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Animals, Part II

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Phylum Platyhelminthes 0:04
    • Flatworms
    • Acoelomates
    • Terrestrial, Oceanic, or Aquatic
    • Simple Nervous System
    • Reproduction
  • Phylum Nematoda 4:20
    • Unsegmented Roundworms
    • Pseudocoelomates
    • Terrestrial, Oceanic, or Aquatic
    • Full Digestive Tract
    • Reproduction
    • C. Elegans
  • Phylum Annelida 8:11
    • Segmented Roundworms
    • Terrestrial, Oceanic, or Aquatic
    • Full Digestive Tract
    • Accordion-like Movement
    • Simple Nervous System
    • Sexual Reproduction
    • Class Oligochaeta
    • Class Polychaeta
    • Class Hirudinea
  • Phylum Rotifera 16:11
    • Pseudocoelomates
    • Terrestrial, Aquatic
    • Digestive Tract
  • Phylum Mollusca 18:55
    • Snails, Slugs, Clams, Oysters
    • Terrestrial, Oceanic, or Aquatic
    • Mantle
    • Full Digestive Tract with Specialized Organs
    • Sexual Reproduction
    • Major Classes
  • Phylum Arthropoda 28:16
    • Insects, Arachnids, Crustaceans
    • Terrestrial, Oceanic, or Aquatic
    • Head, Thorax, Abdomen
    • Excretion with Malpighian Tubes
    • Arthropod Groups
  • Phylum Echinodermata 38:32
    • Sea Stars, Sea Urchins, Sand Dollars, Sea Cucumbers
    • Oceanic or Aquatic
    • Water Vascular System
    • Full Digestive Tract
    • Sexual Reproduction
  • Phylum Chordata 42:16
    • All Vertebrates
    • Terrestrial, Oceanic, or Aquatic
    • Main Body Parts
    • Mostly in Subphylum Vertebrata
    • Examples

Transcription: Animals, Part II

Hi, welcome back to, this is the lesson on animals, part 2.0000

If you get to be looking at the different phyla in the animal kingdom, 0006

we pick up on phylum platyhelminthes which literally means flat worms from Latin.0009

The flat worms include planarians which are typically free living flat worms.0015

A lot of them are in the ocean and aquatic environments, some of them in moist terrestrial environments.0021

In flukes in tapeworms, often times tend to be inside of organisms as parasites, these are all acoelomates.0027

If you remember acoelomate means they do not have a coelom, 0034

they do not have that fluid filled cushioning between their outer body wall and the gut internally.0037

And because they are so flat, it makes sense that they do not have that.0042

Terrestrial for a lot of them, you can find them in soils, you can find them in organisms,0047

some are in the ocean, some are in freshwater.0051

Like I mentioned before, free living or parasitic, here is an example of a planarian.0054

That is somewhere around the ocean, here is the head end, here is the back end.0063

They are bilateral, in terms of their symmetry, so you can tell that there is a head end, there is a left and right, there is a back end.0066

There are parasitic ones, as well.0074

The parasitic one here is the tape worm.0077

This tapeworm here, you are looking at segments called proglodids.0080

I am going to tell you more about a proglodid in a second.0089

They have a single opening for their gut, your average planarian, for instance.0093

If you look underneath it, right about here, there is this tube that comes out of what you call the pharynx region.0098

It is like a little mouth tube that they take in nutrients and their waste actually goes out through the same hole.0107

There is just one opening for stuff coming in, stuff going out.0114

In terms of excretion, getting rid of their metabolic waste rather than solid waste, they have these things called flame cells.0119

Actually, you can barely see the extensions of the flame cells here in this tapeworm.0127

They call them flame cells because if you look at the little bulb, if you were to zoom in this,0132

you would see this little bulb area with cilia.0137

The cilia doing this which help get the waste out with water, and it helps them prevent getting waterlog.0141

This build up too much water with waste products inside of it.0151

The flame cells moving with little cilia is what made someone think it looks like a flame.0154

That is how they actually excrete waste, they do not have kidneys.0161

They have a simple nervous system, with ganglia.0165

If you were to look at a simple planarian, there is this little head end, the actual ganglia units,0169

it would look kind of like the rungs of a ladder, the major nerve extensions.0182

The ganglia are these little units extending of it.0192

So that major ganglia, each ganglia up on the head end is the closest they get to having a brain, it is not quite a brain.0198

They do have eye spots, oftentimes, these two little things here, they are light sensitive.0206

They are not seeing actual shapes or colors, they cannot tell that there is light there, there is no light there.0211

