IB-202-7
5-29-06
The Amniotes
• Amniotes also have other terrestrial
adaptations
– Such as relatively impermeable skin and the
ability to use the rib cage to ventilate the
lungs
– Amphibians pump up their lungs by “gulping”
air. Also much gas exchange through the
moist skin
Early Amniotes
• Early amniotes
– Appeared in the Carboniferous period
– Included large herbivores and predators
• A phylogeny of amniotes
Diapsid referrs to
two holes in the
skull.
Synapsid referrs to
a single hole in the
skull (would be the
lower jaw fits into
the zygomatic arch
and the jaw muscle
attaches to the
temporal region of
the skull
Saurischians
Dinosaurs
Lepidosaurs
Archosaurs
Synapsids
Diapsids
Reptiles
Ancestral
amniote
Figure 34.23
Reptiles
• The reptile clade includes
– The tuatara, lizards, snakes, turtles,
crocodilians, birds, and the extinct dinosaurs
• Reptiles (including birds)
– Have scales that create a waterproof barrier
– Lay shelled eggs on land
Figure 34.25
Metabolic rate and body
temperature
• Most reptiles are ectothermic (cold blooded)
– Absorbing external heat as the main source of
body heat because they generate little heat
with their low metabolism
• Birds and mammals are endothermic
– Capable of keeping the body warm through
metabolism by conserving heat—if too warm
they have mechanisms for losing heat
The Origin and Evolutionary
Radiation of Reptiles
• The oldest reptilian fossils
– Date to about 300 million years ago
• The first major group of reptiles to emerge
– Were the parareptiles, which were mostly
large, stocky herbivores (extinct)
• A phylogengy of amniotes
The diapsids are
composed of two main
lineages
Saurischians
As parareptiles were
dwindling the diapsids
were diversifying and give
rise to two linages the
lepidosaurs and the
archosaurs
Dinosaurs
Lepidosaurs
Archosaurs
Synapsids
Diapsids
Reptiles
Ancestral
amniote
Figure 34.23
• The dinosaurs
– Diversified into a vast range of shapes and
sizes
– Included the long-necked giants called the
theropods
• Traditionally, dinosaurs were considered
slow, sluggish creatures
– But fossil discoveries and research have led to
the conclusion that dinosaurs were agile and
fast moving
• Paleontologists have also discovered signs
of parental care among dinosaurs
Figure 34.26
Lepidosaurs
• One surviving lineage of lepidosaurs
– Is represented by a species of lizard-like reptile called
tuatara (differs from other lizards in that it has the
unmodified diapsid skull-two disticnt holes)
Figure 34.27a
(a) Tuatara (Sphenodon punctatus)
• The other major living lineage of lepidosaurs
– Are the squamates, the lizards and snakes
• Lizards
– Are the most numerous and diverse reptiles, apart
from birds. Three chamber heart (amphibians 2
chambered heart)
Figure 34.27b (b) Australian thorny devil
lizard (Moloch horridus)
• Snakes are legless lepidosaurs
– That evolved from lizards and some even
retain vestigial pelvic and limb bones
indicating that their ancestors had legs
(c) Wagler’s pit viper (Tropidolaemus wagleri), a snake
Figure 34.27c
• All turtles have a boxlike shell
– Made of upper and lower shields that are fused to the
vertebrae, clavicles, and ribs
– Turtles have adapted to deserts, ponds, rivers and the
oceans
Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina)
Alligators and Crocodiles
• Crocodilians
– Belong to an archosaur lineage that dates back to the late
Triassic. Live in warm environments. Lay egg in nests that they
guard. Parental care.
