PHYLUM CHORDATA

“Our Phylum”

Subphylum Urochordata

Subphylum Cephalochordata

Subphylum Vertebrata

“Pre-Cambrian”

produced only

unicellular organisms

THE CAMBRIAN EXPLOSION

All major phyla including

Phylum Chordata

Geologic Time Scale

Origin of Species

(Chapter IX)

On the Imperfection of the Geologic Record

“There is another and allied difficulty, which is

much graver. I allude to the manner in which

numbers of species of the same group , suddenly

appear in the lowest known fossiliferous rocks.”

Darwin was aware …

Explosion led to as many as 100 phyla most

of which are extinct (32 extant phyla?)

CHORDATE EXAMPLES

“DUDES”Deuterostomes

Chordates are DEUTEROSTOMES

5 CHORDATE CHARACTERISTICS

1) Notochord – present in embryonic, larval or adult stages

Not Cartilage!!

Large fluid-filled cells

having turgor pressure

CELLS

of the notochord

Embryonic Salamander

Notochord Cells

Neural Tube

x.s.

l.s.

2) DORSAL TUBULAR NERVE CORD

CHORDATE CHARACTERISTICS continued …

Chick

Gastrulation

HIGHER Central Nervous Systems remain hollow

EXAMPLE: Human Brain

Contrast to Phylum Annelida:

Ventral & Solid

Nerve Cord

Earthworm

Embryos

During pharyngeal development,

outside ectoderm invaginates …

inside endoderm evaginates

SLIT formation?

3) PHARYNGEAL POUCHES & CLEFTS

FISH?

CHORDATE CHARACTERISTICS continued …

Gill Slits: Openings that connect the pharynx to the outside

Tetrapod Vertebrates

Pouches form … but slits don’t break through.

Pouches develop into …

middle ear cavity

eustachian tube

tonsils

parathyroid glands

CHORDATE CHARACTERISTICS continued …

4) POSTANAL TAIL (advance in locomotion)

anus

OUR TAIL

Post-anal Tail + Notochord (or Vertebral

Column) + Muscles + Fins =

Propulsive Power

5) ENDOSTYLE or THYROID GLAND

CHORDATE CHARACTERISTICS continued …

Strip of tissue on the floor of the pharynx – secretes sticky mucus that

traps food from “inhaled” water.

In vertebrates, the thyroid gland develops in place of the endostyle.

The vertebrate

Thyroid Gland

Subphylum Urochordata

Subphylum Cephalochordata

Subphylum Vertebrata

All Oceans

Most Depths

1600 species

Urochordates (tunicates)

http://www.flickr.com/photos/nuytsia_pix/3130748320/

(secretes mucus)

(lined with ciliated cells)

ODD?

Closed circulatory system … BUT …

- no distinction between arteries & veins

- no capillaries

- blood flows forward & back

ODD?

*super-high tissue concentrations

of vanadium & niobium

*tunic contains cellulose

Amphioxus

Subphylum Urochordata

Subphylum Cephalochordata

Subphylum Vertebrata

29 species

THE 5

Subphylum Urochordata

Subphylum Cephalochordata

Subphylum Vertebrata

the

Tunicates use gill slits for

feeding:

Water (w/food) enters

“mouth” & exits slits