of not things, animals you would have heard of much about before. I will talk a little bit more about them. In due course, I'm just giving the overview of the different phyla.

So the way I sort of remember this in my head is that they're the arthropods, which has almost all of the species in it, over a million. Then there's mollusks, and then there's echinoderms, both of which mostly live in the ocean, mollusk and echinoderms. Then there's all of the different types of worms, three filer of worms, segmented, round, flat. Then there's those six sort of bigger filer of ocean, small ocean-dwelling organisms,

sea creatures I broadly think of them as. And then lastly, there are the chordates. And the chordates are mostly what we think of as animals. We don't tend to think of starfish or things like that as being animals, nor do we think of spiders or bugs as being insects as being animals usually, although technically they are. And those are, of course, arthropods. So most of the things that we think of as being animals

are actually only in one phyla, that is the chordates. And there are, as I said, about 35 other phyler, maybe a dozen of which have a significant number of species in them. So let's look at each of those phyla, the main ones that I mentioned, in a bit more detail, and I'll go through the main classes in those phyla. Remember, classes, the next level down below filer. So, kingdom phylum class. We're going to be looking at key classes now. I'll start with the sea creatures. I won't dwell on these too much, but I'll just give you a feel.

Remember those six phyler of sea creatures that I mentioned? So first of all, the petiphora. There's about 9,000 species of these. These are sponges. So you've probably seen ocean sponges before. You may not have realized they are animals, but they are. They eat other organisms. They don't photosynthesize, so they're not plants and they're not fungi. They are animals. They are motile, that is they move at a certain stage in their development. I don't know the details of that. That's a point about animals, by the way. One thing that animals have in common is that all animals move, so they're motile, at some stage in their development. Some later move into a cessile stage, like sponges, for example, where they don't move, they stay fixed, but at some

stage in their development, all animals move. Animals are also all heterotrophes, which means they don't make their own food. They eat, consume organic molecules from other sources of from existing organisms, either other animals or plants or fungi. So periphery, the sponges. About 9,000 species of sponges. There are three main classes, although most of them fit within one species, are basically the difference between these classes, and I won't bother saying their names because they're unpronounceable,

just depends on the morphology of what they look like. So one of them have sort of spinnacles coming out of them, which are made of calcium carbonate. So they look kind of spiky. Another type is more cup shape. So there's a few sort of main classes of periphery, the sponges, but they fit in their own phyla, and they are animals, which you may not have known. Now, next one, which has 4,000 species, so a bit less than the sponges, is the Briozoa,

which are moss animals. So they kind of look like moss, but they are actually animals. And again, there's three main classes of these, sort of distinguish between whether they're marine or freshwater, and some other distinctions between them. We won't worry too much about those different classes. The Naderians, about 10,000 species of these. these include the corals, jellyfish and hydra.

So you might not realize that coral and jellyfish are sort of closely related, or at least sort of reasonably closely related. Naively, you might have also thought to put sponges and corals together because they're kind of both sort of sessar, right? They don't move. So there are four main classes here, and it's quite interesting. You might not have predicted how they do it.

So one class called the Anzazzoa, and I must forgive my pronunciation here, because I'm going to get so many of these wrong. Normally I would look up how to pronounce these words correctly, but in this episode there are just going to be so many that it would take way too long to do that. So there's going to be a lot of mispronunciation, so forgive me people who work in these fields

and actually can pronounce these words properly. So the anthozoa, these are the anemones. You may know about those sort of tentacle-like plant things that live on the ocean floor, featured prominently in the film Finding Nemo, and also some other coral reef sort of plant-like things, about 6,000 species of those. So that's one filer.

And then there are two jellyfish filer, the box jellyfish, and then the true jellyfish. And then the last filer, which is called the 100, Hydrozoa, these are sort of small predatory animals which include freshwater jellies, which are kind of like jellyfish, but not exactly like jellyfish, and also things called polyps and air ferns. So a key point there is that there are actually two distinct phyla of jellyfish, the box and the true, and then there's some other things that are kind of like jellyfish, but not exactly

jellyfish, which go into Hydrozoa, and then the sea anemonees and other coral reefs sort of stuff, which fits in the fourth phylael. Sorry, the fourth class, excuse me, all within the Darien phylum. Moving on from them to the rotifers, rotifera, about 2,000 species in this phyla. The name literally means wheeled animals, because they kind of look like that they have wheels. They're very small water-dwelling creatures.

There's three main classes of these. Most of the 2,000 species, though, fit into one class called the monogonum, monogonototau. I don't know how to pronounce that. They're quite interesting. I've heard of them a few times, but I don't know very much about them. They're just small, water-dwelling creatures.

