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I. CHORDATA
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
CHORDATE CHARACTERISTICS (present at some stage):
1. NOTOCHORD: a longitudinal, flexible rod located between the digestive tube and the nerve cord. Present in all embryos.
2. DORSAL, HOLLOW NERVE CORD: hollow nerve cord that develops into the central nervous system
3. PHARYNGEAL SLITS:
allows water to enter and
leave w/out going thru
digestive tract
4. POSTANAL TAIL:
in invertebrates digestive
tract goes to end. Tail
used for propulsion
I. CHORDATA
A. UROCHORDATA: e.g., Tunicates
http://krupp.wcc.hawaii.edu/BIOL200L/powerpnt/inverts02/img038.jpg
-sessile or planktonic marine animals.
-most are sessile that adhere to rocks, docks and boats.
-can occur singly or in colonies
I. CHORDATA
A. UROCHORDATA: e.g., Tunicates
-adults have pharyngeal slits, but
larvae have all four characteristics
of a chordate
-lost during metamorphosis
I. CHORDATA
B. Subphylum: Cephalochordates – e.g., lancelets
-has all four characteristics of chordates as adults
-known for having their posterior buried in sand, with anterior exposed for feeding
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
-feed by pumping water through pharyngeal slits, food particles filtered by mucus layer
-molecular evidence suggest this is the closest relatives of vertebrates
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
What makes a vertebrate?
The four characters of Chordates plus:
1. neural crest – embryonic tissue develops near the notochord
-cells from this give rise to unique vertebrate structures like the braincase
2. cephalization – concentration of neural and sensory equipment in the head
3. vertebral column – cartilage or bones
that protect spinal nerve cord
4. closed circulatory system
5. most also have appendicular
skeleton
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates1. Superclass AGNATHA (Jawless vertebrates)
a. Class Myxini (hagfish)
-not a true vertebrate, but do have cranium
-diverged from vert ca. 530 mya
-mostly marine scavengers
-skeleton entirely of cartilage
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates1. Superclass AGNATHA (Jawless “vertebrates”)
b. Class Cephalaspidomorphi (lampreys)
-notochord is protected by cartilagenous pipe (possibly “origin” of vertebral column)
-cartilagenous skeleton
-primarily a parasite: uses rasping mouth to break fish scale and feed on blood
-larvae typically freshwater, then move to sea/ocean as adults
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
-vertebrates with jaws (evolved from rods that support pharyngeal slits)
-started replacing jawless fishes in Devonian (ca. 350 mya) period
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
a. Class CHONDRICHTHYES (Cartilage fishes like sharks and rays)
some distinguishing characters:- two fins- endoskeleton made of cartilage not bone (but teeth are bony)- cartilagenous skeleton is derived from bony skeleton!- need to swim in order to keep buoyant (no swim bladder)
diversity:- ca. 750 species
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsChimaeriformes
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
Three classes of bony fishes: “Osteichthyes”
distinguishing characters:-ossified skeleton-presence of swim bladder
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
b. Class Sarcopterygii (Fleshy-finned fishes)
distinguishing characters: -muscular pectoral and pelvic fins, with bony support-mainly bottom dwellers
diversity:-only one species exists today: coelacanth
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
Three classes of bony fishes: Osteichthyes
c. Class Actinopterygii (ray-finned fishes): most familiar
some distinguishing characters:-fins supported by rays -modified fins that allow greater maneuverability
diversity: ca. 24,000
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I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
Three classes of bony fishes: Osteichthyes
d. Class Dipnoi (lung fishes)
some distinguishing characters:-have lungs, used to supplement gas exchange through gills-live in stagnant waters-likely lineage that gave rise to tetrapods
diversity: 6 extant species {in South America (1 species), Africa (4 species), and Australia (1 species)}
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. SuperclassGNATHOSTOMATA
Tetrapods evolved from freshwater fishes in shallow water –better to “walk” than swim in thick vegetation in water
Gill breathing supplemented by buccal breathing and lungs
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
Acanthostega, a tetrapod fish
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
e. Class AMPHIBIA (“two lives”)- Carboniferous (ca. 350 mya)
some distinguishing characters:- four limbs- amphibia refers to having a water and land stage (many amphibians do
this). Most are tied to water for reproduction- Many use moist skin for breathing- eggs lack a shell
diversity:- ca 4800 species
http://www.coestatepark.com/california_newt.htm
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
Amniota:
1. amniotic egg2. water-proof skin (keratin)3. evolved rib cage for lungs
lung used exclusivelyfor gas exchange (exceptsome turtles)
-allowed for better invasionof land; no longer tiedto water
evolved ca. 250 mya (Mesozoic)
I. CHORDATA
C. Subphylum: Vertebrata –vertebrates
2. SuperclassGNATHOSTOMATA
Amniota
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
Amniota: amniotic egg
f. Class REPTILIA
some distinguishing characters:-scales: keratin-Ectothermic (“cold-blooded”): relies on environment for heat source-3 chambered heart
diversity:-ca. 6500 species
ORDERSi. Testudines – turtlesii. Sphenodontia – tuatarasiii. Squamata – lizards and snakesiv. Crocodilia – crocodiles and alligators
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
g. Class MAMMALIA
some distinguishing characters:-presence of mammary glands: milk production for young-hair from keratin-four chambered heart-endothermic (“warm blooded’): can generate heat internally-internal fertilization, embryo develops in uterus
diversity:-ca 4500 species(most radiation occurred after dinosaur extinction (Cretaceous ca 70 mya))
I. CHORDATA
C. Subphylum: Vertebrata –vertebrates
2. Superclass GNATHOSTOMATA
g. Class MAMMALIA
where did mammals come from?
