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Lecture Comments (1)

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Post by Bryan Cardella on May 1, 2014

NOTE: When I stated that killer whales "exclusively feed on fish", I should have said that they exclusively feed on animals.  Yes, fish will be eaten by them, but they have been known to eat much larger organisms, like seals!


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  • Intro 0:00
  • Mammary Glands and Hair 0:04
    • Class Mammalia Name
    • Hair Functions
  • Metabolic Characteristics 3:58
    • Endothermy
    • Feeding
  • Mammalian Organs 8:43
    • Respiratory System
    • Circulation
    • Brain and Senses
    • Glands
  • Mammalian Reproduction 12:55
    • Live Birth
    • Placental
    • Marsupial
    • Gestation Periods
  • Infraclass Marsupialia 17:42
    • Australia
    • Uterus/ Pouch
    • Origins
    • Examples
  • Order Monotremata 20:21
    • Egg Layers
    • Platypus, Echidna
    • Shoulder Area Has a Reptilian Bone Structure
  • Order Insectivora 22:21
    • Insectivores
    • Pointy Snouts
    • Burrowing
    • Examples
  • Order Chiroptera 23:32
    • True Flying Mammalian Order
    • Wings
    • Feeding
    • Examples
  • Order Xenarthra 25:14
    • Edentata
    • No Teeth
    • Location
    • Examples
  • Order Rodentia 26:33
    • 40% of Mammalian Species
    • 2 Pairs of Incisors
    • Examples
  • Order Lagomorpha 28:06
    • Herbivores
    • Examples
  • Order Carnivora 29:19
    • Teeth
    • Examples
  • Order Proboscidea 30:37
    • Largest Living Terrestrial Mammals
    • Trunks
    • Tusks
    • Examples
  • Order Sirenia 32:01
    • Large, Slow Moving Aquatic Mammals
    • Flippers
    • Herbivores
    • Examples
  • Order Cetacea 32:46
    • Large, Mostly Hairless Aquatic Mammals
    • Flippers
    • Fluke
    • Blowhole
    • Examples
  • Order Artiodactyla 34:30
    • Even-Toed Hoofed Mammals
    • Herbivores
    • Sometimes Grouped with Cetaceans
    • Examples
  • Order Perissodactyla 35:57
    • Odd-Toed Hoofed Mammals
    • Herbivores
    • Examples
  • Order Primates 36:30
    • Largest Brain-to-Body Ratio
    • Arboreal
    • Nails
    • Examples

Transcription: Mammals

Hi, welcome back to, this is the lesson on mammals.0000

When we look at mammals, where did the name come from?0006

It is mammary glands, it is milk.0009

We are first going to talk about mammary glands and hair,0011

which is another thing that mammals have as a unique characteristic within their class.0014

Class mammalia is named after the fact that mother’s give milk to their young with mammary glands.0020

It is typically delivered via nipples.0025

The reason I say typically, it is true that there are some that mammals out there that do not have nipples.0027

One example is the platypus, the female ductoplatypus actually does not have nipples.0034

She just secretes the milk out onto her fur and the baby laps it up.0039

She has mammary glands from around the armpit down to her lower leg.0045

There are some varieties, in terms of delivering that milk.0049

The majority of mammals do have a nipple structure for the baby to grasp on and suck from that.0053

If you look at this little diagram here, this is what the gland looks like beneath the skin.0060

Here is that tit, here are lobes of the tissue that is actually producing the milk.0065

You have milk developing in here, there are these little canals that bring it down into a sinus and it gets stored there.0072

When a female is nursing, typically, these will get filled, and when it is time for them to get emptied,0079

the baby will latch onto the tit, to the nipple area and start sucking.0085

That is a very common thing, it is the way that mothers nourish their young.0090

Milk has, not only carbohydrates, it has fat, proteins.0094

Even, you can deliver antibiotics and hormones to your baby0101

that makes them more healthy and encourages bond between the mother and the baby.0104

