1.
The Vertebrates

2.
• The vertebrates are a sub-group of the
phylum chordata, creatures with a notochord
• In vertebrates the notochord disappears as
the organism develops and is replaced by a
backbone or spine.
Phylum Chordata
Subphylum Vertebrata

3.
Features of Vertebrates
• Internal skeleton, composed of cartilage
and/or bone.
• A vertebral column (or spine) of vertebrae
made of bone and/or cartilage.
• A cranium or skull that protects the brain
– In addition most vertebrates have
• Pharyngeal pouches at some stage of life
• A post-anal tail (a posterior tail above or behind anus)
• A notochord that disappears as the spine grows

4.
The main Classes of Vertebrates
• Agnatha: the jawless fish (lampreys, hagfish)
• Chondrichthyes: cartilage fish (sharks, rays)
• Osteichthyes: the boney fish (most fish)
• Amphibia: amphibians (frogs, salamanders)
• Reptilia: the reptiles (lizards, snakes, crocodiles)
• Aves: the birds (penguins, robins, ostriches)
• Mammalia: the mammals (cats, mice, humans)

5.
Early Evolution of Vertebrates
• Some biologists think vertebrates first evolved
about 550 million years ago, however the oldest
fossils date to the Ordovician period (440-510 MYA)
• The earliest fossils are of jawless fish, similar to
class Agnatha. (probably evolved from ancestors of lancelets)
• About 440 million years ago (Silurian or late
Ordovician period), jaws evolved from gill arches.
• About 370 million years ago (Devonian period)
some lobe-finned fish moved inland and evolved
into amphibians
• By 300 million years ago reptiles had appeared
• The earliest mammals appeared about 200 million
years ago
• Birds are the most recent vertebrates, with fossils
dating back about 150 million years.

6.
Geological Timescale
Paleozoic Mesozoic Cenozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ternary
Quaternary
265144206245290363409439510543
Jawless Fish
Cartilage Fish
Boney Fish
Amphibians
Reptiles
Mammals
Birds
Synapsids
Dinosaurs

7.
Systems
• All vertebrates have well developed organ
systems, including:
– Internal skeletal system (endoskeleton)
– Integument, or body covering that may include
skin, scales, feathers or hair.
– Muscles capable of rapid movement
– Respiratory system with gills or lungs
– A closed circulatory system with multi-
chambered heart.
– A two-ended digestive system
– A brain and well developed nervous system

8.
The fish used to be placed in the now-defunct Class
Pisces, but this class was later split into the three
more modern classes. Now the term fish is an
informal term for any members of these three classes
The Fishes
• “Fish” is a non-scientific name that is used
to refer to three different classes of
vertebrate.
– Class Agnatha (jawless fish)
– Class Chondrichthyes (cartilage fish)
– Class Osteichthyes (bony fish)

9.
Geological Timescale
Paleozoic Mesozoic Cenozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ternary
Quaternary
265144206245290363409439510543
JawlessFish
Cartilagefish:“sharks”
Osteichthyes
Lancelets

10.
Agnatha: the Jawless Fish
• These fish have eel-like bodies, with no
jaws and no paired fins. Their skeletons
are cartilage. There are two main types:
– Lampreys: parasites on other fish
– Hagfish: bottom-feeders
Mouth of a lamprey
adult lamprey
Hagfish

11.
Chondrichthyes: Cartilage fish
• These fish have jaws, but their skeletons
are made of cartilage. They do have
paired fins, but arranged differently than
the more common bony fish. There are
three main types:
– Sharks
– Rays
– Skates

12.
Sharks
Gill slits Pectoral fins
(paired)
Pelvic fins
(paired)
Anal fin
Jaws
Anterior dorsal fin
Caudal
(tail) fin
Also see the diagram on page 805 of your text book

13.
Skates and Rays
• Skates and rays have flattened bodies, with
extended, wing-like fins. In manta rays, the
pectoral fins have become “horns” below the
mouth.
Skate Ray
Pectoral fins
Pelvic fins

14.
Osteichthyes: The boney fish
• These fish have skeletons that contain at
least some true bone.
• Parts of the skeleton may still be made of
cartilage or softer, less calcified bones
than found in other vertebrates.
Most familiar fish are osteichthyes (and so are a few strange ones)

15.
Features of Osteichthyes
• Gills covered by an operculum
• Bones
• Paired fins
• Lateral line sense organs

16.
Parts of a fish
Lateral Line
Operculum
Pectoral fin
Pelvic fin
Anterior dorsal fin
Posterior dorsal fin
Anal fin
Caudal fin
Eye

17.
Enrichment: Some Strange Fish
The Sea horse doesn’t even look like a fish. It’s
orientation is all wrong and it’s fins and tail are highly
modified. The males carry the young. But it is a true fish
anyways.
The coelacanth was thought to
have been extinct for 60 million
years, until a fisherman caught one
off the coast of South Africa. It is a
lobe-finned fish. 
 The lungfish is able to crawl short distances across land on
its lobed fins, and can breath air. They are found in Africa,
South America and Australia
The Angler fish dangles a bit of
glowing bait in front of its face to
attract prey, which it then grabs and
swallows with its large mouth. 

