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Phylum Chordata
3 Subphyla:
• Urochordata – tunicates (sea squirts)
• Cephalochordata - lancets
• Vertebrata - vertebrates
Urochordata
Tunicates (Sea squirts) are
INVERTEBRATES
Cephalochordata
• Lancets are INVERTEBRATES
Vertebrata
• Vertebrates are …VERTEBRATES!
New Characteristics
All members of Phylum Chordata have a
• Notochord
• Hollow Dorsal Nerve Cord
• Pharyngeal Pouches
• Postanal tail
Notochord
A rod-like structure between the digestive
system and the Dorsal Hollow Nerve Cord.
In vertebrates, this develops into
the BACKBONE
It anchors muscles and allows rapid
movements
Dorsal Hollow Nerve Cord
A tube of cells
surrounding a fluid-filled
canal above the
Notochord.
This develops into
the SPINAL CORD.
The anterior portion develops into the brain and
pairs of nerves connect to blocks of muscle.
Pharyngeal Pouches
Paired opening located in the pharynx, behind the
mouth.
In terrestrial chordates,
these develop into the jaw,
inner ear, and tonsils.
In aquatic chordates, these develop into gill slits.
Postanal Tail
A tail that extends beyond the anus.
All chordates have a postanal tail at some
point in their development – even humans!
Muscle blocks controlling the tail are
connected to the notochord.
Subphylum Vertebrata
Includes:
• FISH
• AMPHIBIANS
• REPTILES
• BIRDS
• MAMMALS
Over 50,000 species
Subphylum Vertebrata
All Vertebrates share
• A vertebral column – replaces the
notochord during embryonic development
• Epidermis is divided into OUTER and
INNER layer –often modified to produce
hair, scales, feathers, glands, horns
• Endoskeleton – bony or cartilaginous
Subphylum Vertebrata
• Muscles attached to endoskeleton to
provide movement
• Digestive system with digestive glands,
liver and pancreas
• 2 – 4 chambered heart
• Well-developed coelom
• Paired kidneys
Subphylum Vertebrata
• Two sexes with paired gonads
• Head, trunk, two pairs of appendages, and
post-anal tail
Myers, P. 2001. "Vertebrata" (On-line), Animal Diversity Web. Accessed May 11, 2009 at
http://animaldiversity.ummz.umich.edu/site/accounts/information/Vertebrata.html.
FISH
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4 CLASSES:
Hagfishes
Lampreys
Cartilaginous Fishes
Bony Fishes
FISH
All fish:
• Breathe using gills
• Have 2-chambered
hearts
• Reproduce sexually
• Have developed
sensory systems
Most fish (cartilaginous
and bony):
• Have paired fins
• Have scales
Most fish are BONY
fish.
FISH
Jaws evolved in fish.
• can grab and crush prey
• can prey on variety of organisms
Phylum Chordata
Subphylum Vertebrata
Class Amphibia
AMPHIBIANS
Class Amphibia (amphibia = “double life”)
3 Orders:
• Caudata (salamanders and newts)
• Anura (frogs and toads)
• Apoda (legless caecilians)
AMPHIBIANS
• Adults are terrestrial, but rely on water for
reproduction
• Fertilization is external
• Ectotherms – body temp is variable
• Undergo metamorphosis
• 3-chambered hearts, skin is more
important for gas exchange – must stay
moist
Amphibians
Amphi – double;
frogs, toads, caecilians,
salamanders
• Thin, moist skin
• 4 legs
• terrestrial, but
closely tied to
water
Amphibians
• both internal and external
fertilization
• eggs lack protective
• membrane and shell –
need water to prevent
dessication.