Look them up, they look kind of cool. Next phyla, nematia, nematia, about a thousand species. This means ribbon worms. So these are another type of worms. About half of them, there are two main classes, half of them basically divide up according to whether they have sort of spines running along them. I was going to say they're backs, but they don't really have backs, but anyway.

So that's an example of a clear morphological difference that was employed to make the distinction here between whether it fits into one class or the other. Does it have spines? Does it have spines? That's a good example of how these sorts of determinations. made. Final one of these sea creature phyla, Tardi Grada, Tardy Grada, about a thousand species in this. These are, again, microscopic water-dwelling animals, which kind of look a little bit like spiders, because they have eight legs, but they're not. They're not arthropods. They're actually in a

completely different phyla, and there's two main classes of these. So, just some highlights of the sea creatures, because I won't really mention these again, because, again, not many of these things people would think of as animals, but in fact they all are animals. We had the sponges in their own philer. We had moss animals, which kind of look like moss, but are not, in another philer. Then we had the nadarians, which includes coral and jellyfish and hydra. And then we also had the rotifers, the wheel animals, and ribbon worms, and then the last one, the Tardigrata, which was a small, microscopic water-dwelling animals that look kind of like spiders, but aren't spiders. All of these things are animals. Let's now move on to talking about the

three different types of worms that I mentioned before, the three different phyla, the flatworms, the nematodes, which are round worms, and then the anilids, which are segmented worms, so-called because they have different segments in their bodies. So if you dig up worms in the garden, I think many of those you find will be segmented worms, because you'll see the body segments that they have. Flatworms are evolutionarily older. There's about 30,000 different species of flat worms, so-called because their bodies are flat. There are four main classes in that philer.

Many of them fit into one class, Trematoda, which has about 20,000 species. These include fluke worms, which are parasites of mollusks and vertebrates. So you might have heard of those people and animals can be infected with fluke worms. In fact, two of the other classes within their flatworms philers are also parasitic flatworms, which some of them live in fish and some of them in their digestive tracts of vertebrates, so nasty things. There's one philer, excuse me, one class within this filer, which is just comprised of all the non-parasitic flatworms. So there's sort of three classes of parasitic ones,

and one class that has all the non-paracetic ones in it. won't bore you with the names, but there's sort of a thousand or a few thousand species in each of those classes. Okay, those are the flatworms, many of them parasites, not too nice. Let's talk about the nematodes, the round worms. There's not much to say about them. There's about 25,000 different species, so similar in diversity to the flat worms. They have tubular digestive systems, they're evolutionarily a bit more recent than the flat worms. You also notice that there's quite a bit more diversity here than was the case in the different sea creatures

that I mentioned before, most of which only had a few thousand different species. These each have a few tens of thousands. Last phylaid, the anilids, the segmented worms that I mentioned. Mostly these fall into two classes. The two main classes in this phythum are called oligokete and polykeet, or keter, each of which have a few thousand species in them. And basically this just depends on whether they have kete or kites, or I'm not quite sure how one pronounces this, which is basically sort of like bristles or spines that are found on the different segments.

Again, a morphological distinction that was the basis of this classification here. So, anilids are many garden worms fit into this phyla here. So that's our three filer of worms. Now let's look at echinoderms, 6,000 species. Now I think most, if not all, echinoderms live in the ocean. These include starfish and sea urchins, are the main types of animals here that you probably would have heard of before. There are six main classes of echinoderms.

One of the classes are the sea cucumbers, about a thousand different species here. You might have heard of these before. They're basically marine animals that have leathery skin and an elongated body. I think they're mostly sessile. They look basically like cucumbers, hence their name. So they form a class, about a thousand different species of those. Another class, about 700 species of the sea urchins, which you've probably heard of before.

They're small, spiny, globular animals. So they're also a kynoderms. There's also a class called the sea daisies, which kind of look like starfish, but they're sort of circular. There's only three species of those, and this illustrates a point that I should mention. The main classification is often very tricky because it's hard to decide what level you should put things at. So clearly, sea daisies are not nearly as diverse as, say, see, cucumbers, three versus over a thousand different types of species, and yet they're both given the same tax level in the taxonomic hierarchy of class. Should sea daisies fit underneath some other class, or should they be their own filer?

it's often very difficult to make that determination, which is sort of why the Linnaean system is kind of arbitrary and a bit subjective about how you decide where to cut off. And there's often disputes about whether something should be. I've heard of cases where some things have been, some groups of species have been, some people have put them as high up as a separate phyla, which you remember is the second highest.

