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Lecture Comments (4)

2 answers

Last reply by: Hossain Khondaker
Tue Jul 28, 2015 10:34 AM

Post by Hossain Khondaker on July 26, 2015

What is the difference between oceanic and aquatic? is it just the salt concentration or is there more to it??

0 answers

Post by Bryan Cardella on March 14, 2014

NOTE:  When I stated that there are "some reptiles, like crocodiles, that are bordering on being warm-blooded", I was referring to the fact that crocodiles have a four-chambered heart (which warm-blooded vertebrates have).  However, don't be mistaken: crocodiles are definitely ectothermic. Modern-day reptiles are usually not able to regulate their internal body temperature enough to be considered endothermic (warm-blooded).  On the other hand, there are some ancient reptiles from over 100 million years ago that show evidence of being truly warm-blooded.

Animals, Part III

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
  • Characteristics of Subphylum Vertebrata 0:04
    • Vertebral Column
    • Neural Crest
    • Internal Organs
  • Fish Characteristics 2:05
    • Oceanic or Aquatic
    • Locomotion with Paired Fins
    • Gills
    • Fertilization
    • Movement
  • Fish Classes 8:58
    • Jawless Fishes
    • Cartilaginous Fishes
    • Bony Fishes
  • Amphibian Characteristics 12:22
    • Tetrapods
    • Moist Skin
    • Circulation
    • Nictitating Membrane
    • Tympanic Membrane
    • External Fertilization is Typical
  • Amphibian Orders 18:20
    • Order Anura
    • Order Caudata
    • Order Gymnophiona
  • Reptile Characteristics 20:31
    • Dry, Scaly Skin
    • Lungs for Gas Exchange
    • Terrestrial, Oceanic, Aquatic
    • Ectothermic
    • Internal Fertilization
  • Reptile Orders 26:28
    • Order Squamata
    • Order Crocodilia
    • Order Testudinata
    • Order Sphenodonta
  • Bird Characteristics 28:43
    • Feathers
    • Lightweight Bones
    • Lungs with Air Sacs
    • Endothermic
    • Internal Fertilization
  • Bird Orders 34:13
    • Order Passeriformes
    • Order Ciconiiformes
    • Order Sphenisciformes
    • Order Strigiformes
    • Order Struthioniformes
    • Order Anseriformes

Transcription: Animals, Part III

Hi, welcome back to, this is the lesson on animals, part 3.0000

When we look at subphylum vertebrata, the subphylum that all vertebrates are in, every animal with a spine,0006

there are some characteristics for you to keep in mind, in terms of how they are developed and what is inside of them.0011

The name comes from the fact that there is a vertebral column, spine, that has the spinal cord inside of it, protected.0017

It is going to be made of bone or cartilage.0023

Cartilage is soft bone, we see in a lot of fish, specially in the ocean with cartilaginous skeletons.0025

The majority of the species though, do have a hard bony spine that is protecting the spinal cord.0031

The neural crest, when we look at the development within an embryo, in terms of the layering,0038

there are some folding that happens with this neural plate, initially.0045

You get this fold and by convergence, they mean to say that, the little membranous areas are being folded together.0049

And eventually, it pinches off to form this neural tube, that neural tube is going to become the spinal cord.0057

Right next to it, there is an area called the neural crest.0063

The neural crest that develops from that nerve cord area helps form certain nerve fibers.0066

It is going to be connected intimately with the spinal cord.0072

Sense organs, allowing us to perceive the world.0074

Glands, various glands associated with these animals.0078

The internal organs that you are going to find in vertebrates are kidneys, liver, heart.0083

In a lot of invertebrates, you do not see those.0088

They have ways of getting waste out of their body, but it is typically with a simpler kind of tissue,0090

not an actual kidney containing millions of nephrons.0096

Liver is a way to detoxify the blood, to store various organic compounds.0100

And of course, the heart is going to be really efficient pumping organ0106

to get those fluids around the body quickly and efficiently.0110

Close circulation, you are going to see blood vessels, actual enclosed blood vessels coming out from the heart going back to the heart.0114

It is just a part of having a really efficient cardiovascular system.0122

Let us talk fish, these are the first vertebrates that existed, based on fossil evidence.0128

The first spine creatures were in the oceans.0133

When we look at fish today, they are oceanic or aquatic.0136

Keep in mind that, a synonym for oceanic, we can also say marine or the ocean.0139

