Chapter 23
The Vertebrates
Chapter 23 Outline
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23.1 Chordate
Heritage
23.2 Vertebrates
23.3 Fishes
23.4 Amphibians
23.5 Vanishing
23.6 Amniotes Intro
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23.7 Herptile
(Reptiles)
23.8 Aves (Birds)
23.9 Mammals
23.10 Primates
23.11 TBA
23.12 TBA
Impacts, Issues: Interpreting and
Misinterpreting the Past
A.The absence of transitional forms was an early
obstacle to Darwin’s theory of evolution.
1. The discovery of Archaeopteryx specimens, which
display both reptilian and bird features, was
significant.
2. Archaeopteryx lived about 150 million years ago.
B. Such fossils are witness to the history of life or
Are they???
23.1 Chordate Heritage
NOT ON EXAM, but please listen
1. Chordates are deuterostomes
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“Second Mouth”
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Examples
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Chordates
Echinoderms ***Not a chordates***
23.1a For Chordate features
1.
2.
3.
4.
Coelomates (hollow body cavity)
Bilateral
MOST are vertebrates (with a back-bone)
All chordates, at some time in their lives, have
four distinctive features:
23.1a For Chordate features
4. All chordates, at some time in their lives, have
four distinctive features:
1.
A notochord which is a long rod of stiffened tissue
that supports the body.
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2.
3.
A dorsal, tubular nerve cord
A muscular pharynx with gill slits is positioned at the
entrance to the digestive tract
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4.
Later it changes to bony units in vertebrates.
at least in the embryo
A tail, or rudiment thereof, exists near the anus
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at least in the embryo
23.1b Invertebrate Chordates
Urochordata (tunicates or Sea squirts )
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Larval stage look like a tadpole
Adult metamorphosis lose tail and notochord
Filter feeder
Cephalochordata (lancelets)
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Have all for characteristics,
Filter feeder
23.2a Trends among the Vertebrates
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“Non” craniates skull casing
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Tunicates and lancelets
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lack vertebrae
 Why can they survive w/o jaws???? HINT
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Craniates: skull casing
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All chordates (fishmammals)
23.2a Trends among the Chordates
This animation (Audio - Important) describes the evolution of chordates.
23.2a Trends among the Chordates
This animation (Audio - Important) describes the evolution of chordates.
23.2a+b Trends among the Chordates
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Craniates
Notochord replaced by Vertebral column
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Modifed near head and Jaws
Notices the loss of armored species
Jaws and Superior Sensory Organs
Tetrapods, Fins, legs
Less dependency on Gills lung
development
This animation (Audio - Important) describes the evolution of chordates.
23.2b The vertebrates are divided
into eight classes
1.
2.
Agnatha - jawless fishes
Placodermi - jawed armored fishes
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3.
4.
5.
6.
7.
8.
(extinct)
Chondrichthyes - cartilaginous fishes
Osteichthyes - bony fishes
Amphibia - Amphibians
Reptilia - Reptiles
Aves - Birds
Mammalia - Mammals
23.3a Fish Success
Streamlines bodies
 Fish scales protect the body without
weighing it down.
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3 Types of fish
Agnathans (Jawless Fish)
 Chondrichthyes (cartilaginous)
 Osteichthyes (bony fish)
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23.3a Agnathan (Jawless Fish )
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Jawless (Agnathan)
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lampreys and hagfishes
eel-like body with no paired fins.
A notochord and cartilaginous skeleton are present
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Earliest jawless fishes(Agnatha) were the
ostracoderms.
They were covered with hardened external plates
but did not have a well-developed endoskeleton.
The lived on the ocean bottom where they were filter
feeders
23.3a Agnathan (Jawless Fish )
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Jawless (Agnathan)
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lampreys and hagfishes
Ostracoderms
23.3b Jawed Fish Chondrichthyes
(cartilaginous fish)
Sharks, Skates and Rays Chimaeras
 Cartilaginous endoskeleton, fins and
unprotected gill slits
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 Lacks
an operculum Found in Bony Fish
Replaceable teeth
 Have a well developed sensory system
 NO SWIM BLADDER
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23.3c Osteichthyes (bony fishes)
1. Most numerous and diverse of the vertebrates.
a. radiated into nearly every aquatic habitat.
b. Body plans vary
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from torpedo shape to eel to the peculiar sea horse.