Some people will put them all the way down as, I think, a family, which is one of the lowest. So it's quite difficult to decide this. Also, another point, that often the sort of naive way that we would classify things based on just a layman's looking at something without even looking at, never mind evolutionary relationships, I just mean comparing a layman's looking at an animal versus a taxonomist or a biologist looking in detail at its development and its morphology and other characteristics that it has, how you might come to quite different classifications. So, for example, if I just looked at a sea cucumber, I might think, well, that looks quite a bit like maybe an anemone or maybe

it goes with the sponges or the moss animals or the, or something like that. But in fact, you recall those are completely different phyla, then they're not grouped with that at all. They're actually, those are actually their own philer. These are, these, uh, c-cumas come under echinoderms. So that's what I think can be quite useful at, at understanding, having some understanding of the, the taxonomical hierarchy, is sort of having a sense of where these different types of animals fit together

and what's more closely related to what and more similar to what in terms of their morphology and to an extent their evolution. So that finished that, aside. So I've discussed the sea urchins and the sea cucumbers, two classes of their own, and also the sea daisies, their own small class. There are also starfish, which of course everyone knows, about 2,000 different species of starfish. Also, 2,000 species of starfish. That's so many. Who would have thought that there were that many different types of starfish? There are also a different class called brittle stars. Now these look like starfish, but they're found in deeper waters,

and they're sort of long and slender. They have sort of whip-like arms, which they use for locomotion. They look kind of scary. They look like, sort of like a cross between a spider, and starfish. It's kind of weird. You might want to look them up. I don't know why they're so much less well-known than starfish, because they're almost the same number of species of them, 2,000 starfish and 1,500 brittle stars. Anyway, last one is a class of marine animals called crinodea. Kronodea, I'm not quite sure how to pronounce that.

About 500 species. These are also marine animals that look kind of like plants, but they have a mouth and feeding arms. And so they can live on the ocean floor or as free swimmers. I think the idea is they sort of brush food into their mouth. So they're kind of like plants that can move around in a sense. Of course, they don't photosynthesize, but they look a bit like plants that can move around. So interesting, some interesting different types of animals in the echinoderms. So echinoderms are types of animals that people don't think about a lot.

Probably the only one people have heard of are the starfish, and the sea urchins, the two main ones. People might naively describe those as fish. Well, fish isn't really a well-defined taxa, but they're certainly not very closely related at all to most of the things like salmon or tuna or whatever that we would ordinarily call fish, because those are vertebrates, whereas these are echinerms. So completely different phyla.

Or to put it differently, a sea urchin is more different from a fish than you are different to a lizard. Anyway, let's move on from echinoderms and talk a bit about mollusks, which is the next phylum, which has about 85,000 different species. They're actually the second biggest filer below, of course, arthropods, which I'm coming to. Mollocks also, like echinoderms, I think, mostly all exclusively live in the ocean. Life, of course, first developed in the oceans, and so that's why most phyla are found in the

oceans. So mollusks include things like snails, oysters, cephalopods, and some worms. So there's, I think, about eight classes of, main classes of mollusks that I have listed here. So a couple of them are just sort of worm-like organisms with a few hundred species in them. I'm not going to worry about those too much. Again, to illustrate at another point that I've mentioned worm-like organisms a number of times. Some of them have their own phyla. Others fit into under mollusks or there are also some arthropods that look a little bit like worms. So again, things that we might naively classify as being, oh, well, they just look like worms can actually be sort of quite distinct from each other biologically. Anyway, so there are some mollusks that are basically looked just like worms.

I'm not terribly interested in those. Most, the single largest class of mollusks, remember, of 85,000 species, 70,000 of those, roughly, are gastropods. You may have heard of that. These are all of the snails and slugs that live in the ocean, fresh water, and on land. So, snails and slugs are types of mollusks, and they have their own class, the gastropods. The second biggest class within mollusks are the bivalvia, which, and there's about 20,000 different species of those. These are clams, oysters, scallops, and mussels. They live in the ocean and freshwater, and so you've probably heard of those bivalvia because essentially they have two halves to them. Then there are two other main

classes of mollusks. There's one called polyplacopororor. I'm not quite sure how to pronounce that. These are chitans. They live in rocky sort of tidal areas on the seabed. They kind of look like a plant or a fungus, really. But they're actually an animal. They're actually a mollusks. Quite old evolutionarily, I believe.

Oh, sorry, there's an extra one. Tusc shells, which live in the ocean. They would kind of look like clams, but they're actually their own class. The final one, though, about a thousand different species, are the cephalopods. Now, the cephalopods include squid, octopus, cuttlefish, and nautilus, they all live in the ocean, so those are animals you've probably heard of. You might not have realised that they were actually closely related to, or sort of closely related,

at least in the same phyla, to clams, oysters, and snails and slug. But not so closely related to, say, sea urchins or starfish, which are in a different phyla, those are a chyneurne. So interesting fact, cephalopods probably are my favourite class of animals because octopuses are actually my favourite type of animal. I might do a whole episode on octopuses at some point in the future, which I don't know if other people find interesting, but I think they're very cool. Animals are very clever. Probably the cleverest of all the invertebrates, although it's hard to measure. Okay, so we've finished mollusks, and with that we've actually done almost all of the animal filer. You recall that there are roughly 35th of an animal philer,

about a dozen of them we're talking about in some detail, about six of them are different types of sea creatures, three of them are different types of worms, and then we looked at the mollusks and the echinoderms. Echinoderms have sea urchins, starfish, sea cucumbers, and mollusks have your, well, a few worms, but also clams, oysters, octopal squid, and all snails and slugs.