Yes, a lot of them are in lakes, rivers, ponds, etc.0146

There are approximately 24,600 species, that is quite a bit.0149

Most of them have jaws, we cannot say that all fish have jaws.0154

Most of them do, but I will give you an example of a fish that actually has a sucking ability, 0158

that does not have the actual clamping down ability.0164

And we think that jaws gradually evolved in fish hundreds of millions years ago.0168

Where we had parts from the area that was associated with gill regions,0174

gradually get larger and start articulating with other bony parts.0180

And it takes a lot of mutations, of course.0184

Over thousands and thousands of generations, you gradually had jaws developing.0188

There are lots of benefits to having those.0193

Locomotion with paired fins, when we look at the average fish, let us take a loot at this one right here.0195

Dorsal, when we look at the dorsal fin that is on the dorsal side, that is the one backside.0201

A lot of people talk about the dorsal fin of the shark, they can see it coming out of water or a dolphin’s dorsal fin.0206

The pectoral fins, those are the ones up here, associated with that pectoral region.0214

The ones that are kind on the side that we typically see close to the gill region, those are pectoral fins.0219

The pelvic fins, here is a pelvic fin, right here on that fish.0226

Anal fins back here, and then cuttle fin, the back tail fin, cuttle means tail.0231

Scales, of course their skin has this scaly appearance, to us, it can be very smooth, depending on the fish.0239

Some scales are actually very tough especially the ones on sharks.0246

But they scales protective, allows them to efficiently move through the water.0250

They have many important functions in fish, of course.0255

Gills, fish have gills for exchange of gases.0258

Since, the average fish does not have a lung, this is how they get oxygen in their body, this is how they get CO₂ out.0262

The average fish is gulping water and if you look in a fish tank, what fish are doing, you can see them doing that.0267

The water going in their mouth goes through the gill region.0275

What they have in there is this thin filaments covered in lamellae.0278

If you were to look closely at the gill filaments, they have these little units extending out.0282

If you zoom into one of them, you have these plate like lamellae lined up, each one is a lamella.0291

These lamellae have veins and arteries going by them.0304

I’m using red and blue for artery and vein.0315

You have the blood vessels going by and you have what is called counter current exchange, 0319

in terms of the flow of them by each other.0323

And that is what allows oxygen from the water to enter the bloodstream,0327

and CO₂ from the bloodstream, their waste, to go back into the water.0331

The water that passes out of their gills is like them exhaling.0335

Instead of having a lung, it is just another way of doing it.0339

in terms of having the water rushed by those blood vessels, getting the O2 in, getting the CO₂ out, that is how gills work. 0342

They have circulation with the two chambered heart.0352

They typically have one atrium on top and one ventricle on the bottom.0354

You are going to see in other animals, other vertebrates, later on,0361

that some of them have a three chambered heart where they have two atria and the one ventricle.0364

The others have 4, like the average bird and mammal.0369

But you know, they get by with the two chambered heart, 0373

it is not as efficient as some of the other animals but they get by with it.0376

The single loop circulation, what that means is, there is one loop of blood going around their body.0380

The heart pumps into the gills, goes back to the heart, pumps to the gills and goes back to the heart.0386

As it is going through their body, it is oxygenating their tissues, 0389

it is picking CO₂ up from their tissues, bringing that back to gill region.0394

You are going to see in other animals like birds, mammals, etc, there is this two loop system, 0398

where there is one loop, where the heart is going to the lungs, in terms of getting the blood to the lungs and back.0405

Then, there is this other loop where the heart is getting blood to the rest of the body and back to the heart.0412

This is actually a single loop system, in other animals we will see a double loop.0416

Fish have well developed senses, not only vision but they have olfaction.0421

This means smelling, a sense of smell.0426

In the water, smell can be very obvious.0433

There is a lot more molecules, smells can be sensed very quickly, and in small amounts.0438

They definitely can smell when there is a predator coming, or they can smell when they are actually the predator looking for prey.0445

You may have heard that sharks, just like a single drop of blood in thousands and thousands of gallons of water, 0453

or liters of water, they can smell it, and they know that prey is nearby.0459

The lateral line is this line along a fish’s body that is sensitive, in terms of them noticing movement in the water.0464