There are lots of advantages to natural breast milk.0110

Hair has numerous functions, it is not just for keeping them warm.0113

That is a major one, insulation.0118

Insulation, keeping warmth in, if you have a dog with a really shaggy fur,0122

and it is summer time, give him a haircut, they can cool off a little easier because of all that hair.0129

Camouflage, some of them have this ability to blend into their surroundings, thanks to their fur and the coloration of it.0138

This particular fur patch here, when a bunch of these mammals are together,0145

it will be hard to tell them apart and tell how many there are.0150

Also with stripes, sometimes with grasses or the terrain, it is much easier for the animal to blend in.0153

Sensation, definitely the feeling ability, when something just barely grazes a hair, that is connected inside the skin.0161

It would stimulate nerve endings.0169

That is true for us too, if something barely grazes against a hair, we know what that is like.0171

Waterproofing, having that fur can definitely aid with waterproofing.0176

With some animals, if they spend a lot of time in water as a mammal, having less hair may benefit them though.0183

Because having a lot of hair when you are swimming all day long can create drag,0191

you will not be able to go as quickly through the water.0196

When we look at dolphins and whales, that is a good example.0199

Signaling, there are definitely ways that animals can signal each other with hair.0202

If you have a pet cat, and your cats done that thing, it had its hair stand up on end,0207

that is a sign to other animals, and cats especially that it is not playing around.0214

Defense, definitely with the porcupine, that is a classic example.0221

Here is a porcupine, they have quills, these hairs that can actually be shot out and stick into a predator.0227

And that is a way for them to not get eaten.0235

Metabolic characteristics of mammals, here we go.0239

Endothermy, they are endothermic.0242

The nickname for that is warm blooded.0245

I explained it in a previous lesson how cold blooded and warm blooded is not the best term.0248

I do not want you to misinterpret this and think that0253

all warm blooded mammals are always hotter on the inside than all cold blooded animals.0256

That is not true, warm blooded is a nickname meaning that they are able to actually heat up0260

or cool down their body when necessary, based on changes in the external environment.0267

There are lots of ways to do that.0273

If you think about us, sweating is a way that we can do that.0275

Shivering is the opposite, in terms of heating up our body.0279

Adjusting our blood pressure can definitely change how much we are losing or retaining.0283

Feeding, in terms of them getting energy in their body.0288

The organisms that are being eaten, they can be insectivores because they are eating insects.0292

They can be herbivores, eating plant material.0299

Carnivores, eating other animals.0302

Omnivores, omni is what we are, or naturally we are supposed to be.0304

Omni means all, humans are meant to be omnivores, eating animal tissue and plant tissue.0308

Digestive tract length, length does actually relate to these.0316

When you look at an herbivore’s digestive tract, if they are strict herbivore,0320

especially with ruminant digestion, which I’m going to cover in a second.0325

They have really long intestine, it takes a lot longer to break down a plant material0328

and get energy from those monosaccharides contained in the cellulose in that plant cell wall material.0333

When we look at an omnivore’s digestive tract, generally, it is in the middle, in terms of overall length.0341

A carnivore’s digestive tract is significantly shorter, in terms of the amount of tissue0347

and time required to break that stuff down and get it absorbed into the bloodstream.0352

Ruminant digestion, this is another variety, in terms of certain herbivores and what they are eating.0359

With a lot of the hooved mammals, they are eating a lot of plant material, leaves specially.0365

Leaves are high in cellulose, in terms of the mass of the leaf, and what it is got going on there.0371

Cellulose is that plant cell wall material, it is indigestible to organisms like us.0377

For us, it would be fiber.0381

It just runs right through us, we cannot break it down with individual sugars for energy, that is okay.0383

With them, they are depending on those individual sugars to actually get energy.0389

What happens is, ruminants have a special kind of bacteria in their gut that helps them breakdown that cellulose.0394