18.
Enrichment:
Not a fish!
Whales and dolphins look like fish, but
they are actually mammals.
Jellyfish, starfish, silverfish, crayfish may
have the word fish in their name, but they
are not true fish.
Jellyfish = Cnidaria
Starfish = Echinoderm
Silverfish = Insect
Crayfish = Crustacean
the prehistoric Ichthyosaur (below)
was actually a reptile.

19.
Clown Fish

20.
Class Amphibia
“The Amphibians”

21.
Amphibians
• Features of modern amphibians
– Moist, thin skin with no scales
– Feet (if present) have no claws, often webbed
– Respiration is through a combination of gills,
skin and lungs
– Eggs lack shell or membranes. Fertilized
externally. Dry out unless protected.
– Most have larval and adult stage, and must
undergo metamorphosis

22.
Orders of Amphibians
• Kingdom Animalia, Phylum Chordata,
Class Amphibia,
– Order Anura: Frogs and Toads
– Order Urodela: Salamanders, Newts
– Order Apoda: Caecilians, legless amphibians

23.
• Amphibians first appeared about 370
million years ago. They probably evolved
from lobe-finned fish that came on to land
to crawl from pond to pond.
Ichthyostega (prehistoric amphibian)
Frogs and
salamanders

24.
Geological Timescale
Paleozoic Mesozoic Cenozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ternary
Quaternary
265144206245290363409439510543
FirstAmphibians
Apoda (Caecilians)
Fish
Lobe-finned fish
Urodela (salamanders)
Anura (Frogs)
Ichthyostega Salamander Frog
Amphibians
Amphibians
Diversify
Caecilian

25.
Frog (a sample amphibian)
Like most amphibians the frog has a moist skin. The
skeleton and internal organs are similar to those in most
“higher” vertebrates. The frog must return to water in
order to reproduce (its eggs would dry out on land). Frogs
undergo a metamorphosis from a fish-like tadpole into
the adult frog.

26.
Metamorphosis
• Most amphibians have a larval
form and an adult form.
– The larva’s respiration is
generally through external gills
– The adult’s respiration is through
a combination of lungs and skin
breathing.
Axolotl,
a salamander larva
Tadpole, a frog larva

27.
Amphibian Facts
• The largest amphibian
is the Chinese giant
salamander
• The smallest amphibian
is the Brazilian gold frog
• The most poisonous
amphibians (some would
say the most toxic animals in
the world) are the three
varieties of dart-poison
frogs (AKA poison
arrow frogs)

28.
Assignment
• Skim through chapter 42
– Note the diagrams of internal frog systems
• Read page 833
• Answer the following questions
– 1. When, and from what ancestor, did the earliest
amphibians evolve?
– 2. describe the main differences between the orders
of amphibians.
– 3. Why do most amphibians require a body of water in
order to reproduce?
– 4. Describe the life cycle of a frog.
Amphibians evolved about 370 million years ago. They probably
evolved from a lobe-finned fish similar to modern lungfish.
The Anura have large legs, especially hind legs for jumping. Urodela
(salamanders) have smaller legs, Apoda (ceacilians) have no legs.
They require a wet area for mating, also their eggs would dry out on
land unless protected.

29.
Frogs hatch from small gelatinous eggs (AKA. Spawn) in the form of
tadpoles. As the tadpole grows it develops legs and its tail resorbs
(gradually disappears) until the adult has the familiar frog shape

30.
ClassReptilia
“TheReptiles”

31.
Evolution of the Reptiles
• Reptiles appeared more than 300 million
years ago.
• They flourished during the Mesozoic era
(245 million to 65 million years ago), so
this time period is called “the age of
reptiles”
• 65 million years ago, many species
became extinct. Only four orders of
reptiles survived to modern times.