Figure 34.27e (e) American alligator (Alligator mississipiensis)
Birds
• Birds are archosaurs (7000 species)
– But almost every feature of their reptilian
anatomy has undergone modification in their
adaptation to flight
• Many of the characters of birds
– Are adaptations that facilitate flight
• A bird’s most obvious adaptations for flight
– Are its wings and feathers
No teeth
Only 1
ovary/testis
No urinary
bladder
Finger 1
(b) Bone structure
Palm
Light weight
skull
(a) wing
Finger 2
Forearm
One way air
flow in lungs
Wrist
Shaft
Vane
Shaft
Figure 34.28a–c
Finger 3
Barb
Barbule
Hook
(c) Feather structure
The Origin of Birds
• Birds probably descended from theropods
– A group of small, carnivorous dinosaurs that
had feathers, but not capable of fight
Transitional form (Dino to bird)
• By 150 million years ago
– Feathered theropods had evolved into birds
• Archaeopteryx
– Remains the oldest bird known
Wing claw
Toothed beak
Teeth
Wing claw
Long tail with vertebrae
Later forms show progressive
loss of these characters.
Airfoil wing with
contour feathers
Figure 34.29
Long tail with
many vertebrae
Living Birds
• The ratites, order Struthioniformes
– Are all flightless. Lack “big” pectoral muscle and sternum keel.
(a) Emu. This ratite lives in Australia.
Figure 34.30a
• The demands of flight
– Have rendered the general body form of
many flying birds similar to one another
(b) Mallards. Like many bird species,
the mallard exhibits pronounced color
differences between the sexes.
(c) Laysan albatrosses. Like most birds,
Laysan albatrosses have specific
mating behaviors, such as this
courtship ritual.
(d) Barn swallows. The barn swallow is a member of
the order Passeriformes. Species in this order are
called perching birds because the toes of their feet
can lock around a branch or wire, enabling the bird
Figure 34.30b–d
to rest in place for long periods.
Structure Function
• Foot structure in bird feet
– Shows considerable variation
Perching bird
(such as a
cardinal)
Figure 34.31
Grasping bird
(such as a
woodpecker)
Raptor
(such as a
bald eagle)
Swimming bird
(such as a duck)
Feeding Adaptations
• Both the feet and beaks of birds show
structures best suited for their life style.
• With regards to beaks some adapted for
tearing like a hawk’s beak, flamingos filter
plankton out of the water, woodpecker for
pecking holes in rotten trees and
extracting insects, seed eaters and New
Zealand kee wee with a long beak for
probing into soft ground for worms.
Mammals
• Mammals are amniotes that have hair and
produce milk
• Mammals, class Mammalia
– Are represented by more than 5,000 species.
Most are placental mammals.
Derived Characters of Mammals
• Mammary glands, which produce milk
– Are a distinctively mammalian character
• Hair is another mammalian characteristic
• Mammals generally have a larger brain than other
vertebrates of equivalent size
• Endotherms with a closed 4 chambered heart
• Ventilate lungs with a diaphragm
• In contrast to the conical teeth of reptiles mammals have
specialized teeth. Grinding molars for grass eaters,
carnivores have stabbing canines, shearing premolars and
molars for crushing bone. Teeth specialized for diet.
• Example of specialized dentition in fish and seals.
Early Evolution of Mammals
• Mammals evolved from synapsids in the late
Triassic period but were small and remained
insignificant because most of the ecological niches
were filled by the dinosaurs of various sizes and
forms.
Mammals at that time were probably nocturnal (night
forms), hid in burrows and fed on insects.
After the dinosaurs died off at cretaceous tertiary boundary
(maybe mostly due to the impact of a large asteroid) then
there was an adaptive radiation of the mammals and they
then filled the niches formerly occupied by the dinosaurs.
Evolution of the mammal ear
• The jaw was remodeled during the evolution of
mammals from nonmammalian synapsids
– And two of the bones that formerly made of the jaw
joint were incorporated into the mammalian middle
ear
Jaw joint
Key
Jaw joint
Dentary
Angular
Squamosal
Articular
Quadrate
Dimetrodon
Morganucodon
(a) The lower jaw of Dimetrodon is composed of several fused bones; two small bones, the quadrate
and articular, form part of the jaw joint. In Morganucodon, the lower jaw is reduced to a single bone,
the dentary, and the location of the jaw joint has shifted.