A bacteria assists with breakdown of cellulose.0402

And then, they actually will regurgitate, what is called their cud, chew it again, swallow it,0413

and they can do that several times.0425

They spend a lot of their day eating but they get enough energy out of it.0427

Thanks to the ruminant digestion and that bacteria in their gut, they can take advantage of the glucose that is inside of cellulose.0431

With teeth, compared to the teeth in reptiles or even the teeth in frogs and amphibians,0439

you see a lot more variety, in terms of teeth structure in mammals.0446

They are well adapted to what they eat.0450

The types do pertain to their diet.0452

Here are the four main types, canines, incisors, pre molars, and molars.0455

I’m giving you a couple of examples here.0459

You can see with this particular set of teeth, this is a carnivore.0462

You can see there are plenty of sharp teeth.0469

It needs those to bite down into its prey.0473

You can see they have large canines and sharp teeth, even when you go a little further back towards the premolars.0476

Here, this is actually the teeth of a mouse.0484

They do have the sharp incisors in the front and you will hear more about rodent teeth, later on in this lesson.0488

They do have a lot of teeth towards the back that are modified for grinding plant material, grains, and such.0493

The animals that spend a lot of time eating plant material tend to have flatter teeth that are meant for this grinding.0502

Of course, animals with a more sharp teeth, they are meant for tearing flesh.0510

We have teeth modified for an omnivorous diet.0515

We have some sharp ones at front but definitely the flat molars in the back.0519

Mammalian organs, the respiratory system.0525

This is a major difference from the other ones we have seen, in terms of the other classes of vertebrates.0528

Class mammalian, you have animals that have lungs with a diaphragm.0533

The diaphragm is this dome shaped muscle that is underneath the lungs, on top of where we have the liver and stomach.0538

Every time you breath in, it contracts and allows us to expand our lungs more.0547

It also is protective, in terms the bottom part of this thoracic cage being enclosed.0553

The diaphragm in mammals, it is unique to us.0560

Circulation, we have a four chambered heart.0565

That is true of the mammals in general.0567

Like I mentioned before with birds, two atria on the top and two ventricles left and right.0573

The great thing about that is, I will actually cover for you.0581

If we were looking at a heart, like you are looking straight at a human here.0585

I’m coloring this side red because this is the left side, as if you are looking straight at a person.0590

My left is over here but to you it is your right.0598

The left side actually contains the oxygenated blood, that just come back from the lungs.0601

It will pump it to the rest of the body.0607

This side, the right side of the heart separates the deoxygenated blood, and that is a good thing.0609

The right side, the right atrium, right ventricle receives blood that has come back from the body without the oxygen it needs.0616

This will go back to the lungs and end up going to the left side of the heart.0624

The brain and senses, in terms of mammals having some differences.0628

The cerebral cortex is well developed, even through sheep brains.0633

Here is the human brain, sheep brain, it is oriented a little bit differently because their posture is different.0637

Their brain stem and their spinal cord comes out at a different angle.0643

We still have vertical convolutions, these wrinkles in the outside of the brain.0646

And, that increases the surface area on this part that pertains to problem solving, intelligence,0651

and reacting in very novel ways, in terms of solving problems.0657

The cerebral cortex is where the majority of your thinking actually happens on the surface.0662

If it was not for all those wrinkles, you would have less tissue there.0667

If you check out a reptilian brain, an amphibian brain, or a fish brain,0670

not only they are smaller on average, but the top of their brain looks smoother.0675

They do not have these convolutions like mammals do.0680

I actually dissected pigs numerous times, it is incredible how similar a pig’s brain looks to a primate brain like ours.0684

The cerebellum is well developed.0691

The cerebellum is like a mini little cerebrum.0693

Here is the cerebrum, cerebellum.0696

This is great for coordination and balance in what we do, very important structure.0702

You will find it in other vertebrates but on it is a little bit more well developed in class mammalian.0710

Gland differences, the mammary glands, the ones that produce milk and secrete milk for babies.0716

