Phylum Chordata 09 June 2015Chordata.ppt1. 09 June 2015Chordata.ppt 2 Phylum Chordata Latin: with a cord, = notochord Notochord Dorsal nerve cord Pharyngeal

Phylum Chordata

09 June 2015 Chordata.ppt 1


Phylum Chordata

• Phylum Chordata• Latin: with a cord, = notochord

• Notochord

• Dorsal nerve cord

• Pharyngeal arches/clefts • bear gills in fishes,

• modified to other structures in terrestrial animals

• Post-anal tail


Phylum Chordata

• Phylum Chordata• Subphylum Urochordata (= tunicates)

• Subphylum Cephalochordata (= lancelets)

• Subphylum Vertebrata


Invertebrate Chordates

• Two Subphyla of Chordata, lack distinguishing characters of Vertebrata:

Subphylum Urochordata • tunicates, sea squirts

Subphylum Cephalochordata • lancelets, amphioxus

Subphylum Urochordata

• Adults (= tunicates)• Sessile filter feeders

• Ciliated pharynx

• NO notochord

• Ganglion between siphons, but NO nerve cord


Subphylum Urochordata


• Larva• “tadpole larva”

exhibits characters of Chordata

• Notochord

• Pharyngeal arches

• Dorsal nerve cord

• Post-anal tail


Subphylum Cephalochordata“lancelets”

Subphylum Cephalochordata“lancelets”

• Adults & larvae• Filter feeders

• Ciliated tentacles and pharynx • Filtered food passes into intestine

• Gas exchange through epidermis • Pharnygeal arches are NOT “gills”



Phylum Chordata

• Subphylum Vertebrata• Notochord reduced, replaced by bony or

cartilaginous vertebrae• Some notochord tissue usually remains

• Pharyngeal arches bear gills • or developed into other organs: hyoid bone, larynx

• Liver

• Pancreas


Phylum Chordata

• Subphylum Vertebrata• Classes (?):• Jawless fishes

• Cartilaginous fishes

• Ray-finned (Bony) fishes (Actinopterygii)

• Lobe-finned fishes (Sarcopterygii)

• Amphibians

• Reptiles, including Birds

• Mammals


Subphylum Vertebrata

“Fishes”


Fishes

• Aquatic & Marine fishes retain four (4) primitive characters:• Streamlined body

• Vertical tail fin

• Gills for gas exchange

• Lateral line system, • No ears


“Jawless Fishes”

• Survivors of earliest vertebrates• No jaws, • can not close mouth

• No scales• No paired fins, only median tail fin (continues

dorsal & ventral to anus)• Single median nostril on top of head • Circular gill slits • 7 or 12 pairs on sides of pharynx.


Myxini, Hagfishes

• Hagfishes • Rudimentary head

skeleton

• No true vertebrae

• tentacles around mouth

• predators on worms, mollusks

• scavengers

• 20 spp. in 4 genera


Petromyzonida, Lampreys

• Lampreys • circular mouth with

“horny” teeth,

• Rings of cartilage around notochord • = vertebrae

• filter feeders, or

• external parasites of bony fishes

• 30 spp. in 10 genera


Development of Jaws• Jaws developed from gill arch,• Maxilla (upper)

• Mandible (lower)

• Allowed diverse diet: herbivores, predators

• Hyoid arch developed from second arch


Class Chondrichthyes

• About 750 species • Skeleton of cartilage, bone lost.

Fossil placoderms and jawless fishes had bone tissue, prob. ancestral to both Cartilaginous & Bony fishes.


Class Chondrichthyes

• Cartilaginous skull poorly developed, esp. dorsal to brain

• Fins supported by cartilage or horn-like rays


Cartilaginous Fishes

• No ribs.• No lungs or swim bladder.• Separate gill slits, usually 5• Placoid scales,

• tiny, tooth-like

• Enlarged at edge of mouth teeth • Homologous to teeth in all

later vertebrates.

• Marine• Retain urea for

osmoregulation


“Bony Fishes”

• ~30,000+ species. • Majority of living vertebrate species. • Bony skeleton, well developed skull,• Fins supported by cartilage or bony “rays”

and minute scales, • Or, “fins” developed into “limbs.”