In terms of reproduction, how they make babies, hermaphrodites are very common,0217

where the flower actually will have the male and female parts within it.0221

Some have do separate sexes.0226

Regeneration is quite common, for instance, in this proglodid, this right here within the tape worm, that is a single proglodid.0227

You can see the neighboring proglodid there.0237

It is just proglodid after proglodid, next to the head.0239

Within each proglodid, there are male and female parts in there and they can still fertilize. 0243

That allows a tapeworm to re-extend itself, if it gets torn apart, pretty cool adaptation.0253

Phylum nematode, these are roundworms not flat worms, but they are still unsegmented.0261

If you look carefully to their body, you do not see little lines with the segments like you would0267

in the next phylum that I am going to tell you about.0272

These are pseudocoelomates, they have a partial fluid filled cushioning between the outer body wall and their gut.0274

They are terrestrial like this one, this one, that looks like some kind of a cloth.0281

The terrestrial ones often times are in the soil, you also can find them inside of animals, occasionally.0286

Oceanic, there are definitely nematodes in the ocean, in the marine environment, and some fresh water.0294

As I mentioned earlier, some are free living, there are in soils, eating bits of matter in the soil.0301

A lot of times they are good for the soil, their waste that comes out is essentially fertilizer for crops.0307

A lot of them are parasitic, if your dog has worms, typically the worms that you are talking about are nematodes.0314

They expand in the gut area and then their little babies come out the back end.0321

Full digestive tract, two openings, they do have a head end and the back end.0329

The way that you can tell the back end is it is tapered. 0334

The back end where the anus is usually comes to a point, the head end not as much.0341

I will tell you more about this picture in a second.0347

Hydrostatic skeleton, it is allowing their muscles to move properly with respect to how they get around.0350

Its hydrostatic skeleton maintains a certain degree of water pressure that allows them to flush around.0360

If you look at one of these little guys, nematodes, they typically are doing this kind of motions,0368

this thrashing motion and that is how they are motile.0374

Hydrostatic skeleton allows motility.0378

They do not have a real skeleton with real bone, this is the closest they get, in terms of the muscles, 0385

enabling their muscles to move them properly.0391

Their circulation respiration is similar to flat worms, meaning they do not have blood vessels,0394

they do not have true blood flow, or actual hearts.0400

In terms of breathing, it is just through the skin.0405

They do not actually have lungs or gills, they are thin enough where they can have 0408

that respiration through the skin and circulation without a heart or hearts.0412

They do have a simpler nervous system, ganglia similar,0417

just slightly more advance in nematodes compared to the platyhelminthes.0420

Reproduction is typically sexual where they have males and they have females.0425

Males fertilize the females internally, they actually get together and0431

the male inject sperm inside of her and then she lays fertilized eggs.0437

One example of a fascinating nematode is the C. Elegans.0444

The C is short for a very long genus name, this, my friends, is C. Elegans.0448

This was the very first multicellular animal to have its entire genome sequenced.0455

The amazing thing is as an adult, it has less than 1000 cells.0461

In terms of tracing where the specific tissues come from, from that gastrula, that fluid ball of cells, 0465

that is a lot easier to do, in terms of the getting the full complete picture.0473

You can see that this one, so that it can be visualized better has been stained with a fluorescent material.0476

This is under microscope because it is pretty tiny, less than 1000 cells.0482

Its entire genome is the first to be sequenced, and there have been others, of course, after that.0485

Phylum annelida, this is now the more advanced, structurally advanced version of roundworms.0492

They are segmented, examples earthworms, polychaeta, I will show you a picture in a second, and leeches.0500

This of course is your earthworm with its chotelom and there is its little head end.0506

There are coelomates, they do have that fluid filled cushioning to the outer body wall and that inner gut, like us.0513

Terrestrial, you can of course find this in the earth, right in the soil, that is why they are earth worms.0521

Oceanic is where you typically going to find polychaetes.0525

Leeches, a lot of them are actually in aquatic areas, lakes, pond, swamps.0529

Full digestive tract with 2 openings, they have a mouth and they have an anus.0536

Full digestive tract, crop is kind of like a first stomach that holds on the food.0541

Gizzard helps them grind the food a little bit more.0546

The intestine comes after that, the intestine lasts all the way to the end until it gets to the anus.0551

You will see the terms crop and gizzard also be used with respect to birds.0557

But this crop and this gizzard is structurally different.0562

Before the crop, you would actually have this region that you could call the esophagus, like we have.0565

An area called the pharynx like the throat, and then of course starting with the mouth opening.0574

They do have close circulation with hearts, this is the first time we are seeing this with the worms.0579