32.
Geological Timescale
Paleozoic Mesozoic Cenozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ternary
Quaternary
265144206245290363409439510543
FirstReptiles
Age of Reptiles
Birds
Mammals
Snakes & Lizards
Crocodilians
Turtles
Synapsids / Therapsids
Dinosaurs (& related orders)
Reptilesdiversify
ReptilesAmphibians
Tuataras
Extinction

33.
Reptile Evolution
mammals
Turtles
Lizards
Snakes
Tuataras Crocodiles
Birds
DinosaursPrimitive Reptiles
Ichthyostega
frogs
Mesozoic
Age of
Reptiles 1
2
3
4
5
6 7
8
9
10
11 12

34.
Features of Modern Reptiles
• Modern reptiles have:
– Waterproof skin, usually covered in scales
– Feet (if present) have claws
– A three or four chambered heart*
– Ectothermic body temperature regulation. (ie.
“cold-blooded”)
– Well developed lungs, eliminating the need for
gills or skin breathing**
– Amniotic eggs (have a shell or protective
membrane, and are fertilized internally.)
*four chambered in crocodilians, three chambered in all other reptiles.
**some snakes have limited skin-breathing ability.

35.
Surviving Orders of Reptiles
• Kingdom Animalia, Phylum Chordata,
Class Reptilia*
– Order Chelonia: Turtles and Tortoises
– Order Crocodilia: Crocodiles, alligator, caiman
– Order Squamata:
• Suborder Lacertilia: Lizards
• Suborder Serpentes: Snakes
– Order Rhynchocephalia: Tuataras
*recently some taxonomists have suggested replacing “Reptilia” with
“Sauropsida” but we will continue to use the more traditional name.

36.
Turtle crocodile
Lizard and snake
Tuatara

37.
The Amniotic Egg
Secret to the Reptile’s Success
Unlike the eggs of
amphibians and fish, the
amniotic egg of reptiles,
birds and monotremes is
internally fertilized (through
sexual contact) and has a
protective outer membrane
or shell that prevents it
drying out.
It contains enough nutrients
in the yolk to nourish the
embryo.
The allantois is a sac that
holds wastes until the
embryo hatches, and also
provides some oxygen.
The amniotic egg freed the reptiles of the need to
return to the water to reproduce.

38.
Evolution of the heart
As reptiles evolved, so did their hearts. Early reptiles had a 3 chambered
heart, just like the amphibians.
As they became more active, a “septum” began to appear in their hearts.
At first the septum served little purpose, but slowly it became an advantage..
The septum prevented oxygen-rich blood from mixing as much with the
oxygen poor blood. This allowed a higher activity level for the reptiles
The septum evolved to divide more and more of the heart. Most reptiles
today have a fairly significant septum.
In a few reptiles, like crocodiles, the septum completely divided the heart
This four chambered heart
was passed on to the most
successful descendants of
the reptiles, the birds and
mammals.

39.
Reptile Facts
• Smallest reptile is the
Jaragua Sphaero a dwarf
gecko
• The largest (living) reptile is
the salt water crocodile.
• Tuataras have a tiny “third
eye” on the top of their heads,
related to a human’s pineal
gland.

40.
Assignments
• Skim pages 839-854, Read page 855
• Copy the phylogenic tree from p. 841
• Draw & label a diagram of the Amniotic
egg, from page 843. List the features of
the amniotic egg.
• Draw a diagram of the heart of a typical
reptile (p.846)
• List the distinguishing features of each of
the four surviving orders of reptiles.

41.
Class Aves
The Birds

42.
• The earliest accepted fossils of birds date back
to 150 million years ago.
– Recent finds of dinosaur fossils with feather-like
scales suggest an earlier evolution of birds, but this is
still debated.
• Archaeopteryx lithographica is the oldest
confirmed bird species.
– It had several reptilian features, including claws on its
wings, teeth and a long bony tail.
– See page 863 for a drawing of Archaeopteryx
Evolution of the Birds

43.
Geological Timescale (Birds)
Paleozoic Mesozoic Cenozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ternary
Quaternary
265144206245290363409439510543
Feathered
dinosaurs
Dinosaurs
Birds
Archeopteryx

44.
Features of Modern BirdsFeatures of Modern Birds
 Skin covered in feathersSkin covered in feathers
 Wings in place of the forelimbsWings in place of the forelimbs
 Light-weight rigid skeletonLight-weight rigid skeleton
– Many of the bones are hollow to reduce weightMany of the bones are hollow to reduce weight
 Endothermic metabolism (“warm blood”)Endothermic metabolism (“warm blood”)
– Birds maintain a high body temperature (40Birds maintain a high body temperature (40°°-41-41°°C)C)
 Unique respiratory systemUnique respiratory system
 A beak in place of teethA beak in place of teeth
 Amniotic eggs with hard shellsAmniotic eggs with hard shells