If you ever wondered how fish can just so easily notice the slight movement into the water, 0475

it is their lateral line, in communication with the nervous system.0478

Compared to us, if we are in the water and just kind of watching, a fish is way more sensitive to slight movements into the water.0483

In terms of survival of the fittest in the water, it is very important, it is the lateral line.0490

Fertilization, in terms of them making babies, most of them are doing external fertilization, releasing sperm and egg into the water.0495

But there are some that do internal, sharks for instance, do internal fertilization.0503

Movement, they are swimming in the water with their fins but one thing that is unique to fish is the swim bladder.0509

It is an organ that actually can take in gas and release gas.0517

Depending on how much gas they have, they will rise, they will get more brilliant in the water, or they will drop.0520

The more gas they have inside the swim bladder, they can rise more easily, closer to the surface of the water.0526

And the opposite is true, when they release the gas from that swim bladder.0534

Fish classes, these are the major fish classes in the whole fish group.0540

Jawless fish, as I mentioned that there are fish out here that do not have a jaw.0549

Here is an example, look at this picture, that is what is called a lamprey.0550

If you are wondering kind of a more specific name for its class, this is considered an agnathin class, agnatha.0555

Hog fish, similar in the case that they do not have a jaw, they have this sucking ability.0566

They actually, hog fish release this very nasty slimy substance, as part of the defense mechanism, not very pleasant.0573

But lampreys, they will suck on prey with their mouth sucker region, they do not have a jaw.0580

I have actually seen pictures of other fish, like bony fishes, that is being taken out of the water.0588

A lamprey actually stuck in the gill region, sucking out of there.0594

And that is the spot they want to be, if they are actually sucking blood out of the fish and they want get oxygen and nutrients.0598

Cartilaginous fishes, by the way, if you have ever heard that the word fishes is not a word, 0606

it is when you are talking about numerous species of fish.0611

School of fish, you just use the word fish.0614

But if I am talking about numerous types, you can say fishes.0617

Cartilaginous fishes, also known as class chondrichthyes, that would be the sharks and their relatives.0620

Like this, this is a ray, whether it is a stingray, manta ray, sharks, there is a lot of different species which are in the same group.0627

They have a cartilaginous skeleton not a hard bony skeleton, like we see in the bony fishes which is class osteichthyes.0636

There are two main varieties of bony fishes.0645

The ray fin fishes, here is an example here, the majority of fish that you have heard about.0647

If you have eaten fish, you have probably eaten ray fin fishes.0654

There are thousands of species, most fish are in that category.0658

You could see their fins have some of this.0662

But with a lobefinned fishes, their fins can take on this characteristic that are almost like early feet.0666

There is actually lot of false evidence that point to the first tetrapods, the first four-legged animals,0675

actually being related to lobefins fishes from hundreds millions of years ago.0680

Something about the bony connection between the main axis of their skeleton, the pelvic region, and those lobefins, 0686

something changed over time, we think to lead to actually having four legs, from these original lobefins from a long time ago.0698

One modern example of a lobefinned fish is the lungfish.0708

Coelacanth, here is a coelacanth, a drawing of one.0713

Scientist thought that they were extinct decades ago.0716

They existed for as far as we know, hundreds of millions of years.0720

But, they were discovered again, they are still around.0725

They have been around for a long time, they are kind of like this relic.0730

The modern day coelacanth look very similar to coelacanths from over a hundred of million years ago.0734

Amphibian characteristics, another class, class amphibian.0743

These are tetrapods as adults, meaning four legs or four feet.0747

They are four legged, tetra meaning four.0754

If you played the game tetris, you know all those pieces have four blocks.0757

I am not going to draw all of them but tetra pod, tetra meaning four.0763

There are some that do not have four legs, initially.0768

The majority of amphibians do not, as tadpoles.0773

That brings us to the name amphibian, what was that mean, where was that come from? 0776

Their name means dual life, if you look up amphi, it can mean both.0780

But in the context or connotation of what amphibian means, dual life is pointing to the fact that they start out their life in the water.0785

They have very different body structure that looks similar to a fish.0794

And then, they go through this change, they go through a metamorphosis.0797

If you have watched the insect part of lessons from before on animals,0802

metamorphosis is very common in various insects especially from caterpillar to butterfly, or to moth.0808