So there are only two different phyla left, and these two phyla have basically all of the animals you've ever heard of. Because of all of those phythered before, probably only starfish and snails and slugs and octopause and a few other that you've ever heard of before. All the rest fit into just two phyla, and in fact, almost all of the species also fit into these two phyla because arthropods just have so many different species. Also, chordates have quite a few as well. So those are the two that are left, arthropods and chordates.

I'll talk about arthropods first, because I'm going to go into more detail in chordates than I did in the others because so many of the animals that we know of are actually chordates. So first of all, though, let's talk about arthropods. Over one million different species of arthropods that have been described, many that haven't been described. A couple of, I think, four main subfilis, so subfilter is a taxa that we haven't talked about before that, a level of classification that we haven't talked about before.

It fits in between phylum and class, as you might have imagined. So the four main different types of subfilar, basically they divide up into insects, which is the main one. There are over a million different types of insects, so most arthropods are insects. But they are one subphiler. Then there are the centipedes and the millipedes,

which have their own subfilum. And then there are crabs, shrimps, lobsters, and plankton, which have their own subfiler. And the last one, the last subfiler has spiders and scorpions. So when we hear arthropods, I'm not sure what you think about.

I tend to think of spiders, but actually that's only one subfiler within arthropods. So I'll talk about that one first. There are about 77,000 different species in this subfiler, and I won't even try and pronounce the name. One of the classes in the subfiler, which has almost all the species, about 75,000 species, are the arachnids. So arachnids is a class inside the phyla of arthropods. And this includes spiders, scorpions, ticks, mites, and all of those sort of nasty things.

The other class are sea spiders. So, I mean, basically spiders that live in the sea. There's about a thousand species of those. They have their own class. Some people might be interested in arachnids a bit more, but I kind of don't like spiders, so I didn't go into too much detail about those. But they are a type of arthropod.

Next one, the crustaceans. These are another subphylum within the phylum of arthropods. These are shrimp crabs, lobsters, and plankton. So most of these fit into the class of maxillopods, which are barnacles, basically. Those are the things that live on ships. I was going to say grow on ships. I guess they do grow, but they're not plants. 15,000 of those. Also, 40,000 species, crabs, lobsters, shrimp and krill.

Those are all in a class called Malikos straker, or stracker, which has about 40,000 species, crabs, lobster, shrimp and krill. And then there are two other classes, which are mostly shrimp and other sort of marine plankton. So those are the tiny ocean-dwelling creatures that whales eat. So those are actually crustaceans. Moving on, the third of the subfiler. This one has about 13,000. species, centipedes and millipedes. So essentially within those you have a class of centipedes, a class of millipedes, and two classes of things that are kind of halfway in between centipedes and

millipedes. Those are also arthropods. Arthropods, by the way, I should have mentioned this before, tend to have sort of hard exoskeletons, not exactly shells, but hard external skeletons. So spiders have those, scorpions have those, crabs have those, and millipedes and centipedes have those. So that's one thing that they sort of have in common. So we've accounted for maybe 150, 200,000 species of arthropods, but there's still about a million of them left. And all of these are grouped into the subphiler called hexapods. And these are the insects. The insects are the single, or Insectar is actually the class.

There's another very small class which has a few wingless insects, but we don't care about those. So basically we're looking at a class called Insectar. So the insects. There are a million species of insects, the single largest class in the animal kingdom. indeed there are more insects than all other types of animals put together, and there are many, many different types of insects. I don't even know how many orders I've got listed here, about 20 different orders of insect. I'll just mention a few of them. So one of the largest orders has about 120,000 species.

These are the flies, the mosquitoes, midges, gnats, and the fruit fly. Flies are actually quite interesting because there are things called the true flies, and these are things that are properly called flies. and they're usually referenced by some sort of adjective and then a space, so a separate word, and then the word fly. So one example is fruit fly, that they're a type of true flies. Then there are these other things that are sort of called flies but are not proper flies. An example is a mayfly or a dragonfly, and those are written as a single word. So that can be an interesting way of distinguishing between a true fly and a sort of a quasi-fly,

