Chordates
Characteristics common to ALL
chordates
Dorsal nerve cord
 Pharyngeal slits
 Notochord
 Tail

Dorsal nerve cord
Pharyngeal Slits

The wall of the pharynx is perforated by
up to 200 vertical slits, which are
separated by stiffening rods.
Jawless to Jaw
Used to collect food in an aquatic
environment
Notochord

a flexible, rod-shaped body found in
embryos of all chordates

In lower vertebrates, it persists
throughout life as the main axial support
of the body, while in higher vertebrates it
is replaced by the vertebral column.
Tail
Some animals lose tail during
development
Nonvertebrate chordates and
Vertebrates
Nonvertebrate chordates have a notochord
(analogous to spinal chord) but lack a
bony covering- the vertebrae
 Vertebrates have a spinal chord protected
by bones

Principle Chordate Features
13
The Nonvertebrate Chordates

Tunicates (sea squirts)
– exhibit neither a major body cavity nor visible
segmentation
 tadpole larva clearly exhibits all basic
characteristics of a chordate
 adults exist as sessile filter-feeders
14
Tunicates
15
The Nonvertebrate Chordates

Lancelets
– scaleless, fishlike marine chordates
 notochord runs entire length of dorsal nerve cord
 feed on microscopic plankton using cilia-generated
current
16
17
Characteristics of Vertebrates
Vertebral column
 Endoskeleton
 Distinct, well-differentiated head with
cranium
 Closed circulatory system with chambered
heart
 RBC’s with hemoglobin

18
Overview of the Evolution of
Vertebrates

Main CLASSES
– Fishes – cartilaginous and bony
– Amphibia - amphibians
– Reptilia - reptiles
– Aves - birds
– Mammalia - mammals
19
Fishes
Over half of all vertebrates are fishes.
 Characteristics (generally)

– jaws and paired appendages (except lampreys and
hagfish)
– scales
– fins
– gills
– single-loop blood circulation
– Heart with 2 chambers (1 atrium, 1 ventricle)
– Lateral line system
20
History of the Fishes

Rise of active swimmers
– Sharks and bony fishes replaced primitive
fishes due to a superior swimming design.
 caudal (tail) fin
 dorsal (stabilizing) fins
 pectoral (shoulder - elevator) fins
 pelvic (hip- elevator) fins
21
Hagfish
22
23
Lamprey
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History of the Fishes

Sharks become top predators
– Jaws with multiple rows of teeth
– Paired pectoral and pelvic fins
– Buoyancy from storing oil
– extremely advanced reproduction
 shark eggs fertilized internally
 Most give birth to live young
25
Hammerhead Shark
26
Elephant Fish
27
Whale Shark
28
Tooth from Megalodon (left),
and Great White
29
History of the Fishes

Bony fishes dominate the water
– Skeleton composed of bone
– Swim bladder for bouyancy
– Gills protected by operculum
– highly mobile fins, thin scales, and completely
symmetrical tails
– Most have external fertilization and external
development
30
Angler Fish
31
Deep Sea Angler Fish
32
Flounder
33
34
Electric Eel
35
Sea horse and Sea dragon
36
Another Sea dragon
37
Mola mola or Ocean sunfish
38
39
Coelacanth
40
Coelacanth fossils
41
Living Coelacanth
42
Shark
Dissection
Following is a series of video clips of
dissection of various shark species.
This will give you some idea of what
you will encounter with our shark
lab
Lobe-Finned Fish and Primitive
Amphibians
44
Amphibians
Live on both land and in water (“double
life”)
 Characteristics

– legs
– cutaneous respiration, lungs, gills
– Heart with 3 chambers (double loop circulation)
 Pulmonary
 Systemic
– External fertilization and development in nearly
all
45
History of the Amphibians

Adaptations for the invasion of land
– legs to support body’s weight
– lung to extract oxygen from the air
– redesigned heart to drive new respiratory
system
– reproduction in water to prevent egg
desiccation
– system to prevent body desiccation
46
History of the Amphibians