Middle ear
Stapes
Eardrum
Inner ear
Middle ear
Inner ear
Eardrum
Stapes
Sound
Sound
Incus (evolved
from quadrate)
Malleus (evolved
from articular)
Figure 34.32a, b
Morganucodon
Dimetrodon
(b) During the evolutionary remodeling of the mammalian skull, the quadrate and articular bones became incorporated
into the middle ear as two of the three bones that transmit sound from the eardrum to the inner ear. The steps in
this evolutionary remodeling are evident in a succession of fossils.
Three linages of mammals evolved
• Monotremes- egg layers (3 species)
• Marsupials– pouched mammals having a
limited embryological development during
the short gestation period in uterus. They
finish development in a pouch obtaining
nutrient from a milk nipple.
• Placental mammals- development takes
place only in the urterus
• Monotremes
Monotremes
– Are a small group of egg-laying mammals consisting
of echidnas and the platypus
Found only in
Australia and
New Guinea
Have hair,
produce milk
but no nipples.
Duck billed
platypus (odd
looking
creature)
Figure 34.33
Marsupials
• Marsupials
– Include opossums, kangaroos, and koalas
Australian Marsupials
• A marsupial is born very early in its
development
– And completes its embryonic development
while nursing within a maternal pouch called a
marsupium
(a) A young brushtail possum. The young of
marsupials are born very early in their
development. They finish their growth
while nursing from a nipple (in their
mother’s pouch in most species).
Hind limbs are just buds.
Mother fertilized after giving
birth (33 days) and carries a
fertilized egg in the uterus
that does not develop unless
she looses the juvenile in her
pouch.
Figure 34.34a
• In some species of marsupials, such as the
bandicoot
– The marsupium opens to the rear of the mother’s
body as opposed to the front, as in other marsupials
(b) Long-nosed bandicoot. Most bandicoots
are diggers and burrowers that eat mainly
insects but also some small vertebrates and
plant material. Their rear-opening pouch helps
protect the young from dirt as the mother digs.
Other marsupials, such as kangaroos, have a
pouch that opens to the front.
Figure 34.34b
• In Australia, convergent evolution
– Has resulted in a diversity of marsupials that
resemble eutherians in other parts of the world
Marsupial mammals
Plantigale
Many marsupials
threatened to day. Cane
toad introduced to eat
insects in sugar cane
fields now eaten by some
cat sized marsupials.
Problem is there are
poisonous secretions on
the back of the cane toad
and it kills the marsupial.
Marsupial mole
Tasmanian tiger.
Figure 34.35
Deer mouse
Mole
Sugar glider
Flying squirrel
Wombat
Woodchuck
Tasmanian devil
Kangaroo
Law against toad licking.
Eutherian mammals
Wolverine
Patagonian cavy
Although marsupials
originated in the americas,
only a few remain. The
reason is they have been outcompeted by the placental
mammals. Why are
marsupials so abundant
in Australia? Because no
placental mammals and the
reason for that is the land
masses separated before
the placentals could reach
Australia. Thus no natural
placental mammals in
Australia.
Eutherians (Placental
Mammals)
• Compared to marsupials
– Eutherians have a longer period of pregnancy
• Young eutherians
– Complete their embryonic development within
a uterus, joined to the mother by the placenta
• Phylogenetic relationships of mammals
This clade of eutherians evolved
in Africa when the continent
was isolated from other
landmasses. It includes
Earth’s largest living land
animal (the African elephant),
as well as species that weigh
less than 10 g.
All members of this clade,
which underwent an adaptive
radiation in South America,
belong to the order Xenarthra.
One species, the nine-banded
armadillo, is found in the
southern United States.