whether it's written as one word or two words. If it's two words, it's a proper type of fly, and you're just telling what type of fly it is. if it's a single word with fly on the end, then it's not a real fly, it's something that's kind of like a fly in some way. So about 120,000 of types of flies, and who knew, I certainly didn't know this, that mosquitoes were actually technically a type of fly, they're in the same order as the other true flies. And order is pretty low down on the taxonomic hierarchy. So mammals are an order, so mosquitoes are in the same order as fruit flies, kind of closely related, which I wouldn't have expected. Another order that has a lot of species,

in it, about 120,000, are the hymenoptera, and these are ants, wasps, bees, and sawfly. So these are most of the, what are called the U-Ssocial insects. So the insects that have big colonies and work in large groups. In particular, ants and bees

are ones that people are probably quite familiar with. Those are a type of insect. 150,000 different species of ants, wasps, and bees. Incredible, the diversity there. That's more than all of the different types, all of the different species of vertebrates put together, just in ants, ants and bees and wasps alone.

There is an order called hemiptera, or hemiptera. Again, I'm sorry, I don't know how to pronounce this, about 80,000 species in this one. These are bugs. Now, colloquially, we often use bugs to refer to, well, any small crawly thing, pretty much any type of insect, or even perhaps anything in the whole phylo of arthropods,

phylum of arthropods. But actually, there is a specific order of animals, which are the true bugs. and that's this order here, the hemiptera or something, which includes cicadas and aphids and leafhoppers. So these are actually, correctly speaking, bugs. There's an order which has about 20,000 species in it. The grasshoppers, crickets and the locusts,

all, as you might expect, fairly closely related to each other. Another one that has the dragonflies, and there's a such thing called a damsel fly, which I never knew about before. Dragonflies and damsel flies. About 6,000 different species of those. Just amazing the diversity.

But I'm leaving there. there is another order called Lepidoptera, a Lepidoptera, which has about 175,000 different species, butterflies and moths, just butterflies and moths, 175 different thousand different species. And those are just the ones that have been described. There are many more that would not have been described. So just insane the diversity within the class of insects.

But by far, far in a way, the most populous one, is an order called, an order called colioptera, which is the Beatles, not the band. I mean, beetles, the bug, the type of bug, although of course we know they're not true bugs, because that's a different order. But anyway, the type of insect, beetles. There are 400,000 known different types of beetles, and there are, of course, thought to be many more that have not been described in the literature. So, again, this is by far the largest order of animals that exists. There's a joke, and I can't remember who said this. Someone asked him a question, something like, what can we tell about God based on the different types of animals that exist, or,

based on evolution or something like that. I don't know exactly what it was. But anyway, the answer was that we know that God must have an inordinate fondness for beetles, because he just made so many different types of them, 400,000 different species of beetles. There are about as many different species of beetles as there are all other different types of non-insect species. So if you add up all the number of species in echinoderms and the sea creatures that I mentioned and mollusks and cordates, put all those together, you still don't have as many different species as you have just beetles. crazy how many different types of beetles there are. And they fit all in one order within the class of insects.

So there are many other orders in insects as well, a very, very diverse class. I'll just mention many of them are actually different types of lice, which is actually kind of gross. So I'll just mention a few of them. There are biting lice and sucking lice, some of the other different orders. Silverfish have their own order.

You've probably seen those crawling around the house. Mayflies, stone flies, ice bugs. Stick insects, there are about 3,000 different species of stick insects. They have their own order. Web spinners, their own order. Mantises, so the praying mantis, they have their own order. Cockroaches, which I think I mentioned it before, they have their own orders. About 3,400 different species of cockroaches.

Termites, about 3,000 different species of termites. And then there's another one that sort of look like termites. Barklice and book lice, about over 5,000 different species of those. Something called cone heads, catas flies, a bunch of others that I haven't even mentioned. So lots and lots of different types of insects. It's just crazy the diversity of the insect order. So I'm sort of emphasizing that because that's all we really have to say about, well, arthropods, actually.

We're done with arthropods. Obviously, one could do a whole series of podcasts just on the different types of insects and so on. But that's not what we're doing here. Our focus is on animals generally, and more specifically, we're going to dive into chordates and even more particularly mammals, for fairly obvious reasons, I hope. But it's time now to move to the last of our animal phyla, and that is the chordates, or basically vertebrates.

There are about 60,000 different species of vertebrates. Sorry, of chordates. Pretty much everything that we usually think of as animals, as opposed to, like, worms or insects, fits into this phylum. So this is fish, mammals, birds, reptiles. The classification of chordates is kind of complicated because of the different superclasses and subfilums and whatever else. there's just a few that I sort of want to mention before we dig into the main superclass that I'm interested in, which is tetrapods. You've probably heard of tetrapods before.