Metamorphosis also exists here, it is a change in their body structure.0814

They start out as a little tadpole with its long tail, gills, depending on the water.0819

Then they go through a change where the legs pop out, the gills fade away, 0827

they still depend on their skin, in terms of gas exchange, and they have tiny little lungs that develop.0832

The classic characteristics with amphibians, is its water and land dependency.0839

Some amphibian can, as adults, be very far away from water.0843

I will tell you more about toads later, but the majority of them still depend on water, as an adult.0847

When they have those tetrapod structures, when they have the 4 legs, they can walk around on land.0853

As I mentioned earlier, the skin is partly responsible for them having gas exchange,.0862

They have thin, moist skin, and it does assist in breathing.0867

They do have lungs, not nearly as big as the other terrestrial groups, which we will cover later in this lesson.0872

Circulation, they do have a double loop, unlike fish.0879

Their little heart which actually is three chambers.0883

Here is the two atria and the one ventricle at the bottom.0888

They have that three chamber heart, where actually some of the deoxygenated and oxygenated blood is mixed in the ventricle.0901

But they get by, it is efficient enough for them.0908

The double loop means that, they actually do have vessels going to their lungs and back to the heart to pick up oxygen.0910

And then, the heart sends that oxygenated blood to the body, and picks up CO₂,0916

bringing it back to the heart to go back to the lungs.0920

We will see that double loop in other animals, later on in this lesson.0923

Feeding, in terms of them getting energy as heterotrophs, they are mainly herbivores as larvae.0927

In terms of the tadpole here, the tadpole actually will eat a lot of plant material as little baby.0932

But then, when they grow up into this adult form, it is actually very common for this to be carnivorous 0948

or insectivores going after insects, etc.0956

Some frogs will even eat smaller frogs or toads will eat smaller frogs, it has been known to happen.0959

There are amphibians out there that do retain that herbivores nature as adults.0965

But, a lot of them end up being carnivores or insectivores as adults.0970

The cloaca, this is an exit hole that is not only for disposing of waste, but for reproduction.0975

It is kind of a multipurpose hole in their backside.0982

In terms of reproduction, it typically is external.0986

Both males and females are excreting sperm and egg out of that hole.0991

Nictitating membrane, that is on the eye, this covers the eye.0995

It is kind of like protective, in terms of preventing an eye from drying out.1003

It is also like permanent goggles, when they are in the water.1007

The nictitating membrane is unique to amphibians.1011

The tympanic membrane is actually an eardrum.1015

They do not have penne or auricles like other animals have.1018

They do have, it looks like a little helicopter pad or landing pad on their head, that has an eardrum.1022

They are sensitive to noise, a lot of frogs make mating calls, 1029

they need to be able to hear that, to hear members of their species.1036

They are arictothermic, cold-blooded, they are very sensitive to temperatures in the environment.1040

You will see frogs sunbathing to get warm.1043

If it is too hot, you will see them in the water or digging to get away from the heat.1047

External fertilization is typical with these, like I said earlier, males and females releasing sperm and egg into the water.1053

That is typically where they combine or the eggs will hatch to give rise to these tadpoles sooner around.1061

In the rainforest, especially, where it can be very moist in the air and there is a lot of rainfall and moisture,1067

frogs have been known to store their fertilized eggs on their back and carry them around.1072

There are exceptions into squirting sperm and egg in the water.1077

An interesting fact for the male frogs, by the way, a male frog does not have a penis.1081

It does not need one because they do not do internal fertilization with a cloracus.1085

They just need to have testes that make sperm and they release that sperm into the water.1090

And then, female frogs have ovaries and allow them to release their eggs into the water.1095

The amphibian order, when we look at class amphibian, there are few orders to keep in mind.1101

Order anura, frogs and toads, those classic amphibians we are used to seeing.1107

Some differences between frogs and toads, frogs typically have moister skin and thinner skin like these three frogs here.1111

That is actually a male frog on top of the female, they are probably getting ready to mate.1119

Actually, female frogs tend to be a bit bigger.1124

Toads tend to have thicker skin and less dependency on water.1127

Since, they have thicker rougher skin, they are not going to lose moisture as much into the air.1131