If you were to zoom into the front part of the body, here is the beginning of the worm,0584

here is that area called the clutton, I will tell you more about in a second, it looks like a band aid.0591

You actually would see blood vessels, a dorsal blood vessel and a ventral blood vessel, at the top and bottom.0596

You would see these loops, they are actually around the esophagus region, 0602

these are called aortic arches, you could call them hearts.0609

They are just very simple hearts, they do not have separated chambers.0613

They are just little beating vessels that circulate blood through blood vessels.0618

Closed circulation means the organism has enclosed blood vessels.0623

They are advantages to doing that, you can get blood to specific regions 0628

pointed to specific regions much quicker and much more efficiently.0633

The biggest organisms on earth have that closed circulation,0636

you can get blood to areas that otherwise, gravity would cause you not to conquer that feet.0639

Closed circulation with hearts, pumping it to specific areas, that happens with earthworms.0647

Move freely in every segment meaning this is a segment of earthworm, these are the segments you would see on the outer body wall.0654

In each one, you have these little groups of cells that act like miniature kidneys, in terms of releasing metabolic waste.0664

And yes, it goes out through the skin.0671

Out of the anus, they only have their solid waste.0673

Typically, if it is an earthworms, it is soil, they eat soil and they get out of it organic nutrients.0676

They have an accordion like movement.0685

They are actually circular muscles that actually encircles the body, and then longitudinal muscles that are kind of like lengthwise.0686

As they do contractions and relaxations, you would see accordion movement, kind of like the accordion instrument.0696

You would see one region get shorter as the other one expands, and that would get shorter, the neighboring ones expand.0703

That allows it to gradually creep through the soil, through the water, if we are talking about a polychaete.0710

Septae are common, if you look very carefully and sometimes you need a microscope, 0716

you would see this tiny little bristles, they are not as easy to see on earthworm.0721

In polychaetes, you would see them much more easily.0728

The other name for these bristles are chaetae but septae is a common term.0732

These septae terminology made of chitin which is a connection to fungi.0740

Fungi have cell walls made of chitin.0748

They a simple nervous system, once again, ganglia, the nerve chord riding on their backside.0751

That particular nerve cord is connected to ganglia up at the front, you see these two little, they have white dots.0766

Now that I think about it, the nerve chord ends up on their dorsal side, underneath these digestive organs.0781

There are nerves extending from there, like little nerve extensions that allows it to feel and move its entire body.0788

The amazing thing is, though their ganglia is right there, you know that is a small brain,0796

right around here, you see these whites sacs that are much larger than the brain, those are their sperm sacs.0802

Their sperm sacs are bigger than their ganglia, which is interesting to think about.0810

More on annelids, sexual production typically occurs.0816

Some can do it sexually, but sometimes you will have the separate sexes, the males and females.0821

When it comes to something like an earthworm, they are hermaphroditic.0827

Both of these earthworms have sperm sacs, vesicles containing sperm.0836

They both have ovaries and they both can receive sperm from each other, they can self fertilize.0841

Each one of them has a clutton, here is the clutton like I mentioned on the previous page.0846

The clutton right here is kind of their mode of getting their reproductive connection happening.0852

They make what it is known as a mucus cocoon.0864

The mucus cocoon allows them to inseminate each other.0872

This one is fertilized and vice versa, they may release a sac of fertilized eggs in the ground,0876

that hatches and gives rise to new earthworms.0882

They are in class oligochaeta, classes are within the phyla, this major class of annelids.0886

They have class polychaeta, this is a polychaete worm.0894

You could see these bristles of septae much more obvious on its body.0898

This is found in the water, moving around, and it is a free living non-parasitic worm, typically.0902

That is a polychaete and they are usually in the ocean.0909

Class hirudinea, this one, this leech is a parasitic, it sucks blood.0912

On its head end, it has suckers, it literally will suck blood out if little capillaries through the skin and through its body.0919

There are benefits to this, I have heard that recently in America, we just have been made legal,0928

once again, for approved to doctor use.0935

Here is one of the way you could use them, besides just sucking poison out of blood, there are other ways to deal with that.0938

But if is someone’s ear gets chopped off and they sew it back on, 0945

and you want to ensure proper blood flow back into the ear, after reattaching it.0949

Put some leeches on here for a short period of time, it helps encourage blood flow back into the ear.0954

You do not necessarily need just to do that, it is just one interesting application where this parasitic worm,0960

this parasitic annelid, could actually have some medical benefits.0967

Phylum rotifer, these are rotifers, usually, you cannot see them.0973

The biggest one I have heard of is just a few millimeters long.0978

But others are microscopic, you need a microscope with like this view, to see them.0981