Scent glands, in terms of attracting others, releasing pheromones.0724

You can see a deer doing that, and other animals leaving scents for others to discover and mark their territory.0731

And then oil, there are glands that secretes different kinds of oils.0737

One of the many ones that we have are called ceruminous glands.0742

Ceruminous glands, they make that wax in our ear.0747

The wax build up is called cerumen.0751

We also have sebaceous glands which are associated with hairs.0761

This will secrete oily substance that covers and protects our hairs.0768

These are just two of many different oil glands you can find in mammals.0771

Mammalian reproduction, all mammals have separate sexes with internal fertilization.0776

Live birth is typical, that is no surprise, we know that mammals give birth.0783

The female just releases the baby outside of its body.0788

Typically, we are not talking eggs, but there are few mammals that do lay eggs.0791

Most mammals are placental, a placenta is a way that the blood supply of the female mother0797

and the blood supply of the baby can be connected via this tissue right here.0805

Here is the inside of the uterine wall, the womb, and you have this placenta anchored there.0809

You can see that this is the umbilical cord.0816

This is actually an image from Gray's Anatomy, not the TV show.0818

Gray's Anatomy is the original classic anatomy textbook, very detailed, great drawings.0825

This is from Gray's Anatomy, you could tell by the style of the drawing and the writing.0833

You have umbilical veins and arteries that are taking blood, specifically nutrients and oxygen0838

from the mother's blood into the baby's body, and vice versa.0847

The baby's CO₂ and waste will actually go out from the baby's bloodstream, back into this area, and go into the mother's body.0851

You could see that there is this ability for blood to have its material cross into these little areas here and into the baby.0858

That is the placenta, once the baby is born, the placenta will come out afterwards, it is called the after birth.0868

The majority of mammals do that to nourish their baby inside the mother.0874

Other mammals are marsupial, they do it a little bit differently.0880

The baby initially develops inside the uterus, but then, instead of making this placenta that we see here,0884

the baby emerges as a tiny little baby.0891

Sometimes, it will be stimulated to crawl up in the pouch or the mother will assist it in the pouch.0896

One of the ways that I have heard is the mother will actually lick a path with her tongue, that the baby can follow to the pouch.0901

There are nipples inside of the pouch inside of the mother, the baby will go in there and nurse,0908

and grow until it can no longer fit in the pouch, and then, the mother will make it get out.0914

That is how the marsupials do it.0920

And then, some lay eggs.0922

It is called order monotremata, this is the monotremes.0925

I will tell you more about those in a bit.0930

They are considered an ancient lineage of mammal because we think that the very first mammals0932

would have laid eggs because they came from reptiles.0939

Eventually, there were benefits to keeping the baby contained inside of you until it is ready to come out.0943

You can imagine some of the benefits of doing that, in terms of protection and nourishment.0949

There is less danger of a predator getting them, when you are carrying around the baby inside of you, rather than laying it in a nest.0953

The monotremes like the platypus and the echidna, they lay eggs but they are still mammals.0962

Gestation periods, this is like saying how long does pregnancy take.0966

The gestation period, the trend is the smaller the animal, the shorter the gestation period.0970

Let me give you two examples, a small and big one.0977

Rabbits, I have pet rabbits growing up.0980

After they have sex, it takes a little more than 30 days, that is all it takes.0984

Less than a month and 1/2 for babies to be born, from sex to birth.0990

Because the baby, when it comes out is pretty tiny relative to some other mammals.0994

It is a matter of how long does the mitosis take, how long does the organ development take inside the womb before it is ready to be born.1000

They will be born fragile but soon thereafter, they are ready to hop around and they are good to go.1007

But an elephant is a different story, elephant is the largest land mammal on earth.1014

