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09 June 2015 Chordata.ppt 2
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
09 June 2015 Chordata.ppt 3
Phylum Chordata
• Phylum Chordata• Subphylum Urochordata (= tunicates)
• Subphylum Cephalochordata (= lancelets)
• Subphylum Vertebrata
09 June 2015 Chordata.ppt 4
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
09 June 2015 Chordata.ppt 5
Subphylum Urochordata
09 June 2015 Chordata.ppt 6
• Larva• “tadpole larva”
exhibits characters of Chordata
• Notochord
• Pharyngeal arches
• Dorsal nerve cord
• Post-anal tail
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”
09 June 2015 Chordata.ppt 8
09 June 2015 Chordata.ppt 9
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
09 June 2015 Chordata.ppt 10
Phylum Chordata
• Subphylum Vertebrata• Classes (?):• Jawless fishes
• Cartilaginous fishes
• Ray-finned (Bony) fishes (Actinopterygii)
• Lobe-finned fishes (Sarcopterygii)
• Amphibians
• Reptiles, including Birds
• Mammals
09 June 2015 Chordata.ppt 12
Fishes
• Aquatic & Marine fishes retain four (4) primitive characters:• Streamlined body
• Vertical tail fin
• Gills for gas exchange
• Lateral line system, • No ears
09 June 2015 Chordata.ppt 13
“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.
09 June 2015 Chordata.ppt 14
Myxini, Hagfishes
• Hagfishes • Rudimentary head
skeleton
• No true vertebrae
• tentacles around mouth
• predators on worms, mollusks
• scavengers
• 20 spp. in 4 genera
09 June 2015 Chordata.ppt 15
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
09 June 2015 Chordata.ppt 16
Development of Jaws• Jaws developed from gill arch,• Maxilla (upper)
• Mandible (lower)
• Allowed diverse diet: herbivores, predators
• Hyoid arch developed from second arch
09 June 2015 Chordata.ppt 17
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.
09 June 2015 Chordata.ppt 18
Class Chondrichthyes
• Cartilaginous skull poorly developed, esp. dorsal to brain
• Fins supported by cartilage or horn-like rays
09 June 2015 Chordata.ppt 19
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
09 June 2015 Chordata.ppt 20
“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.”
09 June 2015 Chordata.ppt 21
“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.
09 June 2015 Chordata.ppt 22
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
09 June 2015 Chordata.ppt 23
09 June 2015 Chordata.ppt 24
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
09 June 2015 Chordata.ppt 25
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
09 June 2015 Chordata.ppt 26
Class Amphibia• Old group of tetrapod (4-footed) vertebrates,
older than reptiles.• Origin in mid-Paleozoic (Carboniferous period)
09 June 2015 Chordata.ppt 27
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
09 June 2015 Chordata.ppt 28
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
09 June 2015 Chordata.ppt 29
Class Amphibia• Order Urodela (Salamanders)
Primitive form with four equal legs Retain tail
09 June 2015 Chordata.ppt 30
Class Amphibia• Order Anura (Frogs)
Tail lost in metamorphosis Hind legs enlarged, hopping or leaping locomotion
09 June 2015 Chordata.ppt 32
Class Reptilia• Old group of tetrapod (4-footed) vertebrates• Origin in Carboniferous; Diverse in Permian (end
of Paleozoic)
09 June 2015 Chordata.ppt 33
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
09 June 2015 Chordata.ppt 34
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.
09 June 2015 Chordata.ppt 35
09 June 2015 Chordata.ppt 36
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).
09 June 2015 Chordata.ppt 37
Modern Reptiles: Diapsids
• Order Lizards (includes Snakes)• Forked tongue• Fracture plane in tail (lost in snakes ?)• Paired hemipenes in males
09 June 2015 Chordata.ppt 38
Modern Reptiles: Anapsids
• Order of turtles• 200+ species
• Bony plates form shell
• carapace
• plastron
09 June 2015 Chordata.ppt 39
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
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