They are pseudocoelomates, they have a partial cushioning between their gut and their outer body wall.0985

They have bilateral symmetry just like the worms.0992

You could cut them in half, and you could see that there is a true left, a true right, there is the head end, there is the tail end.0995

Some of them are terrestrial, some of them you could find in damp soils 1002

because of their body structure and their difficulty retaining fluids, we need to be damp soil.1005

But a lot of them are aquatic like this one.1011

They do have a digestive tract, mouth, pharynx, an actual gut region with intestines and anus.1014

Look, right here, there is a crown of cilia.1023

If this is a live actual shot, you would see this, the cilia just constantly doing this.1027

They are bringing organisms in, anything that passes by, they can suck in.1032

They are just in the pharynx region.1036

Right here are jaws, they look kind of like little units just going like this, just chopping.1039

As food is drawn in, they chop it down and they can absorb the nutrients in their gut region.1045

They do move with a fraction motion, like you can see them kind of do these quick movements with the video.1053

They do have toes, it is not easy to see but if you were to zooming into here, you would see that looks like that, like little toes.1058

At the same that it can anchor itself on the substrate.1068

This actually is holding on with its little toes in this area, and it is reaching out in getting food.1071

There are interesting video clips where you can actually see the head part, 1078

contract into the body briefly, and then come back out and display its crown of cilia.1081

Many of these reproduce sexually, there are males and females.1088

Oftentimes, the males only exist to fertilize females, and they around for a brief amount of time.1091

They are just there for fertilization purposes.1099

Also, parthenogenesis is quite common.1102

Genetic evidence and studying these over time had shown that, there some species of rotifers that are only female.1106

And as far as we can tell, there have not been males for a long time, for thousand of millions of years.1117

Some species are only female, and that is very rare with animals.1124

But, if females can egg more females, you do not really need males.1128

Phylum mollusca, this is the first slide regarding mollusks.1137

Snails, slugs, clams, oysters, octopi, squiq, etc, those are the major ones, I will mention more on the next slide.1141

They are all coelomates, they all have that fluid filled cushioning, whether it is a snail or a clam.1147

Terrestrial, they are plenty on land, we have seen snails, we have seen slugs.1154

Oceanic and aquatic, the vast majority of the types of mollusks that you see are found in aquatic environments.1160

The mantle is a structure that they all have in common.1169

It is a membrane surrounding their internal organs and helps get gases.1173

Nourishment, in terms of the gases they need into their organs.1180

The mantle is definitely an important part of all mollusks.1184

They also have a muscular foot and a shell.1188

Some of them do not have a shell, some of them it is highly reduced and soft.1191

In the octopi, it is not there at all.1195

In the slug, it is not there.1197

But these are the classic three that they tend to have.1199

The mantle surrounding their organs, muscular foot which on a snail, if you turn this over, 1202

here is this little head with its sensory organs.1210

On the other side, it kind of looks like that.1214

Its muscular foot makes these motions to move it and it secretes mucus to help aid in its movement.1217

The shell, this is actually a slug, not a snail, it is not going to have one.1224

The shell is a classic mollusk structure.1229

You see it on snails, you see it on clams and oysters.1233

You see it with the chamber nautilus which is related to squid and octopi.1236

Based on fossil evidence, evolution biologist is studying these enough.1242

They are pretty sure that the original mollusks, the ancestral mollusks had a shell.1250

And that in some of them, the shell has gradually got reduced1255

or it is been missing in modern day species because they do not need it.1258

Certain mutations and continues success of those without the shell makes it happen.1263

They have a full digestive tract with specialize organs.1269

The interesting thing about snails, here is a little snail.1272

Obviously, their mouth is here and then inside the shell area, 1280

where you have that mantle under the shell, you have the digestive organs.1289

Right here, right behind its head is its anus, that is actually the exit hole.1292

Their waste just kind of comes out there, it is ironic that they realize how gross that is.1299

But the reason why they have this twist in their digestive organs is called torsion.1306

Gastropods, which you will hear more about on the next page, they typically have torsions.1313

It is kind of 180 degrees twist that happens with its organs.1318

The shell develops from a different process.1321

The shell shape is not due to torsion.1324

Anyways, radula is quite common.1327

If you were to zoom in to the mouth area of the snail, you have this kind of looks like a rotating chainsaw type unit, 1329

that allows it to bring food in and slightly grind it as it is doing that.1345

The radula in some most mollusks, it can be like a piercing unit.1352

Squid and octopi may take organisms into where their mouth is.1356

They kind of puncture it with their radula movement, like they are chewing on it.1361