It means all four-limbed animals are in the same superclass. There are about 30,000 different species of tetrapods, and the four classes there that you will almost certainly have heard of before, amphibians, reptiles, birds, and mammals. But that's to come, because there are actually some other different types of chordates as well. So there's one sub-fileum called tunicates, and there's about 3,000 different species of those. These are underwater filter feeders. So they look a bit like some of the sea creature phyla, like the rotophers,

for example, some of those other things that we discussed earlier. But they're actually chordates, because these ones don't actually have vertebrates, but they have a notacord, which is a developmental feature which invertebrates forms into the spinal column, although in these things, tunicates and others

they don't actually have vertebrates. They don't have vertebrate, but they have a notacord, which is kind of like the stepping stone, to getting a backbone, I guess you could say, putting it loosely. So mainly in this sub-filer of tunicates, there are a few classes of things, as I said, 3,000 species. Basically, these are animals that we would describe as sea squirts or filter feeders. They're kind of a bit like sponges in the way that they just sort of, or some of the other creatures,

and they just sort of eat what comes to them. But they are chordates because they do have no chord, so that they are much more closely related to humans than some of these other sea creatures that they mentioned earlier, even if they look kind of like them, at least it's superficially. But I'm not too interested in those, underwater filter feeders. There's another subphylum, which are the lancelots. There's only 30 species of these, not very many of them left. They're basically flat fish.

They kind of look like eels, but sort of flattened out, and they live in the ocean. They also have no source, but they don't have a proper backbone. So they're sort of like a step on the way towards fully formed vertebrates, if you want to think of it like that. So important to understand evolutionarily, but not very important because there's not very many species of them left. Then there's the Agnathar, about 100 species of jawless fish. This is sort of the most evolutionarily primitive type of fish. It's not really correct to think of evolution as a sort of a stepping stone upwards in this way, but it can be helpful to think of an evolution to think of sort of evolutionary stages of moving from one thing to another.

So if you imagine the sort of canonical story of fishers, fish coming out of the ocean and, you know, forming, legs and then walking on land and then turning into reptiles and then eventually mammals and humans, the stages that they went through, beginning with invertebrates, so things that did not have a backbone. First of all, you had something like the lancelots, which just started to develop a nodocord, so like on the way to the backbone. And then you had jawless fish, which is sort of like a little bit closer to monfish. And then you had cartilaginous fishes. That's another, a sort of a subclass, or sorry, a sub-filthum or superclass in chordates. There's about 900 species of cartilaginous fishes. Sharks are the most well-known type of cartilaginous fishes. That's sort of a step

up above the jawless fish because cartilaginous fishes do have jaws, they have no decoys, but still don't have a proper internal skeleton yet, because they haven't quite got there in terms of the proper vertebrae yet. And then finally, we get to a bony fish, about 30,000 different species of bony fish. These are most of the fish that you sort of think of as, like, proper fish. These are the fish that have, you know, fins and gills, and that sort of trout and salmon and all of that sort of stuff. Those are the bony fish. So evolutionarily, they're sort of like the most closely related to the land vertebrates up from, as I said, the cartilaginus, which in turn is a sort of a step up from the jawless, which in turn is sort of a step up from the lancelets. Quite a lot of species of fish. About half of all chordates are bony fish. There are two types of two classes within the superclass of bony fish.

One of them has essentially all of the species. These are so-called ray-finned fishes. Pretty much all the fish you know about fit into that class. And then there are the lobed finned fishes. These were, I think, thought to be extinct, but there are now known to be eight extant species. In this is the... Actually, there are two species of sealocamp. These are very, very evolutionarily old fish, which still have lobes rather than rays.

And then there is, as I mentioned before, about 30,000, or maybe 28,000 different species of tetrapods, four-limbed animals, including 6,000 species of amphibians, 8,000 species of reptiles, 10,000 species of birds, and a mere 5,500 species of mammals. Hopefully you know what mammals are.

They're basically animals that have fur and that suckle their young, as opposed to reptiles, which are sort of scaly and lay eggs, and amphibians which also lay eggs and kind of live half in and a half out of the water. Of course, you know what birds are. Let me compare, just to give some perspective, let me compare mammals to some other classes, so same level on the hierarchy, in terms of number of species. So, for example, there are about the same number of species.

species of mammals as there are monoganea, or monoganea, which are a type of small parasitic flatworm that are found in the gills of, or skin of fish, and almost certainly you've never heard on before, about the same number of species of those as there are of mammals. There are about 70,000 species of gastropods, as I mentioned before, so many, many times the number of species of mammals, and those are snails and slugs. Many, many times a number of species of snugs as there are a number of species of mammals. Of course, we could look at the insects, grasshoppers, 80,000 species, cockroaches, 3,400 types of species. Remember, 5,500 different types of mammals. 3,000 species of termites, of course, we remember the 400,000 species