They do not dry out as much, typically.1137

Also, toads tend to have these bean shaped poisonous glands in the back of their head, 1139

that can release toxin as a defense mechanism.1145

There are frogs that can be toxic as well, especially brightly colored ones.1149

Order caudata is the salamanders and newts.1154

Here we have a salamander, a main difference between frogs and toads,1158

compared to salamanders and newts, as adults, salamanders retain their tail.1164

Unlike frogs, it disappears after their tadpole stage.1169

Also, the average salamander and nute tends to be much more long and skinny, in terms of its body style.1172

Difference between salamanders and newts, the average salamander,1180

though it is dependent on water because of its moist thin skin, 1184

it is different from the nute which will exclusively kind of stay in the water.1188

It will go out for breaths but newts spend a lot more time in H2O.1192

Order gymnofiona is the Sicilians.1199

Here is a Sicilian, it looks like a worm but they are not worms.1202

A lot of these actually have skin covering their eyes, and they will be blind, they cannot see.1206

But even though it looks like a worm, it is not.1213

It has a spine and it has other characteristics like a frog or salamander.1215

But of course, it does not have legs and these are some of the things that we are not used to seeing.1221

Based on morphological evidence, genetic evidence, this is technically an amphibian.1225

Reptiles, class reptilia, different from amphibians, they tend to have dry scaly skin.1233

They are not dependent on air passing through their skin for breathing, their lungs tend to be bigger 1239

and they use their lungs exclusively for getting gas in and out.1245

Molting occurs, meaning like an insect, if they want to grow in size, 1249

they have to shed that dried old skin layer, and they have a new layer underneath.1254

You may have heard snakes doing this, it is very common for reptiles to molt and leave behind their old skin.1260

Amniotic egg is also a step in terms of evolutionary change, when you compare reptiles and amphibians.1266

Amphibians have moist eggs that need to be in the water, or if they are outside the water, the air needs to be moist enough.1274

It is different with amniotic eggs that have this amnion inside.1281

They are for life entirely on land.1284

If you have ever seen a chicken egg, it is similar to reptilian egg because birds came from reptiles.1287

If you have ever seen a reptile egg in person, they have a hard shell just like a bird egg.1293

There are tiny little pores in the egg that does allow some gas exchange while they are developing.1298

But it is protective and it would not dry out as easily as amphibian eggs or fish eggs.1304

That is the major step, the majority of reptiles are on land.1309

There are some that do depend on aquatic environments but having their eggs in this way is definitely a help.1313

Like I mention earlier, lungs for gas exchange, these lungs are larger than the amphibian lungs.1320

Still, we see birds and mammals, the lungs will get a little bit different, as we go through this lesson.1327

Terrestrial, oceanic, aquatic, they are currently are no flying reptiles.1333

But back in the day, the pterodactyl did exist.1339

But terrestrial on land, oceanic, you do see some in the ocean.1343

It is not that common but there are some, and then aquatic, rivers, lakes, ponds, etc.1347

A three chambered heart is most common.1355

Some of them, you will have the two atria on top and a partial septum in this ventricle.1357

It is not completely enclosed.1365

However, with crocodiles, they do have a complete septum and that is not common for reptiles but good for crocodiles.1367

A three chambered heart is the most common, having that incomplete barrier between the sides of the ventricles.1380

They are mostly ectothermic, there are some reptiles like crocodiles that are bordering on being warm blooded.1387

Typically, they are considered cold blooded.1394

By the way, that term cold blooded is not the best term, in terms of what it means.1396

Some people think cold blooded means literally having cold blood.1402

What it is supposed to mean is that they are ectothermic, meaning they are dependent on the outer environment to warm their body.1405

You have probably seen reptiles like staying still so that they do not heat up very much.1413

Or they will sunbathe on an area when they want to warm up and get that sun absorbed.1419

The external environment has a big impact on their internal body temperature.1428

Most reptiles are carnivorous, actually eating live prey, killing live prey.1432

There are some out there that are herbivorous, a lot of turtles and tortoises having known to be herbivorous, and some lizards.1437

Being a carnivore is actually very common with reptiles.1447

Internal fertilization, this is a bit different than what we have seen.1452

With fishes and amphibians, external was common.1455

Actually male reptiles have a penis that comes out, when they are ready to mate,1459

and they do inseminate females internally, and then the eggs are laid externally, with the majority of them.1464

It is typical to have separate sexes.1471

When you look at fish and frogs, it has been known to happen where some fish and frogs1474

can change sex throughout their life, which is really fascinating that it can happen.1480