2. Operculum,
3. Swim Bladder
4. Extensive gills to maximize the surface area for gas exchange
5. Ectothermic
Examples, The ray-finned fishes, lobe-finned fishes, Lungfishes
Anatomy
23.3c Osteichthyes
(bony fishes)
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Most of the bony fishes have a sac like structure
leading from the pharynx.
The connection to the pharynx may be sealed off
during development.
This sac, the swim bladder, is a major development to
the bony fishes.
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It provides the fish with a neutral buoyancy.
Permits the fishes to hover in the water and not have to
swim constantly and thus expend energy to avoid sinking.
The reduction in energy expenditure reduces the
amount of time required for feeding.
23.3c Osteichthyes (bony fishes)
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Respiration in the aquatic environment is difficult for two
reasons.
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Extensive gills to maximize the surface area for gas exchange.
Use counter current system where the blood in the gill
capillaries flows in the opposite direction to the water flowing
over the gills .
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The medium contains far less oxygen per unit volume than air
its viscosity makes it more difficult to move during irrigation of the
respiratory surfaces or gills.
This allows for a higher saturation of the blood with oxygen.
Bony Operculum provides a degree of protection for the
delicate gill tissues
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By moving the operculum water can be forced over the gills without the
fish being compelled to move
23.4
Amphibians
Amphibians have a body plan and mode of reproduction
somewhere between “fishes” and “reptiles.”
Life on land presented new challenges to the emerging
amphibians.
a. Water availability was not reliable.
b. Air temperatures were variable and air itself was
not the strong supporting medium that water was, but
it was a richer source of oxygen.
c. New habitats, including vast arrays of plants,
necessitated keener sensory input.
23.4
Amphibians
BIG 5 STATEMENTS
1.
2.
3.
4.
5.
23.4
A.
Amphibians
Amphibians have a body plan and mode of reproduction somewhere
between “fishes” and “reptiles.”
1. “Amphi” meaning dual lived
a. First in water, then on land
2. All are dependent on water in juvenal stages,
a. They must return to it to lay eggs, which will produce larvae
dependent on a watery environment.
3. Most have a Moist mucus covering for respiration
a. Depending on their habitat, can respire by use of gills, lungs, skin,
and pharyngeal lining.
4. The skin is usually thin and sometimes supplied with glands that produce
toxins.
5. Ectothermic
23.4
B.
1.
2.
3.
Amphibians
Three main groups of amphibians.
23.4
B.
Amphibians
Three main groups of amphibians.
1. (Anura) Frogs and toads are the best known.
a. long powerful hindlimbs
b. excellent prey-grasping capability of the tongue attached
at the front of the mouth.
2. (Caudata) Salamanders have an elongated body with a tail
that persists into adulthood.
a. Adults may retain larval features including gills and a tail.
3. (Gymnophiona) Caecilians have lost their limbs and vision.
a. These unusual creatures live burrowed in the forest floor
where they hunt for invertebrate prey.
b. They have no limbs but do have small scales embedded
in the skin.
23.5 Vanishing Acts of Amphibians
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Several frog, toad, and salamander
species are currently listed as threatened
or endangered.
WHY???
23.5 Vanishing Acts of Amphibians
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Several frog, toad, and salamander
species are currently listed as threatened
or endangered.
Many declines correlate with:
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Shrinking and deteriorating habitats
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Pollution
Long term changes in climate
Increases in ultraviolet radiation
New diseases may be affecting amphibians
sooner than other organisms. WHY???
23.6
The Rise of Amniotes
A. The “Reptiles”
1. Four features were critical to amniotes’ escape from water
dependency.
a. Amniote eggs with covering membranes and a shell, which
allow the eggs to be laid in dry habitats.
b. Dry or scaly skin that is resistant to drying.
c. Their kidneys are good at conserving water.