red eye tree frog eggs
http://nationalzoo.si.edu/Animals/Rep
tilesAmphibians/Exhibit/Topics/zoo_b
reeding.cfm?inc=o
Ectotherms
• body temperature is dependent on
environmental temperature
• become dormant during times of year
when it is too hot or too cold - estivate
Metamorphosis
Metamorphosis in
frogs
Herbivorous tadpoles hatch with internal gills
• increase in mouth and tongue size
• loss of gills / formation of lungs
• growth of legs, resorption of tail
• new visual pigment in eyes
• hemoglobin protein in blood
• insectivorous adult
Metamorphosis in salamanders
• young aquatic salamanders have gills
and a tail fin
• adults do not have gills or fins – breathe
through skin or with lungs
Metamorphosis in salamanders
Some salamanders do not have larval stage,
but hatch as small versions of adults
Circulatory System
• 3-chambered heart
• one chamber gets oxygen rich blood from
lungs
• one chamber gets oxygen poor blood from
body tissues
• blood from both go to third chamber –
blood goes to body tissues and skin
Order Anura
Frogs and Toads
Frogs
• smooth, moist skin
• long legs
Toads
• bumpy, dry skin
• short legs
Both are tailless and
insectivorous
Order Anura
Frogs and Toads
• vocal cords capable of producing a wide range
of sounds.
• Vocal cords are sound-producing bands of
tissue in the throat.
Order Caudata
Salamanders
• long, slender body with a neck and tail.
• smooth, moist skin
• lack claws
• a few cm to 1.5 m
• carnivorous
Order Apoda
Caecilians
• burrowing amphibians, have no limbs, and
have a short, or no, tail.
• primarily tropical animals with small eyes
that often are blind.
• eat earthworms and other invertebrates
found in the soil.
• have internal fertilization.
Origins of Amphibians
• Most likely, amphibians arose as their
ability to breathe air through well-developed
lungs evolved.
• The success of inhabiting the land depended
on adaptations that would provide support,
protect membranes involved in respiration,
and provide efficient circulation.
Origins of Amphibians
• Amphibians first appeared about 360
million years ago.
• Amphibians probably evolved
from an aquatic tetrapod around
the middle of the Paleozoic Era.
Challenges to life on land
• Land life for amphibians held many dangers.
• Unlike the temperature of water, which
remains fairly constant, air temperatures
can vary greatly.
• In addition, without the support of water,
the body was clumsy and heavy.
Challenges to life on land
• Able to breathe through their lungs,
gills, or skin, amphibians became, for a
time, the dominant vertebrates on land.
REPTILES
Class Reptilia
4 Orders
• Squamata (snakes and lizards)
• Chelonia (turtles)
• Crocodilia (alligators and crocodiles)
• Rhynochocephalia (Tuataras)
REPTILES
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Reptiles have SCALY SKIN
Reproduce on land – AMNIOTIC EGG
Legs are more directly UNDER the body
4-chambered hearts
Ectotherms
BIRDS
Class Aves
• 8600 species of modern birds
• Inhabit variety of habitats:
Antarctica
Deserts
Tropical Rain Forests
All birds have WINGS, but not all birds FLY!
BIRDS
All birds have FEATHERS and WINGS
Feathers
• modified protein
scale
• molting – shedding
of old feathers and
growth of new
feathers
• wing and tail
feathers lost in pairs
to maintain balance
Wings
• adaptation for flight
• flight muscles
attached to sternum
(breast bone)
BIRDS
Flying requires LOTS of energy!
• 4-chambered heart beats very fast
(chickadee = 500 times/minute)
• respiratory system includes air sacs –
oxygenated air is circulated during
INHALATION and EXHALATION.
BIRDS
• ENDOTHERMS – maintain own body
temperature, independent of
environmental temperature
• Reproduction – internal fertilization,
shelled amniotic egg
Phylum CHORDATA
Subphylum VERTEBRATA
Class MAMMALIA
MAMMALS!
Class Mammalia
• Endotherms
• Produce milk for
young
• Hair
• Diaphragms
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4-chambered heart
Specialized teeth
Modified limbs
Highly developed
brains
MAMMALS!