Amphibians today
– Anura - amphibians without tails
– most live in or near water, and return to water
to reproduce
 eggs fertilized externally and hatch into tadpoles
– metamorphosis
47
Poison dart frogs
48
Proboscis frog
49
African goliath frog
50
Jabba the Frog
51
Flying Frog
52
Chinese fire-bellied toad (most
venomous)
53
History of the Amphibians
– Urodela (Caudata) - salamanders
 have elongated bodies, long tails, and sooth, moist
skin
– fertilization is usually external
54
World’s largest salamander
55
Spotted salamander
56
Rodent surprise for lunch!
57
History of the Amphibians
– Apoda
 caecilians - highly specialized group of tropical
burrowing amphibians
– legless, but have jaws and teeth
– internal fertilization
58
Caecilian
59
Reptiles

Characteristics
– amniotic egg
 chorion - outermost membrane
 amnion - encases embryo
 yolk sac - surrounds yolk (food)
 allantois - surrounds waste cavity
– dry skin with scales
– Internal fertilization; usually external
development
60
Baby komodo dragon
61
allantois
airspace
eggshell
embryo
albumen
amnion
chorion
Yolk
sac
62
Rise and Fall of Dominant
Reptiles
 Dinosaurs: learning
to run
– body located directly over legs
 increased speed and agility
63
Apatosaurus
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Triceratops
65
Diplodocus
66
Stegosaurus
67
Velociraptor
68
Another reconstruction of
Velociraptor
69
Some pterosaurs were the size of
small airplanes
70
71
Plesiosaurs were aquatic
72
Japanese fisherman caught this
creature in 1977
73
Today’s Reptiles

Of the 16 orders of reptiles that have
existed, only 4 survive
– turtles
– lizards and snakes
– tuataras
– crocodiles
74
Rise and Fall of Dominant
 Other important Reptiles
characteristics
– internal fertilization
– improved circulatory system
– ectothermic - heat obtained from external sources
– endothermic - generate own heat
75
Gaping is a means of cooling
the blood
76
Living Reptiles

Order Chelonia: turtles and tortoises
– differ from other reptiles because their bodies
are encased within a protective shell
77
Some tortoises have lived to
150 years
78
Green sea turtle
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Pacific leatherback sea turtle
80
Rise and Fall of Dominant
Reptiles
 Order Rhynchocephalia:
tuatara
– lizardlike animals about half a meter long
– contain parietal eye
– only found on island off New Zealand coast
81
82
Rise and Fall of Dominant
 Order Squamata:Reptiles
lizards and snakes
– three suborders
 Sauria - lizards
 Amphisbaenia - worm lizards
 Serpentes - snakes
– paired copulatory organ in males
– lower jaw not joined directly to skull
83
The chameleon is a lizard
84
Jackson’s chameleon
85
86
Gecko
87
Gila monster (venomous)
88
Skinks are sometimes called
worm lizards
89
Blue-tongued skink
90
World’s smallest skink
91
Rainbow boa constrictor
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93
Scarlet king snake
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Coral snake
95
King or Coral?
96
Copperhead
97
Sidewinder rattlesnake
98
Rattlesnake victim
99
Rise and Fall of Dominant
 Order Crocodilia:Reptiles
crocodiles and alligators
– remained relatively unchanged
 only two species of alligators
– southern US and China
– resemble birds more than other living reptiles
(care for young and four-chambered heart)
100
Nile crocodile
101
Caimans live in South America
102
Gharial
103
104
Birds

Class Aves contains 28 orders containing
166 families and about 8,600 species.
– key characteristics
 feathers
– modified reptilian scales ?
 flight skeleton
– thin, hollow bones
105
History of the Birds
– Archaeopteryx (similar to modern Hoatzin)
– Aves listed as separate class because of key
evolutionary novelties of feathers, light bones,
and super-efficient lungs
106
History of the Birds

