Evolution of the Tetrapods
Evolution of the Tetrapods
Vertebrates
The Origin of Tetrapods
The first vertebrates on land were
amphibians in the Devonian (400 mya)
 Arose from the rhipidistian (a family of
lobed finned fish) (based on morhpology)
or a lungfish (DNA)

Origin of
Tetrapods
Origin of Tetrapods
Classification
 Phylum:
Chordata
 Subphylum: Vertebrata
 Superclass: Gnathostomata
 Class: Amphibia
– Order: Urodela (Salamanders)
– Order: Anurans (Frogs and Toads)
– Order: Apodans (Caecilians)
Class: Amphibia
Two lives
– refers to metamorphosis of many frogs
 Skin smooth and moist (cutaneous
respiration)
3
 _____
chambered heart with a double
circulation system
 Mesolecithal eggs with jelly-like
membrane

Order: Urodela
400 species
 Salamanders
 Retain their tail as
adults
 Limbs are at right
angles to the body
 Carnivorous
 Most have internal
fertilization using a
Spermatophore
_____________
 Axolotl paedomorphosis

Order: Anurans
3500 species
 Frogs and Toads
 Lose their tail as
adults
 Hind limbs are
adapted for jumping
 Tongue connected
to front of mouth
 Secrete mucus
External
 __________
Fertilization

Order: Apodans
150 species
 Caecilians
 Legless and blind
 Mostly Tropical
Internal
 __________
Fertilization
 Usually give birth
to live young.

Gas
Exchange
Conditions for Respiratory
Surfaces
 Large
 Thin
 Moist
surface area
Aquatic vs. Terrestrial
1
Less than ____%
oxygen
 Oxygen amounts
decrease as the
temperature
increases
 Aquatic animals
use large amounts
of energy to obtain
20
oxygen (____%)

21
About _____%
oxygen
 Developed
invaginations to
increase surface
area and decrease
evaporation
 Terrestrial animals
may use only 1% 2% of its energy to
obtain oxygen

Respiratory Surfaces
 Cutaneous
Respiration
 Gills
 Tracheal
 Lungs
Systems
Cutaneous Respiration
 Direct
diffusion of gases between the
organism and the environment
 Found in Porifera, Cnidarians,
Platyhelminthes, nematodes,
Annelids, and some Amphibians
 Supplements other organisms
(amphibians)
Gills
Found in echinoderms, mollusks,
annelids,
arthropods, some
vertebrates
 Countercurrent
Gas Exchange

Countercurrent Gas Exchange
Maintains gradient over the whole length of
the capillaries
80
 Extracts ____%
of the oxygen from the
water

Tracheal Systems
Found in arthropods
 Tracheae

– open tubes

Spiracles
– openings

Tracheoles
– contact with cells

Muscle
– increase amount of
Carbon Dioxide
removed
Tracheal Systems
Diffusion Lungs
 Found
in invertebrates
 Gas moved primarily by diffusion
– may be increased by body movement
 Modifications
– snails - cavity with gill modified into
lung
– scorpions and spiders - invaginations of
the abdomen
Ventilation
Lungs
Found in
amphibians,
reptiles,
mammals
and birds
 Pharynx
 Larynx
 Trachea
 Bronchi
 Bronchioles
 Alveoli

Alveoli
Ventilating The Lungs

_______
Positive Pressure
Breathing
– pushes air down
trachea
– seen in frogs and
other
amphibians

Negative Pressure
________
Breathing
– suction created
by diaphragm
– seen in
mammals
Negative Pressure Breathing
Amniotic Egg
Evolution of the _________
 Allows
animals to complete their
entire life cycle on land
 Has shell that retains water (or is
lost when kept inside mammals)
 Specialized extraembryonic
membranes (not part of the animal)
The Amniotic Egg
Evolution of the Amniotic Egg
 Amnion
- Protects from dehydration
and mechanical shock
 Yolk Sac - Nutrient storage
 Albumin (egg white) - Nutrient
storage
 Allantois - stores waste, gas
exchange
 Chorion - gas exchange
Amniotes
Amniotes
How Reptiles differ from
Amphibians
Tough, dry skin
 Amniotic egg
 Crushing or
gripping jaws
 Copulatory organs
 More efficient
circulatory system
with a higher blood
pressure

More developed
lungs (thoracic
breathing)
 Better water
conservation
 Better body
support and limbs
 Better nervous
system

Classification
 Phylum:
Chordata
 Subphylum: Vertebrata
 Superclass: Gnathostomata
 Class: Reptilia (not real)
– Class: Testudines (Turtles and
Tortoises)
– Class: Spenodontia (Tuataras)
– Class: Squamata (Lizards and Snakes)
– Class: Crocodilia (Crocodiles and
Alligators)
Reptile
Radiation
Synapsids
(therapsids) led to
mammals
 Sauropsids

Anapsid
– _________
(turtles)
Diapsid
– _________
(all others)
Class: Testudines (Chelonia)

