Phylum Chordata
General Characteristics and
Phylogeny
Basic Chordate Characters
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notochord
dorsal hollow nerve cord
postanal tail
segmental muscles
pharyngeal slits and bars
(ventral heart)
A Simple Chordate (Amphioxus)
compare Hickman p. 273-274
Chordate Locomotion
• Notochord stiffens the long body axis
– pressurized cartilage material bound in fibrous
sheath
• segmental muscles (myomeres) act on
notochord to produce undulating motion
• dorsal nerve cord branches to each set of
muscles to coordinate swimming motion
• postanal tail and caudal fin add power
Chordate Feeding
• Basic pattern is filter-feeding
– Water passing through pharyngeal slits
is strained by bars between them.
– Cilia move food particles trapped in
mucus on pharyngeal bars along ventral
and dorsal tracks to stomach
– Pharyngeal slits and bars are metameric
Chordate Examples
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sea squirts, lancelets, lamprey eels
sharks, rays, trout, bass, tuna
lungfish, frogs, salamanders
snakes, lizards
turtles, crocodiles, dinosaurs, birds
mice, elephants, whales, dogs, people
Chordate Subphyla
Urochordata, Cephalochordata,
and Introduction to Craniata,
Snot otter stories
Common Names
• Urochordata
– sea squirts, salps, larvaceans
• Cephalochordata
– lancelets
• Craniata
– hagfishes, lampreys, fishes, etc.
subphylum Urochordata
“notochord in the tail”
• only the larvae have full chordate
characters
– adults greatly modified
– pharynx with slits is main character
• adults are sessile or planktonic filterfeeders
Urochordata Tadpole Larva
Hickman Fig. 14-6
Sea Squirt Metamorphosis
Hickman Fig. 14-6
myomeres
Sea Squirt Anatomy
(adult)
Hickman Fig. 14-5
subphylum Cephalochordata
“notochord in the head”
• notochord goes farther forward
• similar to ancestor of craniates
– and fossils from Burgess Shale
• benthic suspension feeders
• few species, but sometimes abundant
Cephalochordata Anatomy
gonads
Hickman Fig. 14-8
lancelet, or
amphioxus
Craniata
• phylum Chordata
• subphylum Craniata
– hagfishes (class name not required)
• between subphylum and class - Vertebrata
– lampreys (class name not required)
– other fishes and tetrapods
Jawless Craniates
Hickman Fig. 15-3
hagfish
lamprey eels, on carp
Chondrichthyes Examples
black-tip reef shark
manta ray
blue-spotted sting ray
Shark Advances over Lampreys
• jaws
– from pharyngeal arches
• bony skin plates
– evolved to fish scales and teeth
• pectoral and pelvic arches and fins
Bony fishes
• swim bladder
– enabling bony skeleton, variable body
forms
• operculum
– to force water over gills
• fin skeletal support
– for increased maneuverability
• terminal, complex mouth
External Anatomy
operculum
lateral line
terminal
mouth
pectoral fin
pelvic fin
homocercal tail
Internal Anatomy
Hickman Fig. 15-13
Amphibians
• “living a double life”
Have aquatic and terrestrial
adaptations
• Eggs
– fertilized in water, no shell, covered
with gelatin
• Aquatic larva
– Tail, lateral line, gills, no legs
Salamanders
Tail!
walking is awkward;
legs out on sides of
body
Frogs and Toads
Tail lost!
ribs and neck
reduced, hind legs
enlarged
• communicate with
sound
Reptiles
Turtles, Snakes, Lizards, and
Crocodiles
nostril
pit organ
hollow fang
poison gland
glottis
Reptilian adaptations
• Keratin covered scales
“waterproofed”
• Eggs with shells that retain water
– Amniotic egg
• Ectothermic - do not use metabolism
to alter body temperature
Amniontic egg
Has 4 membranes
• amnion
• allantoi
s
• yolk
sac
• chorion
Reptile groups
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Lizards
Turtles
Crocodiles and alligators
Snakes
Examples of Lizards
Komodo
dragon
iguana
Examples of Snakes
compare Campbell Fig. 18.20
garter
snake
coral snake
olive sea
snake
timber rattlesnake
Crocodilia
American
crocodile
not an alligator:
narrow snout,
large lower tooth
exposed with
mouth closed
Turtles
freshwater
carapace
terrestrial
marine
plastron
Birds
• Amniotic eggs, scales on legs, keratin
• Feathers
• Reduced skeleton and large muscles
for flying
• Special lungs and circulatory system
• Endothermic – make their own heat
Mammals
Basic Features of the Class
Mammal Adaptations
• endothermy, hair, sweat and scent
glands
• varying teeth (“heterodont”),
epiglottis
• improved olfaction, larger nasal cavity
• 4-chambered heart, diaphragm
• more coordination, acute senses, and
learning ability
Oviparous Mammals
• 3 species in one order Monotremata
– all live in Australia or New Guinea
• lay eggs, but have hair and nurse
young
Campbell Fig. 18.22 (a)
duck-billed platypus
mother, nursing
Marsupial Mammals
• fetuses do not fully implant in the
simpler uterus
• adult females have a belly pouch
(marsupium)
– newborns stay inside, attached to nipple,
for months
Marsupial Mammals
Campbell Fig. 18.22B
South American
tree opossum
North American opossum
Australian kangaroo
Placental Mammals
• true placenta formed by fetus and
mother
• Joins the embryo to the mother
within the mother’s uterus
• Embryo is nurtured by blood from the
mother
• 95% of all mammals
Placental mammals