Birds today
– adaptations for flight energy demands
 efficient respiration
 efficient circulation
 Endothermy
107
108
The “Great
Nest”
measures 9.5
ft. across, 20 ft.
deep, and
weighs an
estimated 2
tons.
109
Mammals

Key mammalian characteristics
– hair
 heat loss
 camouflage
 sensory structures
 defense weapon
– mammary glands
 about 50% of energy in milk comes from fat
110
A mother tiger, like other mammals, will
not have to leave her young in order to
find food for them
Key Mammalian Characteristics

endothermy
– crucial adaptation that allowed activity at any
time of the day to colonize severe environments

placenta
– specialized organ allowing food, water, and
oxygen to pass from mother to child

teeth
– heterodont dentition (different teeth for different
functions)
112
Neither of these animals is a fierce
carnivore, despite the appearance
of their teeth
Key Mammalian Characteristics

digestion of plants
– cellulose major source of food for herbivores
 mammals do not have necessary digestive enzymes to
break apart cellulose
– some have evolved four-chambered stomachs
– some contain mutualistic bacteria in a cecum
114
Giraffes, like cows,
possess a
chambered
stomach. All
ruminants chew
cuds
Although horses and zebras are
herbivorous like giraffes, they do not
have a rumen. Instead, they possess a
cecum.
Key Mammalian Characteristics

hooves and horns
– hooves specialized pads of keratin
– horns composed of core of bone surrounded by
keratin sheath

flight
– bats have wing of leathery membrane of skin
stretched over the bones of four fingers
 second largest order of mammals
– echolocation
117
History of the Mammals

Orders of mammals
– monotremes: egg-laying mammals
 lay shelled eggs
– marsupials: pouched mammals
 finish development in external pouch
– placental mammals
 placenta nourishes embryo throughout entire
development
 Gestation length related to size
118
echidna
The echidna is
also known as
the spiny
anteater
koala
Koala
young stay
with the
mother for
an extended
period of
time,
hitching a
ride on
mom’s back
They’re even
cute when
they’re asleep
Tasmanian devil
There
really is a
Tasmanian
devil
Tasmanian Devil
kangaroo
There are many species
of kangaroo. In addition
to the red (shown here),
there is even a species
that climbs trees
You
didn’t
believe
me, did
you?
The capybara is the world’s
largest rodent.
sloth
Star nosed
mole
Manatee?
Manatees are very docile
creatures
Notice the teeth
on this orca
Beluga whale
The blue whale can measure over 90
ft. long and weigh over 200 tons
Evolution Among Primates

Primates
– two distinct features allowed them to succeed
in arboreal environment:
 grasping fingers and toes
 binocular vision

Prosimians (lemurs and tarsiers)
– Very smell oriented
– Usually have long tails
133
The
tamarin is a
prosimian
The aye-aye is a most unusual
prosimian
Anthropoids

Higher primates - includes apes, monkeys,
and humans
– The term “Anthropoid” means “Like us”

Direct descendents:
– New World monkeys (South America)
– Old World monkeys (Africa)
136
mandrill
The
mandrill is
an
anthropoid
monkey
related to
the baboon
New world
monkeys like
this spider
monkey have
prehensile or
grasping tails.
The Old World
monkeys lack
the ability to
grasp with the
tail
The “silverback” is a mature male
gorilla who fears
nothing
gorilla
The orangutan is
found only on orang
Borneo and Sumatra
Gibbons are
gibbon extremely
athletic apes
found in
Southeast
Asia. Like
all apes,
gibbons are
tail-less
Chimpanzees have very
complex social groups,
interact often with one
another, and are very
devoted parents
Chimps have
often been
seen in the
wild using
tools. What
do you
suppose this
guy is doing
with the
stick?
Human evolution is very controversial
 Fossils are extremely rare and difficult to
interpret
 Dating of fossils is also suspect
 H. sapiens is the only surviving hominid.

– The best fossils are between 90,000 and
100,000 years old.
– Cro-Magnons replaced Neanderthals about
40,000 years ago.
– Humans of modern appearance eventually
spread across Siberia to North America about
13,000 years ago.
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