“Bony Fishes”• Diversification of “bony

fishes”• Most remain “fishes”

(Actinopterygii)• Sarcopterygii developed strong

bones and muscle in fin bases• Able to “walk” on land

• Dipnoi adapted to intermittent streams, stagnant pools

• Tetrapods adapted to move well on land.


Class Actinopterygii

• Bony dermal scales• covered by thin

epidermis• NOT homologous to

reptilian scales.

• Operculum covers gills; one gill slit each side.

• Lungs, often modified to swim bladder.

Class Actinopterygii

• Examples: • sturgeons• gars• catfish• trout• bass• Northern pike• American eel

• note paired fins, jaw, operculum



Actinistia & Dipnoi

• Actinistia• Rhipidistians extinct

• Coelocanths thought extinct until 1938• Western Indian Ocean

• Newly discovered population in Indonesian waters

• Dipnoi (“2 lungs”)• Australian and African

lungfishes


Tetrapods

• Adapted to move easily and efficiently on land• Loss of fin tissue on

limbs

• Digits (5 per limb)

• Longer, stronger limbs• Lift belly off of ground


Class Amphibia• Old group of tetrapod (4-footed) vertebrates,

older than reptiles.• Origin in mid-Paleozoic (Carboniferous period)


Class Amphibia

• Less well adapted to terrestrial environment

• Smooth skin, no scales (no keratin ?)

• External fertilization• depend on water for mating; sperm and eggs

released together into water

• No embryonic membranes,

• Egg must stay moist • usually in water, rarely in moist soil


Amphibian Life Cycle

• Larvae (immature form, tadpoles) hatch in water, • Gills for gas exchange.

• Tail

• Metamorphosis to adult form • growth of limbs

• development of lungs and loss of gills

• loss of tail in frogs, toads

• Adult usually terrestrial, some exceptions


Class Amphibia• Order Urodela (Salamanders)

Primitive form with four equal legs Retain tail


Class Amphibia• Order Anura (Frogs)

Tail lost in metamorphosis Hind legs enlarged, hopping or leaping locomotion


Class Reptilia


Class Reptilia• Old group of tetrapod (4-footed) vertebrates• Origin in Carboniferous; Diverse in Permian (end

of Paleozoic)


Class Reptilia

• Successful terrestrial vertebrates • Ancestral fishes and amphibians incompletely

adapted to land• A few fishes can survive out of water for several hours

• Lungfishes survive droughts of several months

• Amphibian adults live on land, but must mate & lay eggs in water

• Most reptiles never go into the water.

Reptiles’ success

• 3 adaptations to terrestrial environmentKeratinized skin

• epidermal scales • reduce water loss

• abrasion resistant

Internal fertilization• Sperm deposited in

female body

Amniote egg


Amniote egg

• Embryo develops membranes within shell• amnion, chorion, yolk

sac, allantois

• Shell permeable to air (breathes)

• Amnion, chorion retain water to keep embryo wet.



Modern Reptiles

• traditional Class Reptilia

• Retain primitive characters• Epidermal scales of keratin

• also: hair in mammals, feathers in birds, scales on bird’s feet

• Five toes per foot with claws (derived from scales).


Modern Reptiles: Diapsids

• Order Lizards (includes Snakes)• Forked tongue• Fracture plane in tail (lost in snakes ?)• Paired hemipenes in males


Modern Reptiles: Anapsids

• Order of turtles• 200+ species

• Bony plates form shell

• carapace

• plastron


Modern Reptiles: Diapsids• Two holes in “bony roof”• Order Crocodilians• Hard palate (differs from mammal’s)• Tongue fused to lower jaw• Ball-and-socket joints between trunk vertebrae


Reptiles: Diapsids

• Two holes in “bony roof”

• Order Dinosaurs

• Suborder Ceratopsians

• Suborder Duckbilled dinos.

• Suborder Sauropods

• Suborder Theropods

• Include Birds

Documents

Phylum Chordata 09 June 2015Chordata.ppt1. 09 June 2015Chordata.ppt 2 Phylum Chordata Latin: with a cord, = notochord Notochord Dorsal nerve cord Pharyngeal