Its gestation period is 22 months, that is almost two years.1020

It is because elephant’s cells are not any bigger than rabbit cells.1027

They just need to make more of them, more mitosis.1032

They need to make a larger baby inside of themselves, that takes more time.1034

Almost two years, typically for an elephant.1039

When we look at humans, it is around 9 to 9 ½ months, 40 weeks to be exact.1042

Other animals that are similar in size to us, may be close, in terms of their gestation period.1048

There is this trend, it is not always true but generally, the bigger the animal, the longer the gestation period.1055

The different groups of mammals.1064

This is an infra class, within the infra class, meaning this is right below class mammalian, it is contained within it.1066

You would see different orders of marsupials, I will not get into all of those.1073

I just want to talk about marsupials, in general.1077

They are mostly found in Australia and the surrounding areas.1080

There actually are some in North America, an example would be the North American possum.1085

They think that marsupials may have actually first evolved in North America.1089

Before the continents split, they are early ancestors ended up spreading out and end up being mostly in Australia.1096

That is under debate, it could be that they really did first come to be in Australia and just a few of them ended up in North America.1102

The majority are still in Australia today.1110

Uterus and pouch combinations, they do have a womb like other mammals, inside of the female.1113

Like I have mentioned earlier, with the gestation coming to completion, they finish in the pouch.1119

There is a pouch down there that has nipples inside of it, the baby grows in there.1127

In terms of origins, I briefly mentioned that a second ago, about did they first occur in Australia?1133

Did they first occur in North America? It is hard to say.1140

They are considered an older lineage because of this pouch thing.1142

It is tough to say exactly when they first appeared. With more fossil evidence over time,1149

we could probably pinpoint when they first came to be.1157

Definitely, an older lineage than this is the monotremes, which is coming up next.1162

Koalas, it is actually not really a bear, it is a marsupial that does have some morphological similarities to bears,1165

but it is a marsupial and has sharp claws.1176

They spend a lot of their day very tired and knocked out.1179

They will sleep over 20 hours a day, and they eat, typically, eucalyptus leaves and other leaves in their environment,1184

which can have a dozing off effect on them, supposedly.1191

This is actually called a cuscus, there it is right there, it is a marsupial.1196

This is a wallaby, you can see that its pouch is full, there is no baby in there.1201

A wallaby looks similar to a kangaroo but they are closer to the size of a large rabbit.1206

You have seen kangaroos before, of course, there is a gray kangaroo, red kangaroos, there are many species.1213

Of course, there are possums.1218

The monotremes, the most ancient lineage of mammals.1222

Order monotremeta, these are the egg layers, they are native to Australia and the surrounding area.1226

They used to be a lot more species based on fossil evidence and research, but their habitat is gradually being destroyed.1231

Because of poaching, unfortunately, some of them are endangered.1240

Actually, the majority of them are definitely threatened and endangered.1246

Here you have the platypus, right here is the platypus, the duck billed platypus.1250

Here you have the echidna, there is one remaining species of platypus, there are several echidna species.1257

The shoulder area has a reptilian bone structure, reminiscent of the reptile movement, in terms of articulating their legs.1266

That is more evidence that this is probably an earlier divergence from the reptilian ancestry that mammals have.1276

Their chromosome number is also very similar to reptiles, in terms of the exact number of chromosomes inside of their genome.1284

You could see that there are some major differences with how they look, the duck billed platypus.1292

The interesting thing is they are known to have a bony spur in their hind leg,1297

that can actually inject the toxin or venom in predators.1302

It might not be enough to kill a human, but a smaller animal trying to hunt them could be in trouble.1306

They are very social animals, they will play in the water and their mating behavior is very interesting.1312

When explorers first saw these from England, they thought it was a joke, it was like made up,1317

that someone had glued duck bill to something like a beaver.1324

But we know it is legit, this is a legitimate animal.1328

The echidna is different, it is not dependent on the water.1331

It has this longer snout and it is a very interesting little animal.1335

Order insectivora, they are insectivores, they mainly eat insects that is why they are called this.1342

They usually have pointy snouts and they are smaller than a lot of other mammalian orders.1348

