19 chap 23 chordata
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Phylum Chordata
General Characteristics and Phylogeny
Basic Chordate Characters
• 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
• 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 filter-feeders
Urochordata Tadpole Larva Hickman Fig. 14-6
Sea Squirt MetamorphosisHickman 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 AnatomyHickman Fig. 14-8
lancelet, or amphioxus
gonads
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 CraniatesHickman Fig. 15-3
hagfish lamprey eels, on carp
Chondrichthyes Examplesblack-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
operculumlateral line
homocercal tailpectoral fin pelvic fin
terminal mouth
Internal AnatomyHickman 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
Turtles, Snakes, Lizards, and Crocodiles
Reptiles
nostrilpit organ
poison gland
glottis
hollow fang
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
• Lizards• Turtles• Crocodiles and alligators• Snakes
Examples of Lizards
iguana
Komodo dragon
Examples of Snakescompare Campbell Fig. 18.20
coral snake
olive sea snake
garter snake
timber rattlesnake
Crocodilia
American crocodile
not an alligator:
narrow snout, large lower tooth exposed with mouth closed
Turtlesplastron
carapace terrestrial
freshwater
marine
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
MammalsBasic 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 MammalsCampbell Fig. 18.22B
North American opossum
South American tree 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