Some are filter feeders, when you look at clams, oysters, scallops,1367

they take water in and filter out nutrients from the water.1373

Open circulation is common, meaning a lot of them do not have true blood vessels throughout their body.1377

Slugs and snails, they have open circulation.1383

However, close circulation is necessary in the cephalopods.1386

They have bigger brains, you will hear about those in the next slide.1390

Gills are used in respiration, the gills in the aquatic ones is obvious,1393

in terms of like having water in getting oxygen into their bodies from there.1401

Moist environments are required for the terrestrial ones.1408

If they get into a position where they are too dry, that can result in death, 1411

the inability to retain water and adequately get oxygen out of the air.1417

Usually, when it is really dry out, snails are inside their shell, underground, in a place where they are not going to dry out.1421

Excresionephridia, we have seen this word before in nephridia.1431

By the way, this comes from the same root as nephron.1434

Your kidneys, my kidneys, they have nephrons as the individual filters, there are millions of them in your kidneys.1439

Nephridia is close to it, in terms of them making metabolic waste and excreting it.1445

Well develop senses in some, it really depends.1452

With clams and oysters, some of those bivalves, they are just sensitive to lights.1454

They can tell when it is day time, they can tell when it is night time, that is about it.1459

There are others that can see very well, octopi, squid, they have well developed eyes.1463

More mollusks, sexually production is common.1471

External or internal fertilization, typically with the clams, the aquatic bivalves,1474

they are squirting their sperm and egg in the water, that is external.1482

With snails, slugs, octopi, squid, they do internal.1485

They actually do fertilize the female directly, by putting sperm inside of her.1492

Major classes of mollusks, gastropods which really means stomach and foot, is snails, slugs, noodabrank.1498

What is a noodabrank?1506

This is noodabrank, this is just one of many awesome pictures.1508

I would suggest you look up noodabranks online, there are so many cool pictures.1511

They are toxic sea slugs, they are usually hermophridic.1517

This bright colors indicate, do not eat me, I am toxic.1522

They have a lot of external gills and well developed sensory organs, really beautiful bright sea slugs that are toxic.1527

Bivalvia meaning two shelled, there ire also univalves, that is a nickname for them,1537

like abalone which has a single shell, the fleshy photos underneath it, the muscular foot.1543

But bivalves, clams, oysters mussels, scallops.1548

Here are some scallops, they have been known to skitter across the ocean floor, 1553

meaning the muscular foot allows them to stay close and clam shut.1557

But if they move it really quickly, they can look like they are running across the bottom of the bay or the ocean.1561

Also, a muscular foot can allow a clam to push itself deeper underground, 1570

to protect itself from predators that are on the surface of the ocean floor.1575

Cephalopods literally meaning head foot, and they have well develop heads, well develop brains.1581

Octopi which is plural for octopus, octopuses are also an acceptable word.1587

Squid, cuttlefish not actually a fish, that is a misnomer, it is not named correctly.1592

This is not a fish, it is actually related to squid, and then chamber nautilus.1597

A chamber nautilus has retained its shell, it is the only cephalopod that has a hard shell.1601

It has a lot more tentacles coming out.1608

Very smart, if you are to look at them, you would think that they are not tentacles.1611

They do not look tentacles, but they do have a little bit brain and eye sight.1615

Cephalopods, it is typical for them to have a siphon, this tubular structure inside of the tentacle area1620

that squirts water out and helps them propel themselves.1626

Some cephalopods do not have a siphon or it is highly reduced.1632

They have to rely on moving their tentacles.1635

Or even some of them, like the dumbbell octopus actually has little fins that allows it to move.1639

Like I have said before, big brains in cephalopods, and because of that they have closed circulation, pretty smart.1646

I have read that new evidence about an octopus, in general, it tells us, just as smart as dogs.1661

It might be hard to believe but think about this, humans has spent tens of thousands of years with dogs,1668

that is how they got domesticated from out of the wild.1675

We know that firsthand like, this dog is smart, thought it tricks, etc.1677

The amount of time we have spent with octopi is a lot less.1682

But as time goes on, we stayed with them and realize an octopus is pretty capable of some interesting things in problem solving.1687

Phylum arthropoda, the arthropods, insects, arachnids, crustaceans, and more.1697

The most abundant animal phylum on the planet, 70 to 85% of all animal species.1702

Just a beetles is hundreds of thousands of species, just them.1710

They are successful, they are coelomates, fluid filled cushioning, separating their internal body cavity from the outer.1715

