Vertebrates

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Slide 1

Half a Billion Years of Backbones

Early in the Cambrian period, about 530 million years ago, an astonishing variety of animals inhabited Earth’s oceans.

One type of animal gave rise to vertebrates, one of the most successful groups of animals.

The animals called vertebrates get their name from vertebrae, the series of bones that make up the backbone.

There are about 52,000 species of vertebrates, including the largest organisms ever to live on the Earth.

Slide 2

Are humans among the descendants of this ancient organism?

Slide 3

Concept 34.1: Chordates have a notochord and a dorsal, hollow nerve cord

Vertebrates are a subphylum within the phylum Chordata.

Chordates are bilaterian animals that belong to the clade of animals known as Deuterostomia.

Two groups of invertebrate deuterostomes, the urochordates and cephalochordates, are more closely related to vertebrates than to other invertebrates.

Slide 4

Phylogeny of living chordates

Lobed fins

Legs

Amniotic egg

Milk

Jaws, mineralized skeleton

Lungs or lung derivatives

Vertebral column

Head

Notochord

Common

ancestor of

chordates

ANCESTRAL

DEUTERO-

STOME

Echinodermata

(sister group to chordates)

Chondrichthyes

(sharks, rays, chimaeras)

Cephalochordata

(lancelets)

Urochordata

(tunicates)

Myxini

(hagfishes)

Petromyzontida

(lampreys)

Mammalia

(mammals)

Actinopterygii

(ray-finned fishes)

Actinistia

(coelacanths)

Amphibia (frogs,

salamanders)

Dipnoi

(lungfishes)

Reptilia

(turtles, snakes,

crocodiles, birds)

Chordates

Craniates

Vertebrates

Gnathostomes

Lobe-fins

Osteichthyans

Tetrapods

Amniotes

Slide 5

Derived Characters of Chordates

All chordates share a set of derived characters.

Some species have some of these traits only during embryonic development.

Four key characters of chordates:

Notochord

Dorsal, hollow nerve cord

Pharyngeal slits or clefts

Muscular, post-anal tail

Slide 6

Chordate characteristics

Dorsal,

hollow

nerve cord

Anus

Muscular,

post-anal tail

Pharyngeal

slits or clefts

Notochord

Mouth

Muscle

segments

Slide 7

Notochord