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VERTEBRATE ZOOLOGY
(VZ Lecture10 – Fall 2012 Althoff - reference PJH Chapters 8 &9)
Tetrapods: Origins & Radiation
PART II
Moving on Land
• Locomotion on land is energetically more costly
•
•
•
than in water. Walking on land takes more energy
than flying which takes more than swimming
Most tetrapods accomplish locomotion by moving
diagonal pairs of legs together (see Fig. 8-7, p174).
Even humans retain “some” of this (e.g., right arm
forward when left leg strides forward)
Primitive mode exhibited by modern day
salamanders: forces comes from ______ muscles,
_____________ muscles
Much advanced: swimming, walking, & jumping
modes by frogs  highly specialized ____ muscles
Advancements: Primitive tetrapods 
Amniotes
• Amniotes first to have “the _____”…where each limb
•
•
•
moves independently in succession, usually with 3
feet on the ground at a time
The ______ is a sped-up walk….only 1 or 2 feet on
the ground at a time.
______ is faster movement yet, involves diagonal
pairs of limbs moving together.
Then, a new faster mode is the ________—found in
some mammals. Jumping off hind legs and landing
on forelegs with flexion of the back contributing to
the length of the stride.
Eating on Land
• Early tetrapods:
•
•
wide, flat skulls and elongated
snout resulting in most of tooth row in front of eyes
________: Fishes  small and bony
Tetrapods  large and muscular…
increasing manipulation of food
--some (frogs, lizards salamanders)
can project tongue to capture prey
______________: only in terrestrial vertebrates
advantagemoisten “dry” food, start
digestion. Other specializations for
some species (i.e., venom: lizards/snakes
Changes in Branchiomeric Musculature
(from ancestral pharyngeal arches)
• With loss of gills, much of musculature of associated
•
•
with gill movement has been lost in tetrapods
Exception: gill levers. In fishes, the muscle mass is
a single unit (the cucullaris). In tetrapods, it
becomes the tapezius (runs from top of the neck and
shoulders to the shoulder girdle)
Major branchiomeric muscles of tetrapods are
associated with feeding and feeding only. This
mean those associated with the mandibiles (ex.
crushing food in some tetrapods) and hyoid arches
(help open mouth and aids in swallowing food)
(see Fig. 8-10, p179 for generalized tetrapod condition)
Breathing Air: changes from nonamniotic
to amniotic tetrapods
• Nonamniotic tetrapods:
•
•
uses __________-pressure
buccal pump to inflate lungs. Lungs are “simple”
Amniotic tetrapods: use ____________-pressure
aspiration pump.
Inhalation: rib cage expands by hypaxial
muscles sucking air in
Exhalation: compression of, mainly achieved
by elastic return of rib cage, reduction
of lung capacity
Amniotes: lungs subdivided, usually complex
resulting in significant increase in _____________
for gas exchange
Breathing:
INSPIRATION
• Rib cage moves
up & out
• Diaphragm
contracts and
moves down
• Pressure in
lungs
decreases—air
rushes in.
Breathing:
EXPIRATION
• Rib cage moves
down and in
• Diaphragm relaxes
and moves up
• Pressure in lungs
increases and air
is pushed out
Pumping Blood Uphill & Double Circulation
• In H20, blood is weightless…only significant
•
•
challenge to the heart is fluid resistance
Circulation more difficult for terrestrial animals:
a) blood tends to pool in low spots
b) must be forced through the veins, back up to
the heart
--this requires ________ blood pressure
Another tetrapod advancement: double-circuit
cardiovascular system:
a) __________ circuit  rich O2 blood to body
b) ____________ circult  low O2 blood to lungs
Atrium always completed divided
Ventricle sometimes “fixed” barrier division
Fig. 8-11 p180 PJH
Sensory System Advancements
• Switch is from “liquid” transmission medium to “air”
• Lateral line system of fishes won’t work in air
•
•
•
•
medium because air is not dense enough to
stimulate the mechanical receptors there
If molecules light enough to be suspended in air,
then chemical systems work fine for sense of smell
Vision and hearing in air can offer advantages over
those in a liquid medium
Vision: easier on land because light is transferred
through air with less disturbance than through H2O
Vision: most tetrapods re-shape lens to focus
(snakes move lens to focus eye…like fishes)
Hearing
• “middle ear” in
tetrapods serves to
amplify sound
• Fluids of inner ear
compressed, with the
waves stimulating hair
cells in organ of Corti
(within lagena…
cochlea in mammals)
• ___________ much
enlarged in tetrapods

Fig. 8-15 p186 PJH
FROG
lagena
LIZARD
lagena
Olfaction
• Some sensitivities up
to 1 million trillion
(1015) part of air
• Mammals…with very
highly developed
olfaction…aided by
presence of
_____________: thin
bone lined with
olfactory epithelium
• vomeronasal organ
(Jacobson’s organ)
Fig. 8-16 p186 PJH
GENERALIZED MAMMAL CONDITION
maxilloturbinates
UNGULATE CONDITION
vomeronasal organ
Dry Environments: Must conserve H20
• Losses through body surfaces (skin) and
•
•
•
respiratory system…and through the kidney
Partially overcome rapid skin water loss with
increased thickness (in amniotes compared to
fishes and amphibians) of ___________________
(keratinized epidermal cells)
These keratinized cells are:
a) insoluble in water (providing some “waterproofing”
b) resist physical wear
However, lipids in skin most responsible for limiting
evaporative water loss
Fig. 8-18 p189 PJH
The Energy “Game”: 4 major “external”
influences
 ________________________
 ________________________
 ________________________
 ________________________
the impact
of all of
these can be
addressed by
the animals
behavior….!!