of beetles. So just to illustrate the point that the diversity of the animal kingdom is far and a way greater and goes far beyond and outside of what we ordinarily think of as animals and all the type of animals that we are. But anyway, we still are mammals and we still are interested in animals that are kind of like us. So we're going to spend more time on chordates and we'll get to mammals. Before we get there, though, there's a bit more to say about the bony fish. So I mentioned the two different main classes of bony fish, the ray finned and the lobe fined. I'm going to talk briefly about some of the different orders within the rayfinned fishes. Remember that order is the next level down below class. So class is sort of where mammal, mammalia is a class. So mammals

are a class. I'm now going to just briefly go through some of the Rayfinned fish orders. There are dozens of them. About 30,000 species in total. What I'm going to do is I'm just going to mention the name of a fish that you've probably heard of before, or type of fish, actually. Each one of these is a different order of fish. So each of these has about as much diversity as sort of primates, you know, very loosely speaking. So, reed fishes, sturgeons, gars, bowfins, moon eyes, ladyfishes, bonefishes, true eels, gulper eels, herrings, milkfishes, carp, electric eel, catfish, barrel eyes, salmon and trout, that's one,

pike, jelly nose fish, bristlemouth, Bombay duck, Latin fish, ribbon fish, beard fish, cave fish, toad fish, anglerfish, cod, pearlfish, mullet, silver sides, flying fish, whalefish, whalefish, live bearers, ridge, heads, fangtooth, dories, clingfish, stickleback, seahorse, Swampil, flatfish, scorpion fish. Each of those was a different order of fish, and that of course wasn't its proper name. That's its common name. You can hopefully get a sense there of the huge diversity of fish.

But actually, all of those orders only account for about 60% of the roughly 30,000, so maybe something like 20,000 different species of fish. There's about 10,000 species in the order called Perseforms, which is about 40% of all fish, all rafeined bony fish. And this includes many of the fish that you would have heard of before, so things like mackerel and tuna and whiting and things like that. Those are all actually fit in the same order.

I'm not quite sure why that one so much bigger than all the others. But that's another thing that can be useful when studying taxonomy, is to get a sense of sometimes there may be lots of different orders or classes or something like that, but one of them is far and away bigger than all the others, and so you maybe want to focus on that. like, for example, insects is far and away bigger than many of the other different classes. Okay, so that's just a sense of the diversity of fish. We're not going to go into the details of any of those.

It was just to give you a sense, but those are all bony type of fish that have, you know, internal skeleton, backbone and so on. There's also, as I mentioned before, lobed fin fish, which are their own separate class. There are only eight different species of these. There is two species of cilicamp, which are their own order, and then six different species of lungfish. So very evolutionarily ancient type of fish there, but not very many around. So compared to fish, bony fish, amphibians and reptiles actually have much, much less diversity.

There are about 6,000 species of amphibians and 8,000 species of reptiles, so that's several times less than the bony fish. But also the number of orders is much low. There are only three different orders of amphibia and four of reptiles. Amphibia, most amphibia are frogs and toads. That's the order called the Anura, or Anuron, I'm trying to say that. About 5,600 different types of species of frogs and toads. The only other types of amphibia that exist are salamanders and nukes. They have their own order.

500 species of those. And something called the Sicilians, which you may not have heard of before, they basically look like snakes, but they're actually amphibia, not reptiles. Most snakes are reptiles. So in terms of amphibians, most of them are frogs and toads. So there actually isn't that much diversity left of amphibians. as really only what we would call frogs, toads, salamanders, nukes, and a few hundred-and-so species of Sicilians.

In terms of reptiles, there's a bit more diversity, but not too much. Most reptiles, about, in fact, almost all of the species, something like 7,800 or so, are squamata, basically lizards, snakes, and worm lizards. So quite a lot of species are well over 7,000 species of lizards and snakes. That's more than all the species of mammals. They have their own order. Then there are about 300 different species of turtles and tortoises, which have their own order as well.

There are about 23 species of crocodiles and alligators, and a few other things, which have their own order as well. So, again, you see one order which has 23 species, another one which has over 7,000 species. A very big difference there, but both at the sort of same level. It goes further than that, because there's one more order of reptiles, which are the Tuotaras from New Zealand. There are only two different species of these. They basically look like lizards, but they are actually distinct enough. to have their own order. I'm not precisely sure why that is why they're not classed with lizards, but there's something different about them enough to have their own order. So, just going over

amphibia and reptiles again, because many people are a bit less familiar of those than they are with mammals, we had seven order in total, three in the three amphibia, one, frogs and toads, that's most of the amphibians, then there's salamanders and newts, and the Sicilians, which are kind of like snakes. Then in the reptiles, we had most of them being snakes' lizards, and then there's also a few hundred tortoises and turtles, and then the crocodiles and the tuataras. Now, before we move on to birds and mammals, there's something I want to say here about the evolutionary relationship

between these four different types of tetrapods. Remember, tetrapods are reptiles, mammals, amphibians, and birds. All have four main limbs. You might not think of birds as having four limbs, by the way, but they do the wings count. So if we look at the evolutionary history of tetrapods, the amphibians were the first to branch off. They form their own clade.