Terrestrial, oceanic, aquatic, found everywhere, and they fly, some of them.1722

Segmented bodies with joint appendages.1726

You are seeing that in this picture, head, thorax, and there it is, and abdomen.1728

Some of them like, when we look at the lobster, they will combined the term, with head and the thorax, they call it a cephalothorax.1750

Just making note that some of them have a cephalothorax.1758

Head and thorax kind of connected to each other.1766

But same ancestors, the lobster and this thing.1769

Exoskeleton, they have an outer hard body wall, a protective coating, in a sense, around its body.1773

The exoskeleton is made of chitin, one of the many pieces of evidence telling us that chitin in fungal cell walls, these animals have chitin.1782

We are related to fungi, at least a little bit.1792

Molting, because they have this hard outer body protection, that prevents them from growing.1795

If they are hard from the outside, it cannot grow.1803

They molt, they shed this hard outer covering, when it is soft for a while, it allows some increased growth.1806

If it then hardens again, they molt again.1813

There are some fascinating images that you can look up where they show an insect, for instance, emerging from its molt, or a crab too.1815

I have read that soft shelled crab, if you eat that in a restaurant, the reason why it is soft shelled is1824

they took it out of the water right after it molted.1831

That is why it is a soft shelled crab, if you bite right through, it is a little crunchy but edible.1834

Full digestive tract, mouth, digestive organs, anus, animals are common.1839

It is like having little arms for jaws doing this, helping you munch.1848

It is very common in insects and spiders.1854

Open circulation, they do not have close blood vessels.1859

Unless, some evolutionary steps happen in mutations, you will never see a giant spider like in Sci-Fi movies.1864

You will never see one as big as a cow.1872

Without enclosed blood vessels and shooting blood around their body in a more efficient manner, you cannot get them that big.1876

Or you cannot get them having bigger brains without close circulation.1885

We do have open circulation, they have a cavity where blood gets pumped around and kind of slashes or bides the organs in nutrients.1888

Gills, tracheal tubes, or book lungs, this particular animal would have tracheal tubes.1900

Your trachea is right here, it is posterior to this area called larynx.1905

But, your trachea takes air into your lungs and out of your lungs, they are called the air way.1911

We have one trachea, tracheal tubes are these little pores, 1916

these little tubular structures found all through out the body of the insect.1920

It does not actually breath through its mouth for that reason.1926

It just gets air going into its body and out of its body.1929

Book lungs, you would see with spiders.1933

They are called book lungs because the membranes look kind of like a stack, like book pages.1936

The book lungs have blood vessels, at least blood flow because they do not have close circulation.1947

But they have blood going into that region, and an air in and out, it is getting oxygen in and CO2 out through the book lung area.1955

And then gills, you would see that in crabs, lobsters, etc., because they are oceanic.1962

More on arthropods, their excretion happens with malphigian tubules, or tubes rather, or nephredia, depending on the organism.1970

Malphigian tubes, you would see with insects, they do excrete it out of their body.1979

Here, we still do not see actual kidneys.1987

They have well developed sensory organs, typically.1991

An antennae are common, not all of them have antennae as you can see, spiders here, do not.1994

But you see them with lobsters, you see them with centipedes, you see them with insects, typically.2000

Antennae are another sensory organ that allows them to sense their environment.2006

Specifically, you can get reception of what are called feromones.2011

You will hear more about feromones later on in the lessons of this course.2015

They are chemicals that allow male and female can be attracted to another.2020

Antennae, sometimes you will get 4, two pairs of antennae, and sometimes just 1.2024

Sexual reproduction, separate sexes exist in most male and female.2032

It is very common for it to be internal fertilization.2036

They actually have the male get on top of the female and inject sperm inside of her.2041

Arthropod groups, crustaceans, there is a crustacean crab, lobsters, crayfish which can look like baby lobsters,2047

but they are separate species group.2054

Barnacles, pill bugs, barnacles may at first glance look like mollusks2057

because your average looking barnacle looks like a white volcano.2065

In a sense, you would actually see it on boats, piers, even stuck on whales.2072

Barnacles, they actually are hermaphroditic.2079

Their little mouths are what they are anchored on.2082

They are definitely crustacean but their body form has been reduced overtime.2086

Their ancestors probably had a head structure.2091

And maybe, they branched off from crustaceans a long time ago.2096

But genetically, not quite morphologically, but genetically they are definitely arthropods.2099

Pill bugs, you might have heard of these as rolly pollys, that is pill bugs.2105

Those are crustaceans that you actually find on land.2111

They do need water, they need moisture in the soil to survive because they have gills.2114