45.
Bird’s Respiratory System
Birds have many sacs attached to their lungs.
As they inhale, air passes through the lungs and fills the sacs.
As they exhale, the air passes through the lungs again.
Essentially they pass twice as much air through the lungs with
each breath.
Lungs
Air Sacs

46.
Flight
• Over 90% of all birds are able
to fly.
• Flight has been made
possible by many
adaptations:
– Wings with an “airfoil” shape.
– “Keel” shaped breast bone with
attachment points for large
muscles that operate the wings.
– Hollow bones to reduce weight
– Feathers insulate and propel.
• Down feathers for insulation
• Contour feathers give birds shape
• Flight feathers give propulsion

47.
Diversity in Birds
• There are 29 different orders of birds
– Only the twelve most common are described in the
textbook
– The smallest bird is a Cuban hummingbird not much
larger than a bumblebee (5 cm long including tail,
about 1/20 ounce or just over 1 gram)
– The largest bird is an African ostrich (9 ft tall, 350 lb,
or 2.7m, 160 kg) It is flightless, but a good runner.
– Penguins are the fastest swimming birds (Penguins are
also flightless, the BBC video that showed flying penguins was an
expensive Computer Generated April fool’s joke)

48.
A Few Orders of Birds
• Falconiformes: Birds of prey,
or “raptors”
• Anserformes: Ducks and
Geese
• Strigiformes: Owls
• Passeriformes: Songbirds
• And there are 25 more orders…

49.
Assignments
• Skim through pages 861-874 of the text.
• Carefully read page 875
• Create a brief set of notes (about one
page) that summarizes the main things
you have learned about birds
– be prepared to show your summary to me in the next class
• Answer questions 16 to 22 on page 876

50.
The Mammals

51.
Origin of Mammals
• Mammals probably evolved from the
synapsids, an early reptile family that
included Dimetrodon,
• The Therapsids, like this Lycaenops were
a later type of synapsid that looked more
mammal-like
• The first true mammals that appeared
about 150 million years ago were small,
shrew-like organisms

52.
Geological Timescale (Mammals)
Paleozoic Mesozoic Cenozoic
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
Permian
Triassic
Jurassic
Cretaceous
Ternary
Quaternary
265144206245290363409439510543
Synapsids  Therapsids
150MYA
Age of Mammals
Mammals
Extinction

53.
Characteristics of Mammals
• Endothermy (warm-blooded)
• Skin covered in hair or fur
• In whales and humans the hair is reduced to small patches
• Four chamber heart,
• with fully divided ventricle and separate circulation
• Mammary glands
• Mammals secrete milk to help nourish their young
• Single jawbone
• Reptiles have a split lower jaw, mammals have a fused one.
• Specialized teeth
• Whereas reptile teeth are all similarly pointed, mammals can have
different shapes (molars, canines, bicuspids etc.)
• Diaphragm: a specialized muscle that makes breathing more efficient

54.
Three Subclasses of Mammals
• the Monotremes (Prototheria) 0.2%
– The monotremes are egg-laying mammals
(1 order with 3 species)
• The Marsupials (Metatheria) 5.8%
– Marsupials give birth to immature offspring, and
then carry them in pouches. (1 order, 334 species)
• The Placental Mammals (Eutheria) 94%
– Placental mammals give birth to well developed
offspring after a longer gestation period. (18 orders,
over 5400 species)

55.
The Monotremes
Kingdom Animalia, Phylum Chordata, Class Mamalia, (Subclass Prototheria)
• Order Monotremata: (only 3 species exist)
• “Duck-billed” Platypus
• “Short-beaked” Echidna
• “Long-beaked” Echidna (aka. “Spiny Anteater”)
• Monotremes lay eggs, but they nurture
their young with secretions from nippleless
mammary glands.

56.
The Marsupials
• Subclass Marsupialia: (about 280 species
in 8 orders)
– Including:
• Kangaroo
• Wallaby
• Tasmanian Devil
• Tasmanian wolf (believed extinct)
• Marsupial mole
• Koala
• Wombat
• Opossum (only native marsupial in North America)

57.
Interesting facts about
marsupials
• Most female marsupials have 2
vaginas within a single cloaca
• Most male marsupials have a forked
penis
• Marsupials have a gestation period of
less than 5 weeks (some of them much less).
• Kangaroos don’t fart, (or more accurately,
they produce no methane gas from their digestion)
• A baby kangaroo is about an inch long
when born. It crawls to its mother’s
pouch and stays there for about 9
months.