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Hair is
made out of keratin (like feathers)
developed from scales (like feathers)
arrangement provides insulation /
waterproofing
conserves body heat (endotherms)
MAMMALS!
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Endotherms maintain constant body
temperatures
panting (release heat)
sweating (release heat)
shivering (generate heat)
raising hair (conserving heat)
MAMMALS!
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Mammals have several types of
GLANDS
Scent
Saliva
Hormones
Milk
Digestive enzymes
MAMMALS!
Mammals nurse their young
• Mammary glands – secrete milk that is rich
in fats, sugars, proteins, vitamins, and
minerals
• This continues until offspring are able to
eat and digest solid food
MAMMALS!
The diaphragm aids in breathing
• muscle beneath the lungs, separating the
THORACIC (chest) cavity from the
ABDOMINAL cavity
• Expands the chest cavity, bringing in air
• Contracts and pushes air out
MAMMALS!
Mammals have a 4-chambered heart
• Left and Right Atrium
• Left and Right
Ventricle
• Oxygenated and
deoxygenated blood
are entirely
separated.
Circulation removes
waste and maintains
HOMEOSTASIS
MAMMALS!
Mammalogists love teeth!
• you can tell what an animal eats based on
its type of teeth
• teeth are adapted to type of food eaten
• teeth are hard and fossilize more often
than other parts of the body
MAMMALS!
MAMMALS!
This mole’s pointed incisors are used to
grasp and hold small prey
MAMMALS!
A beaver’s incisors
are modified for
gnawing and can
gnaw through
almost anything.
These teeth
continue growing
throughout the
animal’s lifetime.
MAMMALS!
A lion’s sharp
canines are perfect
for slicing and
tearing flesh.
MAMMALS!
Premolars and molars are used for slicing,
shearing, crushing, and grinding.
MAMMALS!
Other characteristics include
• modified limbs
• complex behaviors – learning and
remembering
MAMMALS!
Mammals have complex brains
• Primates (including humans) are possibly
most intelligent
• use tools
• communicate
MAMMALS!
3 Orders of Mammals
• Monotremes (platypus and echidnas)
• Marsupials (kangaroos and oppossums)
• Placental Mammals (Chiroptera- bats;
Rodentia – rodents; Carnivora – weasels,
skunks, bears, foxes; Cetacea- whales,
dolphins; Primates- chimps, apes,
monkeys, humans)
MAMMALS!
Monotremes
• Eggs
• Only 3 species alive today (1 platypus,
2 echidnas)
• Found only in Australia and New
Zealand
Flat tail,
duck beak,
webbed feet
Coarse brown hair, covered in
spines
MAMMALS!
Marsupials
• short period of development in mother’s
body
• period of development inside pouch
• most are found in Australia – opossum is
North American marsupial
MAMMALS!
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Placental Mammals
Over 4000 species (mostly bats and
rodents)
Young develop in the UTERUS
Nourished by a PLACENTA
Development inside the mother’s body
ensures protection from predators and
environment during development.
MAMMALS!
The placenta is derived from the same
membranes that surround embryos in
amniotic eggs (reptiles and birds)
Marsupials also have PLACENTAE, but is
short-lived
MAMMALS!
• smallest mammals are shrews and bats
and weigh as little as 3 grams
• largest is the blue whale –
160,000 kg! (352,739 lbs!)
Origin of Mammals
• The first placental mammals appeared in the
fossils record about 125 million years ago.
• Scientists trace the
origins of placental
mammals from a
group of mouse-sized
animals to a group of
reptilian ancestors
called therapsids.
Origin of Mammals
• Therapsids had features of both reptiles and
mammals.
• They existed between 270 and 180 million years
ago.
Origin of Mammals
• The mass extinction of the dinosaurs at the
end of the Mesozoic Era, along with the
breaking apart of Pangaea and changes in
climate, opened up new niches for early
mammals to fill.
• The Cenozoic Era (65 million years to present) is
sometimes called the golden age of mammals
because of the dramatic increase in their
numbers and diversity.