2. Modification of limb bones, teeth, and jawbones
a. Development of the cortex region of the cerebrum permitted
greater integration of sensory input and motor response. WHAT?????
b. four-chambered heart and more efficient lungs allowed
greater activity.
23.7
Existing Reptilian Groups
1. (Chelonia) Turtles possess a distinctive shell
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protection while
conserving water and body heat.
Turtle eggs are vulnerable to predators, resulting in
declining numbers.
2. (Sauria) Lizards are the most diverse reptiles.
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Most lizards are small-bodied insect eaters; their most
usual habitats are deserts and tropical forests.
Some such as the monitor lizard can subdue deer.
a long snout; body temperature is regulated behaviorally
(ectothermic).
They show complex behavior, as when the parents guard
nests and assist hatchlings into the water.
23.7
Existing Reptilian Groups
3. (Serpentes ) Snakes
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descended from short-legged, long-bodied lizards.
All are carnivores, many with flexible jaws that permit
swallowing quite large, whole prey.
Snakes are limbless but retain vestiges of hind limbs.
Many are venomous and may bite humans, especially when
provoked.
4. (Crocodilia) Crocodiles and alligators
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all live in or near water
5. (Rhynchocephalia) the tuatara
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has a single living member
a lizardlike reptile of New Zealand.
You might have thought tuatara
are lizards… but they’re not.
(Rhynchocephalia) the tuatara
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The arrangement of their teeth is very special. The single row of
teeth in the lower jaw fits between two rows of teeth in the upper
jaw. This helps tuatara tear apart hard insects such as weta, and
chew the heads off small seabirds – yuck!
Tuatara mate differently fromlizards. The male tuatara does not
have a penis; he mounts the female and passes sperm straight
from his cloaca to hers (the cloaca is the hole that sperm enters
the female through).
They have a gland beneath the skin on the head, which contains
a simple ‘third eye’.
Lizards have visible ear openings but tuatara do not.
But like lizards, if they lose their tails they are able to regrow them
- excellent!
What’s this about a ‘third eye’ ??
23.8 Birds—The Feathered Ones
A. Theorized ancestral relationship to reptiles
B. Birds have several unique features.
 Feathers covering the wings make a good flight surface and
conserve metabolic heat in the body.
a. ENDOTHERMIC
 Heat is generated and regulated from within the body
 Heart is four-chambered, and the lungs are highly efficient
 Bones are lightweight due to air cavities within them.
 Powerful muscles are attached at strategic places on the bones
for maximum leverage.
a. Keeled sternum
C. Migration is a dramatic form of behavior.
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Seasonal day length is a triggering factor.
Most of the travel, sometimes very long distances, is from breeding
grounds and wintering places.
23.9
Mammals
A. Modern mammals are characterized by:
 Hair covers at least part of the body (whales are an
exception).
 Milk-secreting glands nourish the young.
 Dentition (incisors, canines, premolars, and molars)
specialized to meet dietary habits.
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Brain capacity is increased, allowing more capacity for
memory, learning, and conscious thought.
Show behavioral flexibility, the ability to expand on the
basics with novel forms of behavior.
23.9c What are the Three Types of
Mammals:
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1.
2.
3.
23.9c Three Types of Mammals:
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Monotremes (Egg-laying) mammals
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Marsupials (Pouched) mammals
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Ex. platypus and Echidna (spiny anteater) in Australia.
They are practically toothless.
They lay eggs but suckle their young.
Ex. opossum of North America, Kangaroo, Sugar Glider
give birth to tiny, blind, hairless young that find their way
to the mother’s pouch where they are suckled and finish
their development.
Placental mammals (all the rest)
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You mice, dogs, cows, horse
nourish their young within the mother’s uterus by the
placenta—a composite of maternal and fetal tissue.
Stop
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it’s Hammer time
links
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http://io.uwinnipeg.ca/~simmons/16cm05/1
116/chordate.htm
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http://trc.ucdavis.edu/biosci10v/bis10v/we
ek5/06week5day1.html
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