Remember, that's that they're all descended from a single common ancestor. And then we had mammals branching off, after that. Then next we had turtles and tortoises branch off. Then after that came snakes and lizards branched off. Then the crocodiles branched off. And then finally, the birds branched off, or actually crocodiles and birds branched off from each other. That's evolutionarily the most recent to occur.

Now, the interesting thing is that three of those groups that I mentioned, that is the tortoises, the snakes and lizards, and the crocodiles. Those three we call reptiles. But the other two, the mammals that branched off first and then the birds which branched off last, we call those, well, mammals and birds. In other words, they have their own class. But reptiles, we grouped together three different clades into one class called reptiles. So the point I'm making here is that reptiles is actually, as I mentioned,

as the word I mentioned earlier, a polyphilic classification category on taxa. It includes multiple different clades, or it doesn't include all of the descendants of one common ancestor. One way of fixing this would be just to split off snakes and lizards, tortoises and turtles, and crocodiles, and give them all their own class. But that's kind of an unpopular idea, because there aren't actually that many of each of those. I guess you could kind of do it with snakes and lizards, but crocodiles would be a pretty small class. Same with tortoises and turtles. Another possibility would just be to include birds in with reptiles. that's probably the easiest way of doing it

because if you throw birds in with reptiles then it becomes a clade the trouble is in having them separated out there. It's sort of mammals and birds works but reptiles doesn't because it's just sort of a leftover category, one of those wastebasket taxons that I mentioned earlier. So there's a lot of controversy about what we're going to

do with reptiles exactly because they're sort of not like mammals and birds, they don't fit very well evolutionarily. So basically birds of reptiles evolutionarily speaking deal with it. But according to our classification, they are not. They are their own class, the birds, so it's time to talk about those now, or avies. Aves, it's also, is the proper term. There's about 10,000 different species of birds, so quite a lot. Much, much more diversity than in the amphibians or the reptiles. You remember there are only three or four different orders, but there are, I'm not trying to make, I've got here, 20 or 30 different orders of birds. There's an interesting subclass distinction, so there's one subclass which has almost all the species of birds, like 990,000, excuse me, 9, 9,900. different species of birds. So most modern flying birds fit into this subclass, which is called

New Gnathia or something. And then there's the other subclass, which is paleognathia, so it's sort of an older grouping, which is the flightless birds. And also a small bird from South America, which is called the Tinamu, or the Tinamau or something. The other order, which I won't try and pronounce, are the flightless birds, so Osceizemus, Reyes, and the quay. So they all sort of fit into their own subclass But then in the other one, the Neo-Gnafia, is most modern flying birds. And again, I'm not going to go through all of these individually because there are too many of them, and many of them I don't even know what they are.

You may have recalled before that about 40% of the bony fish just fit into one order, even though there were like 30 different orders, 40% of the species fit into one of them. And I mentioned it was the same thing with birds. So there's one order of birds called Passeraforms, which has about 5,000 different species, which is about half of all of the bird species. And these are pretty much all of the songbirds. So things like crows, ravens, wambles, sparrows, finches, robins, all of the sort of canonical, most bird-like birds in some sense

are actually passiforms. But, as I mentioned, there are many, many other different orders of birds as well, something like about 20. So again, I'll just go through some of the ones you may have heard of. So waterfowls, about 150 species of those. The turkey, chicken, pheasants and grouse, there's about 300 species. They all fit in their own order. Penguins, there's about 20 different species of penguins.

They're their own order. Albatrosses, over 100 different species of those. Well, albatrosses and sort of similar birds. Their own order. Pelicans and other similar, 60 species. Storks and similar, 20 species. Flamingos, six species are flamingos. And again, their own order.

Eagles, hawks, vultures. So these are all the birds of prey. There's over 200 species of those. Falcons, nearly 300 species. also birds of prey cranes, sound grouse, doves and pigeons, they have their own order. Parrots, something like

370 species of those, and cockatoos also fit in there. There's also owls, so the true owls and barn ows, about 200 different species of those. Kingfishers and be eagles, about 90 species of those. Woodpeckers, two cans, barbets and puffbirds, so some of those with really big beaks,

about 400 different species. They're just amazing diversity there. So, that's all we have for today's show. Hopefully you found that interesting. In the next episode, I will move on to discuss the diversity within the class of mammals, and we'll look at up the different orders and families within that. If you'd like to support the show, please jump onto iTunes and give the podcast a favorable review. I always appreciate that, as it helps to raise the visibility of the show.

You can also send me an email. My address is FOD12 at gmail.com. That's FODS12 at gmail.com. Thank you for listening, and I'll talk to you next time.