Kingdom AnimaliaPhylum Chordata“Vertebrates”

Phylum Chordata“Vertebrates

• Organisms in this phylum are segmented animals with four distinctive features• Dorsal hollow nerve cord• Stiff notochord• Pharyngeal slits behind the mouth• Muscular post-anal tail• Coelom• Bilateral symmetry

Simplest Chordates

• The simplest chordates are tunicates and lancelets.• These are marine invertebrates

POST-ANAL TAIL

DORSAL, HOLLOWNERVE CORD

PHARYNGEALSLITS

MouthMuscle

segments

NOTOCHORD

LARVA

Tunicates

Simplest Chordates

HeadNOTOCHORD

DORSAL, HOLLOWNERVE CORD

Mouth

PharynxPHARYNGEALSLITS Digestive

tract

Water exit

Segmentalmuscles

AnusPOST-ANALTAIL

Lancelets

VertebratesA skull and a backbone are hallmarks of vertebrates

• Most chordates are vertebrates.• Their

endoskeletons include a skull.

• Their backbone is composed of vertebrae.

Vertebrae Backbone Skull

VertebratesMost vertebrates have hinged jaws.

• Exception: Lampreys lack hinged jaws.• They are classified as agnathans.

• Jaws evolved by the modification of skeletal supports of the gill slits.

Gillslits

Skeletalrods

Skull

Mouth

Class ChondrichthyesCartilaginous Fish

• Fish are jawed vertebrates with gills and paired fins.• Cartilaginous fish diverged before bony skeletons

appeared.• Examples: Shark and ray

Class OsteichthyesBony fish

• Bony fishes are more diverse and have– more mobile fins– operculi that move water over the gills– a buoyant swim bladder

BONY SKELETON

SWIM BLADDERGills

OPERCULUM

Class Osteichthyes

• Three sub-classes of bony fish:• Ray-finned• Lobe-finned• Lungfish

• Evolutionary evidence suggests that tetrapods evolved from lobe-finned fish.

Rainbow trout,a ray-fin

Coelacanth,a lobe-fin

• Air-breathing lungfishes that developed skeleton-reinforced appendages probably gave rise to the first amphibians.

Bonessupporting gills

Typical tetrapod limb skeleton

Class Amphibia1st Land Vertebrates

• Class Amphibia is represented today by:• frogs• toads• Salamanders

• Their limbs allow them to move on land.• However, amphibian larvae must develop in water.

Class Amphibia

• Key Characteristics:• Body Temperature: Ectotherms – obtain their body heat

from the external environment• Reproduction: Females lay eggs in water, and males

fertilize. Eggs do not have shells or outer coverings.• Examples:• Frogs and toads• Salamanders and newts• Caecilians (worm-like animal burrows in soil)

Class Reptilia1st amniotic egg

• Reptiles have more terrestrial adaptations than amphibians.

• Class Reptilia is able to live on land due to:• waterproof scales• a shelled, amniotic egg

• Modern reptiles are still ectotherms.• They warm their bodies by

absorbing heat from the environment.

Class Aves1st Endotherms

• Class Aves has: • scales• amniotic eggs• Wings• Feathers• an endothermic

metabolism• hollow bones• a highly efficient

circulatory system

Teeth(like reptile)

Wing claw(like reptile)

Feathers

Long tail withmany vertebrae(like reptile)

Class Aves

• Birds share many characteristics in common with reptiles.

• Scientists believe that birds’ feathers are evolved scales.• Consider the scaly skin of birds’ feet.

Class Mammalia

• Mammals also evolved from reptiles.• Mammals are endothermic.• There are two unique mammalian characteristics:• Hair, which insulates the body• Mammary glands, which produce milk that

nourishes their young.

Class MammaliaMonotremes

• Monotremes: a few mammals lay eggs• Example: duck-billed platypus

Class MammaliaMarsupials

• Marsupials have a short gestation.• The tiny offspring

complete development attached to the mother’s nipple, usually inside a pouch.

• Example: kangaroos

Class MammaliaPlacental Mammals

• Most mammals are eutherians, also called placentals,• They have a relatively long

gestation.• Complete embryonic

development occurs within the mother.

Phylogeny of the Animal Kingdom

• A traditional phylogenetic tree is based on patterns of embryonic development and some fundamental structures.

Porifera Platyhelminthes Mollusca Arthropoda Chordata

EchinodermataAnnelidaNematodaCnidaria

No body cavity

Pseudocoelom PROTOSTOMESCoelom fromcell masses

DEUTEROSTOMESCoelom fromdigestive tube

True coelom

Body cavity

Bilateralsymmetry

True tissues

Ancestral protists

Radialsymmetry

No true tissues

Presentday