Monotremata
Marsupialia
Monotremes
Marsupials
Ancestral mammal
Figure 34.36
This is the largest eutherian
clade. It includes the rodents,
which make up the largest
mammalian order by far, with
about 1,770 species. Humans
belong to the order Primates.
Proboscidea Sirenia
Tubulidentata
Hyracoidea
Afrosoricida (golden
moles and tenrecs)
Macroscelidea
(elephant shrews)
Xenarthra
Rodentia
Lagomorpha
Primates
Dermoptera
(flying lemurs)
Scandentia
(tree shrews)
This diverse clade includes terrestrial
and marine mammals as well as bats,
the only flying mammals. A growing
body of evidence, including Eocene
fossils of whales with feet,
supports putting whales in
the same order (Cetartiodactyla)
as pigs, cows, and hippos.
Carnivora
Cetartiodactyla
Perissodactyla
Chiroptera
Eulipotyphla
Pholidota
(pangolins)
Eutherians
Possible phylogenetic tree of mammals.
All 20 extant orders of mammals are listed
at the top of the tree. Boldfaced orders
are explored on the facing page.
• The major eutherian orders
MAIN
CHARACTERISTICS
ORDERS
AND EXAMPLES
Lay eggs; no
nipples; young
suck milk from
fur of mother
Monotremata
Platypuses,
echidnas
ORDERS
AND EXAMPLES
Proboscidea
Elephants
Koala
Long, muscular
trunk; thick,
loose skin; upper
incisors elongated
as tusks
Tubulidentata
Aardvark
African elephant
Teeth consisting of
many thin tubes
cemented together;
eats ants and termites
Aardvark
Aquatic; finlike
forelimbs and
no hind limbs;
herbivorous
Sirenia
Manatees,
dugongs
Embryo completes
development in
pouch on mother
Marsupialia
Kangaroos,
opossums,
koalas
Echidna
MAIN
CHARACTERISTICS
Hyracoidea
Hyraxes
Rock hyrax
Short legs; stumpy tail;
herbivorous; complex,
multichambered
stomach
Manatee
Xenarthra
Sloths,
anteaters,
armadillos
Reduced teeth or
no teeth; herbivorous
(sloths) or carnivorous
(anteaters,
armadillos)
Rodentia
Squirrels,
beavers, rats,
porcupines,
mice
Chisel-like, continuously
growing incisors worn
down by gnawing;
herbivorous
Red squirrel
Tamandua
Lagomorpha
Rabbits,
hares, picas
Chisel-like incisors;
hind legs longer than
forelegs and adapted
for running and
jumping
Primates
Lemurs,
monkeys,
apes,
humans
Golden lion
tamarin
Jackrabbit
Carnivora
Dogs, wolves,
bears, cats,
weasels, otters,
seals, walruses
Sharp, pointed canine
teeth and molars for
shearing; carnivorous
Perissodactyla
Horses,
zebras, tapirs,
rhinoceroses
Hooves with an
even number
of toes on each
foot; herbivorous
Chiroptera
Bats
Frog-eating bat
Bighorn sheep
Cetaceans
Whales,
dolphins,
porpoises
Figure 34.36
Pacific whitesided porpoise
Hooves with an
odd number of toes
on each foot;
herbivorous
Indian rhinoceros
Coyote
Cetartiodactyla
Artiodactyls
Sheep, pigs
cattle, deer,
giraffes
Opposable thumbs;
forward-facing eyes;
well-developed
cerebral cortex;
omnivorous
Aquatic; streamlined
body; paddle-like
forelimbs and no
hind limbs; thick
layer of insulating
blubber; carnivorous
Eulipotyphla
“Core insectivores”: some
moles, some
shrews
Adapted for flight; broad
skinfold that extends
from elongated fingers
to body and legs;
carnivorous or
herbivorous
Diet consists mainly
of insects and other
small invertebrates
Star-nosed
mole
Primates
• The mammalian order Primates include
– Lemurs, tarsiers, monkeys, and apes
• Humans are members of the ape group
Derived Characters of Primates
• Most primates
– Have hands and feet adapted for grasping
• Primates also have
– A large brain and short jaws
– Forward looking eyes close together on the
face, providing depth perception (binocular
vision)
– Well developed parental care and complex
social behavior
– A fully opposable thumb