You can see that little pointy snout here on the shrew.1354

Here we have a shrew.1357

Here is a hedgehog next to it.1363

They are found almost everywhere on earth.1368

A lot of different environments in lots of different continents.1370

Burrowing is very common with them, they tend to go underground for protection and caring for their young.1373

Certainly, if they can dig a burrow and hide in there, they are well off, in terms of staying away from predators.1379

Shrews like this one, they are tree shrews, I have read that the elephant shrew is actually extremely fast and agile1389

when it is running away from predators.1397

They have a good memory of the past they have created in their environment.1399

They know how to make quick turns and they can outsmart their predators very often.1403

Even though they are tiny, they can be very clever.1408

Order chiroptera, chiroptera is the bats.1413

There are 925 species and they are the only true flying mammalian order.1417

If you have heard of flying lemurs or other things that are called flying, like a flying squirrel, they just glide.1421

They are going to get falling quickly.1431

These actually are full-on flying many miles.1433

They have wings, these are modified arm bones with thin skin.1440

If you look carefully at a bat wing, you will see that there are digits corresponding to our bones.1442

They are just a lot tinier and spread out in this wing structure.1448

There is a lot of homology, and if you look at the evolution lessons in this course, more about that there.1453

The feeding ranges from being carnivorous and eating prey, to being fruit bats.1461

There are a lot of bats that depends solely on fruit and vegetation.1470

Some are vampire bats, they typically will not go after humans, that is very rare, it is hardly ever reported.1473

They typically go after cattle.1480

It is common for them to go after a cattle or steer, and go up to blood vessels near the neck region.1487

They will suck up their blood, they will secrete what is known as anticoagulant1496

to prevent the blood from clotting as they are lapping it up.1500

They do get nutrition from that.1503

Here we have the traditional looking bat flying around.1506

These are flying foxes, just hanging out.1509

Order xenarthra, are actually originally termed as edentata which refers to the teeth.1515

Order xenarthra, typically have no teeth or a simple pig like teeth.1523

It is almost un-mammalian to have no teeth but they still give milk to their young, they have hair,1530

they are related to us, they are mammals.1538

We have some that look very different but they are considered related,1542

in terms of finding other environments that have a similar ancestry.1546

Most are in Central and South America, here we have three classic examples.1551

Here is the anteater, here is a sloth, it looks like it is smiling for the camera.1555

Here is an armadillo, this is the one that you actually could find closer in North America to Mexico, in Texas, etc.1560

The armadillos, they can form a little ball, they have these banded plates here, like this may be the nine banded armadillo, I’m not exactly sure.1569

These are xenarthrans, little to no teeth but they get by, this one is eating insects, this one is feeding on vegetation.1580

They do not necessarily need the specialized teeth that other animals have in class mammalia.1588

Order rodentia, the rodents, 40% of mammal species are in this order, that is a lot.1595

The classic rodent characteristic is two pairs of incisors that never stop growing.1602

If you look carefully at their mouths, if this is the top and this the bottom of their mouth, you will see that here is the other nose.1608

This is a classic look that they have those little teeth in the front and they never stop growing.1621

They are grinding on things and they are eating a lot through the day because if they stopped grinding,1630

they would keep growing and cause them issues, in terms of jaw problems.1636

That is a really interesting characteristic that those teeth do not stop growing.1641

They are found in virtually every terrestrial habitat, we have all seen them, whether it is a squirrel,1646

a mouse, a rat, pet hamsters, those are all rodents.1650

Yes, rats like these, mice, squirrels like this one, chipmunks, hamsters, marmots, beavers.1655

This here, I did not list it but I will write down the name.1664

This is the largest living rodent on earth, this is the capybara.1667

The capybara is native to the Amazon, they actually do a lot of swimming.1674

They are about the size of a dog, a medium sized dog, pretty large the capybara.1679

Order lagomorpha, traditionally, a long time ago, these were considered part of the rodent group.1687