Protective Shell
– Carapace (top)
– Plastron (bottom)

Land and Sea Evolved on land
and returned to
water (lay eggs
on land)
Largest,
Leatherback
Sea Turtle
(2,000 lbs!)
Class: Testudines (Chelonia)
teeth
No _____
 Most move legs
to breathe
 TDS (low:male
high:female)

Class: Sphenodontia

Tuataras
___________
– Two living species
(New Zealand)
– Not a True Lizard
(no external ears,
different teeth)
– Very Primitive
(similar to
mesozoic reptiles
– Well developed
eye below skin?
Class: Squamata

Lizards
– geckos, iguanas,
skinks, chameleons
terrestrial, burrowing,
aquatic, arboreal
 moveable eyelids (in
most)
 Paired copulatory
organs

Class: Squamata
Tongue usually not
bifurcated
 Lower jaw loosely
connected to skull
 TSD (female to male)
Parthenogenesis
 ______________

Class: Squamata
Class: Squamata
Class: Squamata
Class: Squamata
Gila Monster –
• One of two
poisonous lizards
• Protein in saliva
studied to treat
diabetes.
Class: Squamata
Snakes
 Lack limbs
 Lack moveable
eyelids

Class: Squamata
Bifurcated tongue
Jacobson’s organ
 _________
 Pit Vipers (Loreal
Pits)

Class: Squamata

Venom
– Viperidae (Folding
Fangs)

Rattlesnakes
– Elapidae (Fixed
Front Fangs)
 Cobras,
Sea Snakes,
Coral Snakes
– neurotoxic
– hemotoxic
Class: Squamata
Class: Squamata
Class: Squamata
Feeding
Adaptations
 Teeth
curved and pointed inward
Quadrate
 Hinged __________
bone
 Bones of jaw are attached by
muscles and ligaments
 Moveable palate
 Elastic skin
 No sternum
Largest living
reptiles
 Most closely
related to
dinosaurs
 Complete
secondary
palate
________
 Four
chambered
heart (?)
 Nest
temperature
(female/male)

Class: Crocodilia
Dinosaurs and Pterosaurs

Dinosaurs
–
–
–
–
Ornithischian
Saurischian
Pterosaurs
flying reptiles
Animal Structure
and Function
(4th exam)
Animal Nutrition
Nutritional
Requirements

Undernourished
– not enough
calories

Overnourished
– too many calories

Malnourished
____________
– missing one or
more essential
nutrients
Essential Nutrients
 Essential
Amino Acids
 Essential Fatty Acids
 Essential Vitamins
 Essential Minerals
Essential Amino Acids

Found in proteins
– 20 different types

8 essential in adult
humans (9 infants)
 all
in animal proteins
 vegetarians need to
eat grains and beans
Histidine
__________ – Essential in infants
Essential Fatty Acids
 Unsaturated
fatty acids
– used to make phospholipids for
membranes
Essential Vitamins
 Fat
Soluble
– stored in fat
D, A, K, E
– ___________
 Water
Soluble
– excreted in urine
– B complex and C
Essential Minerals
 Inorganic
nutrients
– Calcium & Phosphorous
 bones
– Iron
 anemia
– Iodine
 thyroid
hormones
– Sodium, Chlorine, & Potassium
 nerve
function, water regulation
Food Types

Heterotrophic
–
–
–
–
Herbivores
Carnivores
Omnivores
Insectivores
Feeding Adaptations

Suspension
Feeders
Feeding Adaptations
 Substrate
Feeders
Feeding Adaptations
 Fluid
Feeders
Feeding Adaptations
 Bulk
Feeders
Intracellular Digestion
Inside cells
 All animals
 Exclusive in:

– Protista
– Porifera
Extracellular Digestion
 Outside
cells
 All animals above the sponges
 Two Types
Gastrovascular Cavity
– _________________
Alimentary Canal
– _________________
Gastrovascular
Cavity
One opening
 Found in
Cnidaria and
Platyhelminthes

Alimentary Canal
Two openings
 Allows for
specialization

–
–
–
–
–
–
–
–
Mouth
Pharynx
Esophagus
Crop
Gizzard
Stomach
Intestine
Anus
Mammalian Digestion
 Accessory
Glands
– salivary glands
– pancreas
– liver (emulsification)
– gallbladder
 Peristalsis
 Sphincters
 “Food”
– bolus
– acid chyme
– feces
Macromolecule Digestion
Mouth
Carbo Protein Nucleic Fat
Acids
Initial
Stomach
Initial
Intestine Main
Main
Initial
Main
Initial
Main
Dentition and
Diet
Nonmammal
vertebrates
 Carnivores

– canines
(grasping/puncturing
)
– incisors (tearing)
– molars and
premolars
 (crushing
grinding)
Herbivores
 Omnivores

and
Digestive Tracts

Carnivores

Herbivores
shorter
– ________
digestive
system
– small
cecum
Longer
– ________
digestive
system
– large cecum