The other two groups are
– The tarsiers of Southeast Asia
– The anthropoids, which include monkeys and
hominids worldwide
•
There are three main groups of living primates
– The lemurs of Madagascar and the lorises and pottos of tropical Africa and
southern Asia (many endangered because of deforestation)
– The tarsiers of Southeast Asia
– The anthropoids, which include monkeys and hominids worldwide
The oldest known anthropoid fossils, about 45 million years old
– Indicate that tarsiers are more closely related to anthropoids than
lemurs
20
30
40
50
Figure 34.38
60
Ancestral primate
Humans
Chimpanzees
Gorillas
Orangutans
Gibbons
Old World monkeys
New World monkeys
10
Lemurs, lorises, and pottos
0
Tarsiers
Anthropoids
Millions of years ago
•
Living Primates
– A lemur from Madagascar (many endangered because of
deforestation)
Figure 34.37
Evolution of Monkeys
• The first monkeys
– Evolved in the Old World (Africa and Asia)
• The fossil record indicates that monkeys first
appeared in the New World (South America)
during the Oligocene (30 mya) after the
separation of Africa from S. America. Thought
that they may have been rafted over from Africa
on logs. Monkeys on both continents underwent
separate adaptive radiations and are quite
different.
• New World and Old World monkeys
– Underwent separate adaptive radiations during their
many millions of years of separation
Aboreal,
social diurnal.
Figure 34.39a,
Both aboreal
and grounddwelling. Social.
(a) New World monkeys, such as spider
(b) Old World monkeys lack a prehensile tail, and their nostrils
monkeys (shown here), squirrel monkeys, and
open downward. This group includes macaques (shown here),
capuchins, have a prehensile tail and nostrils
mandrills, baboons, and rhesus monkeys.
that
open
to
the
sides.
b
• The other group of anthropoids, the
hominoids diverged from monkeys 25 mya
– Consists of primates informally called apes
(a) Gibbons, such as this Muller's gibbon, are
found only in southeastern Asia. Their very
long arms and fingers are adaptations for
brachiation.
(b) Orangutans are shy, solitary apes that live in the rain
forests of Sumatra and Borneo. They spend most of
their time in trees; note the foot adapted for grasping
and the opposable thumb.
Figure 34.40a–e
(d) Chimpanzees live in tropical Africa. They
feed and sleep in trees but also spend a
great deal of time on the ground. Chimpanzees
are intelligent, communicative, and social.
(e) Bonobos are closely
related to chimpanzees
but are smaller. They
survive today only in the
African nation of Congo.
(c) Gorillas are the largest apes: some
males are almost 2 m tall and weigh
about 200 kg. Found only in Africa, these
herbivores usually live in groups of up to
about 20 individuals.
The Earliest Humans
• Hominoids diverged from Old World
monkeys about 20–25 million years ago
• Humans are bipedal hominoids with a
large brain
• Homo sapiens is about 160,000 years old
– Which is very young considering that life has
existed on Earth for at least 3.5 billion years
Important mile stones in vertebrate
evolution
• Appearance of a vertebral column for support
(early fish)
• Head, skull and associated sensory organs
• Jaws for feeding specialization
• Appendages (fins and limbs)
• Transition from water to land, but reproduction
still tied to the aquatic environment
• Amniotic egg allowed for reproduction in dry
environments.
• Adaptative radiations in fish and mammals with
tooth specialization
Friday (Chapt 40,all)
Basic principles of animal form and
function
• Next week chpt 41 all, animal nutrition