There are a lot of similarities but now they have their own order.1693

Similar teeth to rodents, in terms of the structure and that growing characteristic.1698

They have another smaller set of incisors behind those big ones, it is a little bit different.1703

They are typically herbivores, eating grasses, seeds, fruits.1709

If you ever had a pet rabbit, you know that they do not eat meat.1713

They are feeding on grains and plant parts.1716

The rabbit here is a lagomorph, hares, not like this kind of hare.1720

A lot of hares have very long ears, they have big ears.1726

It helps with dissipating heat out of their body.1729

This here is actually a pica, some people pronounce it pica.1732

But pica is actually a part of inspiration for picachu from pokemon.1738

If you just use your imagination, make it yellow with some black lines in the tail, or electricity, it is pretty close.1745

This is found in mountainous regions, it is pretty cute.1754

Order carnivore, the carnivores.1760

There are some carnivores that are not in this group, like a bat, for instance,1763

these in terms of their jaw structure and their history as organisms, in terms of their ancestry, there are some similarities.1767

They have teeth that are adapted to tearing flesh and they are carnivorous, like the name says.1776

All the dogs, canines, foxes, felines, all of your cats, wildcats, etc., bears, seals.1783

Interesting enough, seals and sea lions are more related to dogs than dogs are to cats.1791

Seals are like the canines of the sea environment.1798

Walruses, otters, weasels, skunks, minks, this is a mink down here, very similar morphologically to weasels.1802

Interesting enough, there are some drawbacks to the term carnivora.1811

For instance, the giant panda is in order carnivora but it is not a carnivore anymore.1815

Its ancestry does have similarities to the ancestry of these animals, but calling it carnivora, sometimes you are into trouble.1824

Yes, in general, order carnivora contains exclusive carnivores.1832

Order proboscidea, the largest living terrestrial mammals on earth, bigger than this would be certain whales.1838

They have long flexible noses, they are known as trunks.1847

A proboscis is meaning nose.1851

This extensive trunk is not only for smell, it is for feeding, washing, lifting things.1856

They will suck up water and spray it, they will use it to grab things.1865

It is like having another limb, it is like having a 5th limb.1869

There are tusks, that is the upper incisors extending out of their mouth.1873

That is a defense mechanism having those, made of ivory.1878

Poachers, unfortunately, will sometimes kill elephants for that, but they are now protected, thankfully.1883

This is an African elephant, this is an Asian elephant.1893

The African elephant has much larger ears.1897

Based on the climate it is found in, it is hotter there, it helps them dissipate heat.1899

They are typically a bit larger, in terms of their overall mass.1905

The back also looks different, see how the Asian elephant has smaller ears, that is one of the differences.1908

Also, the slope of their back is more rounded, that is another characteristic that you can differentiate them from African elephants.1914

Order sirenia, named after the ancient Greek siren, in terms of the singing and the noise.1922

They do communicate in the water with song, occasionally.1930

They are large, slow moving aquatic or oceanic mammals, that is kind of like the cows of the sea, in a sense.1934

The nickname is actually sea cow, for some of these.1942

Their forelimbs are modified as flippers, and they do not have hind limbs anymore, like some of the whales.1945

These are in their own order, they are not in any order with whales.1951

They are herbivorous, that is another reason why they are considered sea cows.1955

They are just grazing in the water and eating vegetation.1959

Here is a manatee and here is a dugong.1962

Next order, cetacean, the cetaceans.1967

These are large, mostly hairless aquatic/oceanic mammals.1970

The majority are in the ocean but there are river dolphins that are found in freshwater.1975

It is not as abundant as the dolphins that you would find in the ocean and saltwater.1980

But, they do exist there.1983

They have forelimbs like with the sirens, the sirenia group, is modified as flippers, as you can see here and here.1986

No hind limbs, those have been completely reduced and they are not absent.1993

Their tail is known as a fluke, if you look at the pattern, like the coloration on flukes in like whales,1998

for instance, supposedly no two flukes are alike, it is like their fingerprint.2004