It has to do like hormonal changes, of course.1485

But, that is really not common with reptiles, I have not heard about that.1487

Separate sexes, having males and females is very common.1491

There is one snake that I have heard of, I believe it is a garter snake variety that actually can secrete pheronomes1497

to fool other males into having them think it is a female, and that is a strategy to help them during mating season.1505

You can look that up, it is very interesting.1514

It is typical for reptiles to have males and females that are separate.1516

Parthenogenesis has been known to happen in some.1521

This is when a female makes more females without males.1524

They do not need males, it has been known to happen, there have been cases.1532

In zoos for instance, where you have an alligator that has been isolated, never been around an alligator male, never, and it gives birth.1539

It is amazing that they can do that, they can just combine eggs inside of their ovaries and form offspring.1549

Some reptiles because of sex chromosome differences will be able to have males, when they do that.1556

They will be different, if it is going to occur in a human female, she would only be able to make new females.1563

But, because of its sex chromosomes differences that is kind of interesting.1571

Scientists are not sure if they can like will it to happen or it just tends to happen when males are not around.1575

It is one of those mysteries that is not completely known, in terms of the specific answers yet.1582

Reptile orders, when we look at class reptilian, there are few orders.1589

Order squamata, that would be the snakes and lizards, there is a snake.1593

I’m sure that you are aware of this, that snakes do not have legs.1597

Some of them do have remnants inside their body and there is more fossil evidence for this, 1601

that they were originally from tetrapod ancestors, that they gradually lost their legs, in terms of the size gradually getting reduced.1607

As you can tell by looking at them, they get along just fine slithering.1617

They are very sensitive to vibrations on the ground because of that lifestyle.1621

The other thing that helps them is what are called jacobson's organs.1625

With snakes, it is very common for them to flick their tongue.1628

It is like their tasting the air, in a sense, because they will take odor molecules.1633

Odor into molecules from the air, bring their tongue back in 1637

and have those little odor molecules go into the jacobson’s organ which is like another smelling ability.1640

If it was not for Jacobson’s organs, it would be a lot harder for them to track down prey.1647

Order crocodilian, that includes the crocs and alligators, checked it out, there it is.1652

This is an example of one that can be aquatic and they do move around on land, 1657

but these are more comfortable in the water.1662

They do have to breathe air because they have lungs, they are not breathing with the skin, not breathing with gills.1666

They have to do come up for a buff, like this one is doing.1670

Order testudinata, that would be the turtles and tortoises.1674

If you are wondering, what is the difference between turtle and tortoise, in general tortoises, cannot be in water.1677

They are built for land.1682

You can imagine, if you threw this little guy in the water that would be very cool but it would not be able to swim.1684

You can tell by its body style and just how big this shell is, that they are probably pretty heavy and not to be able to swim.1690

There are turtles out there, like sea turtles, many different species of those, that are adapted for life in the water.1698

Their legs look more like thin shaped, like a flipper.1704

Order sphenodontia, that is the tuatara, there is a tuatar, they are cute.1709

These had been known to live a long time, we are talking like 800 years which is pretty amazing.1714

There you have the reptilian orders, the major ones.1721

Bird characteristics, here we go class avis.1725

That word avis comes from a Latin for in the air, like there are Spanish words like avion means an airplane.1728

Avis meaning flying.1737

8,600 species, that is the most diverse land class of vertebrates.1740

You will see that with mammals, they come close.1746

There are a lot of bird species, a lot of variety.1750

They are evolved from reptiles, you can look at them in and see some remnants of that.1753

There are obvious differences with birds and reptiles.1758

They diverged around hundreds of millions years ago, they still have these amniotic eggs that are quite similar.1761

Scales, if you look at their feet especially chicken feet.1769

You look closely, they have those little claws or talons, and they have scaly feet, it is a remnant from where they came from.1772

The feathers are definitely unique characteristic, those assist with flight.1782

The theory is that, they originally occurred in a group of dinosaurs, a little over hundred million years ago.1785

They would have been some other benefits initially, because is not like the feathers appeared and they can fly.1793

The bone density was not there yet, the articulation with the bony parts was not there yet.1799