Arachnids, the eight legged ones, spiders, scorpions, ticks and mites.2119

It is common for spiders to have what are called spinnerets, little glands that would allow them to spin a web.2126

Some of them actually do have venom, some of them are poisonous.2134

Chenopods, centipedes like this one right here.2139

Diplopods, millipedes, main difference between centipedes and millipedes, there is a couple.2141

If you look at their individual segments, they have one pair of legs.2147

Here is three segments, 6 legs.2154

Here, carefully you can see that, their little legs move.2157

If you study them carefully, the movement of the legs looks like sign waves, like from calculus scraps, that is pretty interesting.2161

They are also carnivores.2170

Centipedes, a lot of them are venomous, they attack live prey and eat live prey, specifically other animals.2177

I have seen a video of a centipede just going down a tarantula.2184

The tarantula actually looks more harmful but the centipede kicked its butt.2189

They are like little fangs, in a sense, stuck it into the tarantula and inject with its toxin,2194

and just like paralyze it, as it got eaten.2207

Then millipedes, the diplopods, millipedes, I am going to use green because they are a little bit more peaceful, they are herbivorous.2210

They eat plant life or likens, when you look at each segment of a millipede,2220

you would actually see 4 legs, you would see two pairs per segment.2227

Does a millipede literally have a thousand legs? No.2236

Does a centipede literally have hundred legs? No.2239

You can count them, there is definitely not a hundred.2241

This is the designation, in terms of how they are different.2243

Insects, the arthropods have 6 legs, of course.2246

It is very common with insects to have a metamorphosis. 2249

For instance, a caterpillar is the larvae form of a butterfly or moth.2253

It will make that pupal stage, from larva you have a pupa, and they make a cocoon and emerge as adults.2261

The adult has 6 legs, with moths or butterflies, they have wings.2273

The purpose of an adult is to make more of these.2278

The larvae caterpillar just eats and eats, undergoes metamorphosis in their cocoon.2281

A lot of hormone signaling chemical changes that change their body style and they emerge as an adult.2287

The amazing thing is some adults actually have no mouth.2294

All the eating they did and needed to do was in this stage, as a caterpillar.2300

Their purpose for that, few days it is around as a moth is to go and mate, go make babies.2308

Next, phylum echinodermata, the spiny skinned ones, sea stars like you see here.2314

I do not call them starfish because they are not fish.2319

Sea stars, sea urchins, sand dollars, sea cucumbers like this.2321

They are deuderostomes like us, that is right.2326

They are all the ones I told you about previously in this lesson, are protostomes.2329

The original hole of the gastrula is the mouth, with us, it is the anus.2334

Radial symmetry, some of the larvae with this particular group have bilateral symmetry.2340

And then, that sort of head end goes away and they become this, it looks like a simpler body form as an adults.2347

Some of the theories about these original animal ancestors is perhaps,2354

the original one that leads all of these, way back then, had bilateral symmetry.2359

A lot of them retained that as adults, some of them like cnidarians and echinoderms not so much.2365

They have these reduced symmetries as adult and it pertains to their body movement.2372

Oceanic or aquatic, you are not going to see terrestrial versions of these.2377

You will find it in the ocean or lakes.2380

Water vascular system is unique to them.2383

They take water in and it circulates around the body, they do not actually have real blood.2385

The water vascular system allows them to transport nutrients and helps them move.2390

On the top, kind of off center, it is tough to see, but I will show you with this.2396

They have a region called a madroporic.2402

A madroporic is just off center from the very top middle which is where you will see the anus, the mouth is underneath.2405

The madroporae allows the water to come out of the water vascular system.2412

It is a regulatory opening, in a sense.2419

They do have an endoskeleton, you may feel a sea star and say it is hardly outside, it is an exoskeleton.2422

It is not though, it has a layer of skin superficial to that, technically, it is an inner skeleton which is what the endo part means.2429

Full digestive tract, it might be short but they have got a mouth, they have got at least simple digestive organs, and anus.2437

The anus is just a little off from where the madroporae is.2445

Tube feet, if you look underneath a sea star arm, or ray, you can call it, they look like rubbery tubey things that go like this.2449

And the way they actually get expanded to move down, think of having a balloon filled with air,2466

and squeezing the balloon, and having the balloon blew right here.2471

That is kind of what happens to move the tube feet.2475

They can be sticky and if you look carefully all the tube feet moving allow it to slowly move.2478

Some of them move a lot faster, not every sea star looks like it is moving slowly.2486

But the tube feet allow locomotion and they help with respiration, in terms of circulation of gases, oxygen and CO2.2491

There is a nerve ring, if I were to label the nerve ring, it looks like this.2501