A single blowhole on the top of their head for breathing, and they do go up for air.2009

You could see the exhaling and sucking in of air happen with that.2015

Some are filter feeders, they use something called bailey which almost looks like bristles of a broom.2019

When you look at various whales, they will filter feed by getting water in there and2025

they will actually feed on some of the smallest organisms in the water like plankton.2032

Some are predators, like the dolphin, like the killer whale which is actually more related to dolphins than whales.2041

They will go after fish exclusively.2047

Whales like this one, the blue whale, the largest animal on earth.2050

There are theories that it can be the largest ever, larger than anything that existed during the dinosaur era.2056

This dolphin, many different species of dolphins and porpoises are related to dolphins as well.2063

Order artiodactyla, these are even-toed hoofed mammals, they have hooves.2071

Herbivorous, they typically undergo ruminant digestion.2078

Earlier in the lesson, I talked about being a ruminant.2081

Animals like deer would definitely be doing that, cows, goats, etc.2085

Sometimes these are grouped with cetaceans.2092

You will see in some books they will write cetartiodactyla.2095

They are combining artiodactyla with cetacean.2106

The reason why they do that is, there is genetic and fossil evidence that whales, before they ended up exclusively in the water,2110

when they had forelimbs, they actually were related to the ancestors of these organisms.2118

It might be hard to believe, but if you lookup in the fossil evidence and genetic evidence, it is there.2123

It makes sense in the whole theory of things.2129

I’m teaching to you separately, the cetaceans we will say they are in one order and artiodactyls, they are on another.2132

Deer, like this one, antelope, moose, cattle, sheep, goats, pigs, camels, hippopotamus,2138

here we have a warthog, these are artiodactyls.2146

Since they are even toed, they typically have two or four toes in the hoofed region.2150

Order perissodactyla, these are odd-toed hoofed mammals.2159

We are talking 1 or 3, here is an example of one that has 3.2162

Modern day horses have one digit that makes up their hoof.2167

They are herbivorous and their teeth are adapted for grinding plants.2171

Even though a rhino can be very intimidating with their horns and such, they are not predators.2174

They are eating grasses, they are eating vegetation.2181

Horses, definitely eating vegetation.2184

Yes, the horses, zebras, rhinoceros, are perissodactyls.2186

Order primates, that is our order.2192

This is the largest brain to body ratio in any of the mammals.2195

Let me explain, if you look at whales, like a blue whale, is the blue whale brain larger than a human brain?2200

Yes, it is, the blue whale is humongous, they have a big brain.2206

But, when you factor the brain and body ratio, the mass of their brain divided by the overall mass, we are a bit better,2211

in terms of having a larger brain for our body size.2217

Primates, in general, big brains.2220

Most are arboreal, meaning in trees.2223

Their limbs and hind limbs are adapted for that.2231

A lot of them actually have opposable toes with their hind limbs, like this particular primate here.2235

It is adapted to life in the trees.2242

Orangutans still will spend a lot of time in the trees, they are found more on the ground than some other primates like this one.2244

Opposable like I mentioned, having them in the front with the forelimbs, we have those.2253

We are adapted now to walking on two legs.2260

We are bipedal, other primates are classically quadrapedal meaning getting around on four legs.2264

Even though you will see an orangutan or chimpanzee or gorilla, walking around on two, when they are going fast,2275

you will see them do what is called knuckle walking, they will be on their front legs.2282

Claws are less common compared to other mammals.2287

Having claws on mammalian toes or digits is actually quite common, especially with the carnivores.2290

Consider a lot of them are hunting live prey, they do have sharp claws.2297

It is more common to see flattened nails with primates, a little less dependence on hunting live prey.2301

Primates includes monkeys, apes, and humans.2309

Including a lot of human ancestors, the hominids that are now extinct.2313

Thank you for watching