Maybe, they initially helped with display like attracting mates or helping steer themselves quickly,1803

as they are running through the forest or something like that.1809

Eventually, the feathers definitely assist with the ability to fly.1813

When you look at the different feather types, the main kinds are the contour feathers which you tend to see on the outside.1817

They have barbs and scales that are like interwoven.1823

Sometimes, those break, they can go back together like a zipper.1827

Like if you re-zip the sides of a zipper, the parts of the feathers can actually realign and reconnect.1832

That is one of the cool things about these contour feathers.1838

If they have little breaks on those, they can repair them.1841

When they preen, it is what a lot of birds do, when it look like they are biting themselves1844

or doing something with their feathers, that is what they are doing.1850

The down feathers tend to be deeper and they are softer, they are much softer than the contour feathers around the outside.1853

That is why a lot of comforters and pillows have these down feathers inside of them, they are very soft.1859

If you are wondering, what is the purpose of the down feathers? 1865

Insulation, they can help trap air and help with temperature control in the bird’s body.1867

A lot of birds have these preen glands, where they will go back and takes some oily substance 1873

from these preen glands and spread it all over their feathers.1878

That oily substance is protective and waterproofing.1881

It is going to be really common with birds, like ducks, that do swim and they are found in the water.1885

Lightweight bones, part of flying is having bones that are less dense.1893

They have this like of honeycomb bone structure, when you look inside of them.1898

They are not quite as filled in or dense as reptilian bones, or the average mammalian bones.1902

They do have this fused collarbone in sternum area.1908

If you have ever seen the wishbone, that is what I am referring to.1911

That wishbone, you can find, if you are eating turkey or chicken, it is a modified part of that.1915

This part of their skeleton is different than other vertebrates.1921

It actually helps with the flying ability and attaching their extensive chest muscles.1925

And if you ever eaten a chicken breasts, a significant size,1932

those chest muscles have to do with flight and the ability to power through, and actually fly with a lot of birds.1935

Lungs with air sacs, like reptiles, they have lungs, they have to breathe air.1944

These air sacs bring air in, when they breathe, and then the air sacs fill air into the lungs.1949

That is how they get oxygen in their body and CO₂ out.1956

Four chambered heart here, compared to the average reptile, there is a difference.1959

Up at the top two atria, each one is an atrium, and at the bottom two ventricles.1966

No teeth, that is a major change from reptiles.1979

If you look at some transitional fossils from around a hundred of million years ago,1982

something like an archeopteryx, look this up, it is pretty interesting.1986

It has part of its body that are still very reptilian and parts that are very birdlike, 1994

especially the feathers but this actually still retains some teeth.1999

Birds now do not have teeth, some of them have very sharp beaks.2004

They can have like serrated edges but no teeth.2008

In terms of them digesting, they would have a crop and a gizzard.2011

A crop is kind of like an earlier stomach that will hold food and the gizzard helps break it down,2016

as it then goes through the intestinal area.2023

They are endothermic, they are warm blooded like mammals.2026

They have the ability of temperature control.2028

Considering that you can find birds in the arctic and antarctic,2031

it makes sense that they can deal with that extreme cold temperature because they are warm blooded or endothermic.2035

Internal fertilization, like reptiles, they do have to have internal fertilization with sperm go inside the female, and then eggs are laid.2043

Bird order, this is most of them.2055

I do not have all of them because there are a lot but these are some major ones.2058

Class avis has several orders, order passeriformes, jays, finches, crows.2062

I have this dotted with exclamation point because there is more than that.2074

Most birds that you familiar with, that you see flying around would be in this group.2078

There are a lot, it is a very abundant order.2083

Order ciconiiformes, hens, flamingos, storks, and vultures, are in that particular group.2087

Order sphenisciformes, penguins.2095

All those are penguins that you are used to seeing, like from the movie happy feet, or nature documentaries.2097

The biggest one of them would be the emperor penguin, quite tall, 2105

and they do have modified wings that look like flippers because they are swimming.2109

They have lost their ability to fly, but it is alright, they are like little bullets in the water when they go after fish.2114

Order strigiformes, that would be the owls like this right here, it looks sleepy.2119

Order struthioniformes, the flightless birds like this emu, that would also include the kiwi, 2125

the ostrich, and some that are actually not extinct.2131

Order anseriformes, swans, geese, and ducks.2135

Those are your major bird orders, and examples of what kind of birds are inside of them.2139

Thank you for watching