The ChordatesThe Chordates

Chapters 30-32Chapters 30-32

BiologyBiology – Miller – Miller • Levine• Levine

ChordatesChordates

• Phylum Phylum ChordataChordata

• Includes two Includes two invertebrate invertebrate subphyla: subphyla: lanceletslancelets and and tunicatestunicates

• Subphylum Subphylum VertebrataVertebrata

Chordate CharacteristicsChordate Characteristics

• Dorsal, hollow nerve cordDorsal, hollow nerve cord – the – the brain and spinal cord brain and spinal cord

• NotochordNotochord – flexible, longitudinal rod – flexible, longitudinal rod located between the digestive tract located between the digestive tract and the nerve cord and the nerve cord

• Pharyngeal pouchesPharyngeal pouches – gill – gill structures in the pharynx structures in the pharynx

• PostPost--anal tailanal tail – tail to the rear of the – tail to the rear of the anus anus

Chordate CharacteristicsChordate Characteristics

• The characteristics are not always The characteristics are not always visible in the adult form, but are visible in the adult form, but are always present in the embryo always present in the embryo

VertebratesVertebrates

•Subphylum that includes Subphylum that includes mammals, birds, reptiles, mammals, birds, reptiles, amphibians and the various amphibians and the various classes of fishes classes of fishes

•Unique features include cranium Unique features include cranium and backboneand backbone

FishesFishes

AgnathansAgnathans• Jawless fishJawless fish

• ClassClass Myxini Myxini (hagfishes)(hagfishes)

• Class Class CephalaspidomorphiCephalaspidomorphi (lampreys)(lampreys)

Class ChondrichthyesClass Chondrichthyes

•Cartilaginous fishesCartilaginous fishes

• Include sharks and raysInclude sharks and rays

•Have a flexible skeleton made of Have a flexible skeleton made of cartilage cartilage

•Lateral line systemLateral line system – row of – row of sensory organs running along sensory organs running along each side of the body, detects each side of the body, detects minor vibrations minor vibrations

Class ChondrichthyesClass Chondrichthyes

Class OsteichthyesClass Osteichthyes

•Bony fishes (trout and goldfish) Bony fishes (trout and goldfish)

•Also have a lateral line system Also have a lateral line system

•OperculumOperculum – protective flap – protective flap that covers the gills that covers the gills

•Swim bladderSwim bladder – gas-filled sac – gas-filled sac that keeps them buoyantthat keeps them buoyant

Class OsteichthyesClass Osteichthyes• Most are Most are ray-finned fishesray-finned fishes – fins – fins

supported by thin, flexible rays supported by thin, flexible rays • LungfishesLungfishes – must surface to gulp air – must surface to gulp air

into their lungs into their lungs • LobeLobe--finned fishesfinned fishes – fins are – fins are

supported by stout bonessupported by stout bones

AmphibiansAmphibians

Class AmphibiaClass Amphibia

•Frogs and salamandersFrogs and salamanders

•Exhibit a mixture of aquatic & Exhibit a mixture of aquatic & terrestrial adaptations terrestrial adaptations

•Need water to reproduce Need water to reproduce

•Depend on their moist skin to Depend on their moist skin to supplement lung function in supplement lung function in exchanging gases exchanging gases

Class AmphibiaClass Amphibia

• First vertebrates to colonize land First vertebrates to colonize land

• TetrapodsTetrapods (“four legs”) – terrestrial (“four legs”) – terrestrial vertebrates (amphibians, reptiles, vertebrates (amphibians, reptiles, birds & mammals) birds & mammals)

ReptilesReptiles

Class ReptiliaClass Reptilia•Snakes, lizards, turtles, crocodiles, Snakes, lizards, turtles, crocodiles,

and alligatorsand alligators

•Have many additional adaptations Have many additional adaptations for living on land for living on land

•Water-proofed scales to prevent Water-proofed scales to prevent dehydration dehydration

•Amniotic eggAmniotic egg – water-containing – water-containing egg enclosed in a shellegg enclosed in a shell

Class ReptiliaClass Reptilia• EctothermsEctotherms – warms itself by – warms itself by

absorbing external heatabsorbing external heat – Can survive on less than 10% of the Can survive on less than 10% of the

calories required by mammals calories required by mammals

• Mesozoic era – “age of reptiles” – the Mesozoic era – “age of reptiles” – the time of the dinosaurstime of the dinosaurs

BirdsBirds

Class AvesClass Aves

•BirdsBirds•Reptilian Reptilian

features – features – scales on legs, scales on legs, amniotic egg amniotic egg

•Almost all Almost all species are species are able to fly able to fly

Class AvesClass Aves

•Adaptations for flight:Adaptations for flight:– Light, hollow bone Light, hollow bone – Absence of some internal organs Absence of some internal organs – Are toothless Are toothless – EndothermsEndotherms – maintain – maintain

temperature using metabolic heat temperature using metabolic heat – Wings – strong muscles, feathers Wings – strong muscles, feathers

MammalsMammals

Class MammaliaClass Mammalia

•Probably evolved from reptilesProbably evolved from reptiles•Most are terrestrial, some are Most are terrestrial, some are

aquatic (dolphins, whales), some aquatic (dolphins, whales), some can fly (bats) can fly (bats)

•Two unique features: hair and Two unique features: hair and mammary glands mammary glands

•Are endotherms Are endotherms •Have a fluid filled amniotic sacHave a fluid filled amniotic sac

Three Major GroupsThree Major Groups

• MonotremesMonotremes – egg-laying mammals – egg-laying mammals (platypus) (platypus)

• MarsupialsMarsupials – pouched mammals – pouched mammals (kangaroo) (kangaroo)

• EutheriansEutherians – placental mammals – placental mammals– Make up almost 95% of mammalsMake up almost 95% of mammals

• Marsupials and Eutherians both have a Marsupials and Eutherians both have a placentaplacenta which joins the embryo to the which joins the embryo to the mother and provides nutrients to the mother and provides nutrients to the embryo embryo

Class MammaliaClass Mammalia

PrimatesPrimates

•Order that includes monkeys, apes Order that includes monkeys, apes & humans & humans

•Early primates were small, Early primates were small, arboreal (tree-dwelling) mammalsarboreal (tree-dwelling) mammals – Limber shoulder joints, dexterous Limber shoulder joints, dexterous

hands, eyes close together on face, hands, eyes close together on face, excellent hand-eye coordinationexcellent hand-eye coordination

PrimatesPrimates• Divided into two main groups: Divided into two main groups:

– ProsimiansProsimians (lemurs) (lemurs) – AnthropoidsAnthropoids (monkeys, apes & humans) (monkeys, apes & humans)

• Humans are most closely related to apes Humans are most closely related to apes