It is very simple nervous system but it gets it done.2511

There is the nerve ring with its little extensions.2514

They do not have a true brain.2518

Sexual reproduction usually happens with separate sexes, some are hermaphroditic.2521

But regeneration is quite common, cutting a sea star and having its body parts come back, it has been observed many times.2528

Phylum chordate, this is our phylum.2538

All vertebrates, every single animal with a spine, and a few others, are considered chordates.2542

Like echinodermata in the previous slide, deuterostomes.2548

Bilateral symmetry in all of them, there is a head end, a back end, a left and a right, a top and a bottom, dorsal and ventral.2551

Terrestrial, oceanic, aquatic, and some of them fly, of course.2561

You can find them on every continent, and virtually, in every environment.2565

Four main body parts in common.2570

This is going to seem simple but there is a lot of chordates, there is a lot of animals in this phylum.2573

These are the four things they all have, and you cannot say spine because there are some chordates that does not have a spine.2577

Notochord, you will see these in the next slide.2584

A notochord, it is what usually would become the spine, in most of them.2589

The notochord that developed in our embryo cells became hard.2596

It became bony and went around our spinal cord.2599

Notochord is what the term chordate comes from.2603

Then, we have a hollow dorsal nerve cord, meaning on the backside of all these animals, dorsal side, you have a nerve cord.2607

Oftentimes, yes, it is encapsulated in the spine, not always.2618

The dorsal hollow nerve cord, the hollow means there is a tiny hollow area called the central canal.2623

In us, you would see cerebral spinal fluid, CSF, inside of that canal.2632

Pharyngeal pouches which can become pharyngeal gill slits in actual aquatic organisms that retain their gills.2637

Right up in this area, you would see those pharyngeal pouches, what can become those gill slits for respiratory reasons.2643

A posterior tail, they all have a tail coming out of the back side.2652

With all of these, you have the characteristics of a chordate.2657

This right here is an old drawing of a very simple chordate body plan.2664

Here is the head end, you have a very simple skeleton developing.2669

Back side, you got basic little fins, dorsal fins, the cuttle fin at the tail end, etc.2676

This is just an old drawing but it got the notochord, it got the nerve cord, etc, in there.2684

I will show you an even better drawing on the next one.2692

With Phylum chordate, like I said, the vast majorities are vertebrates and that is because2696

under this phylum, we have subphylum vertabrata.2702

And then the ones that are not in subphylum vertabrata, they are technically invertebrates, 2706

they do not have a spine though they do have a notochord.2711

Here are two examples, the lancelet, here is the basic body plan of what it looks like.2714

Here is what we are seeing.2723

The notochord, this brown part it is labeled two, there is the notochord.2728

This typically, in us, in all spined individuals, would become that bony skeleton or at least cartilaginous spines, specifically.2741

That is wrapped around what is in yellow, this yellow part which is labeled with 3 here.2753

This number 3 which is labeled that yellow part, you can see that little nerves extending from it.2761

This is the nerve cord, dorsal, hollow.2767

You could see that it is in the dorsal side, it is in the backside, right, this is the ventral side.2773

Up in this region, near where you have these blood vessels, you would have pharyngeal gill pouches.2780

In the actual lancelet, this is an aquatic animal, they were retrained.2786

And of course, there is a tail.2792

If you are wondering, what the heck is this?2794

Here is an aquatic area, here is the water right here, and this is the soil where the actual lancelet will just chill.2797

Here it is, this is the lancelet, it has little cilia like structures coming out of its mouth, brushing food in.2817

As things come by, it will spend a lot of its time in there.2827

The amazing thing is, we are more related to this than all the other animals in the animal phyla.2833

It has these four characteristics notochord, nerve cord, pharyngeal gill pouches that actually becomes slits, in the post anal tail, number 4.2839

It has all those things and retains them as an adult, it is in our phylum.2850

Next, even stranger, this a tunicate, I know it looks like a sponge, it is not.2855

Tunicates are in the ocean, typically.2863

As an adult, do not have a notochord or nerve cord or tail.2868

They do have a gill region that allows them to get gases in their body and expel CO₂.2875

The reason why this is a chordate is, it has all 4 classic characteristics as a larva.2881

Because the larva actually looks kind of like this guy, when it is a little baby2898

has all 4 of those characteristics that I mentioned on the previous slide.2902

When it develops as an adult, even though it loses 3 of them, it is still considered part of our phylum.2905

In terms of how it develops, it has a lot of similarities.2911

We probably have a similar ancestor long time ago, but we do have some stuff in common.2915

Thank you for watching