58.
Placental Mammals
• Can produce a placenta.
• Give birth to well-developed
offspring.
– In fact, some species offspring can
be standing and running minutes
after being born.
• Have longer gestation periods
than marsupials.
For your information only.
Don’t try to memorize!

59.
Main Orders of Placental Mammals
(about 5500 species in )
• Order Rodentia: mice, rats, squirrels, porcupines, beaver
• Order Edentata: ant-eaters, sloths, armadillos
• Order Lagomorpha: rabbits, hares, pikas
• Order Insectivora: shrews, moles, hedgehogs
• Order Primates: monkeys, lemurs, apes, humans
• Order Chiroptera: bats
• Order Carnivora: dogs, cats, bears, seals, sealions
• Order Artiodactyla: ungulates, deer, cows, pigs, camels
• Order Perissodactyla: horses, zebra, rhinoceros, tapirs
• Order Cetacea: whales, dolphins, porpoises, orcas
• Order Sirenia: manatees and dugongs
• Order Proboscidea: elephants, mammoths (extinct)
While I don’t expect you to memorize all
these orders of mammals, I do give them
as examples of the diversity of the class.
The five in bold print are of particular
interest, because they clearly illustrate how
different mammals can be.
You should be aware of them, as well as
any other orders that interest you.

60.
Mammals: Assignments
• Read:
– Pages 881 to 896
• In your notebook:
– List the organs and systems found in most mammals.
The drawing on page 885 may help you list some of
the organs
– Copy the phylogenetic tree from page 891 (just the
names, not the pictures)
• In your assignments book:
– Do questions 6 to 20

61.
Comparison of Vertebrates
Class Heart
chambers
blood limbs covering
Agnatha (jawless fish) 2 Ectotherm
(cold)
None Skin/
scales
Chondrichthyes (shark) 2 Ectotherm
(cold)
Fins Plaquoid
scales
Osteichthyes (fish) 2 Ectotherm
(cold)
Fins Wet skin
and/or scales
Amphibia 2, 3 Ectotherm
(cold)
No
claws
Moist skin
Reptilia 3, 4 Ectotherm
(cold)
Claws
(except snakes)
Dry skin
and/or scales
Aves 4 Endotherm
(warm)
Wings
Claws
Skin and
Feathers
Mammalia 4 Endotherm
(warm)
varies Skin and
hair / fur

62.
Mammal Organ Systems
• All vertebrates have well developed organ
systems, but those of mammals are among the
best developed.
• Organ systems include:
– Integumentary system (skin, with hair or fur)
– Muscular system (muscles– skeletal, cardiac, smooth)
– Skeletal system (bones, cartilage, connective tissues)
– Digestive system (esophagus, stomach, intestines etc.)
– Cardiovascular or circulatory system (heart, blood
vessels)
– Lymphatic and Immune systems (nodes, vessels)
– Respiratory system (fully developed lungs, trachea)
– Excretory or Urinary system (kidneys, bladder)
– Reproductive system (most species have a uterus)
– Endocrine system (glands)
– Nervous system (brain, dorsal spinal cord)

63.
How a Mammal is Organized
• Levels of organization:
Cells tissues organs organ-systems
Many similar cells working together form a tissue
Several tissues working together form an organ
Several organs working together form a system

64.
Major Tissue Types
• The four major tissue types are:
– Muscle tissues: movement
– Nervous tissue: communication
– Epithelial tissue: covering organs and surfaces
– Connective tissue: connecting and supporting.
• Each tissue type has several sub-types:
– for example, muscle tissue could be skeletal
muscle, cardiac muscle or smooth muscle
tissue.

65.
Body Cavities
• Body cavities are compartments within the body
that house organs.
• Humans, like most mammals have four main
body cavities:
– Cranial Cavity: Holds the brain
– Spinal Cavity: Surrounds the spinal cord
– Thoracic Cavity: Contains the heart, esophagus,
lungs, and other respiratory organs
– Abdominal Cavity: Contains the organs of the
digestive, reproductive and excretory systems

66.
• The cranial and spinal
cavities are often
referred to as dorsal
cavities because they
are mainly at the back
of the body.
• The thoracic and
abdominal cavities are
the ventral cavities
because they are on
the front or stomach
side of the body.
• Sometimes the lower
portion of the
abdominal cavity is
called the pelvic
cavity.
diaphragm

67.
Systems
• You have learned about the organ
systems in past courses, so we will do just
a quick review of a few of the systems
here.