19 chap 23 chordata

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