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
g. Class MAMMALIA
2 major groups: Monotremes and Therian (Marsupial + Eutheria)
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
g. Class MAMMALIA
Monotremes: echidna, platypus
characters:-lay eggs-produce milk but lack nipples
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
g. Class MAMMALIA
Marsupials: opposums, kangaroos, koalas
characters:-young are born at a very underdeveloped stage, and grow in mother’s pouch
(marsupium)http://www.sciencenmore.com/koala.jpg
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I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
g. Class MAMMALIA
Eutherians: most familiar mammals (outside Australia)
characters:-long period of pregnancy so young is born more developed than marsupials-well developed placenta, which connects young to mother in the uterus
Marsupials currently dominate Australia
Eutherians dominate the rest of the world
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
2. Superclass GNATHOSTOMATA
h. Class AVES: birds
Some distinguishing characters:-endothermic-feathers-reduction of organs (for flight) like only one ovary, no teeth (bill)-special organs like gizzard-no true tail
diversity:8600 across 28 orders
RECONSTRUCTING THE EVOLUTION OF BIODIVERSITY
Evolution of Birds: Feathered Reptiles
SIMILARITIES BETWEEN EXTANT REPTILES AND BIRDS
-single point of attachment of skull to vertebral column:
occipital condyle (vs. 2 for mammals)
-single middle ear bone: stapes
(vs. 3-malleus, incus and stapes in mammals)
-multiple bones form the lower jaw
(vs. single fused mandible in mammals)
-Sex determination: females are heterogametic (ZW)
(vs. males are heterogametic in mammals: XY)
RECONSTRUCTING THE EVOLUTION OF BIODIVERSITY
Evolution of Birds: The missing link found -- Archaeopteryx
DINOSAUR-LIKE BIRD-LIKE
Teeth Wings with feathers
Bone Structure Furcula
No keel Reduce fingers
Small sternum
“True” tail
Gastralia
Info on fossil
RECONSTRUCTING THE EVOLUTION OF BIODIVERSITY
Evolution of Birds
FOSSILIZED FEATHERS FOUND IN Dromaeosaur a theropod dinosaur
www.nature.com
RECONSTRUCTING THE EVOLUTION OF BIODIVERSITY
Evolution of Birds www.nature.com
DISCOVERY OF NEW FOSSIL: Microraptor gui
RECONSTRUCTING THE EVOLUTION OF BIODIVERSITY
Evolution of Birds
Sinornis santensis {Cretaceous, ca. 140 mya)
CHARACTERS
- teeth
- strengthened hand, pectoral girdle and forearm (advanced flight)
- raising wing over body for flight
- large pygostyle (for tail control)
- perching feet (opposable toes)
RECONSTRUCTING THE EVOLUTION OF BIODIVERSITY
Evolution of Birds:
AVES
THERAPODS
ORNITHISCHIANS
PTEROSAURS
CROCODILIAN
THECADONTSca. 250 mya
ca. 150 mya
ARCHOSAUR LINEAGE
OTHER REPTILES
I. CHORDATA
C. Subphylum: Vertebrata – vertebrates
PROBLEM WITH REPTILIA
A paraphyletic group
How would you make it monophyletic?
CLASSIFICATION OF THE CHORDATES Phylum CHORDATA
Subphylum UROCHORDATA (Tunicates) Subphylum CEPHALOCHORDATA (Lancelets) Subphylum VERTEBRATA (Vertebrates)
Superclass AGNATHA (Jawless vertebrates) Class Cephalaspidomorphi
Subclass *Ostracodermi (Ostracoderms) Subclass Cyclostomata (Lampreys)
Superclass GNATHOSTOMATA Class *PLACODERMI (Placoderms) Class CHONDRICHTHYES (Cartilage fishes)
Subclass Elasmobranchii (Sharks and Rays) Subclass Holocephali (Chimaeras)
Class SARCOPTERYGII (Fleshy-finned fishes) Subclass Dipnoi (Lungfishes) Subclass Coelacanthimorpha (Coelacanths)
Class ACTINOPTERYGII (Ray-finned fishes) Subclass Chondrostei (Bichirs, Sturgeons, Paddlefishes) Subclass Neopterygii
Class DIPNOI (lung fish)Class AMPHIBIA (Amphibians)
Subclass *Labyrinthodontia (LabyrinthodontsSubclass Lissamphibia (Anurans, Urodeles & Caecilians)
* extinct groups
FISH
CLASSIFICATION OF THE CHORDATES Phylum CHORDATA
Subphylum UROCHORDATA (Tunicates) Subphylum CEPHALOCHORDATA (Lancelets) Subphylum VERTEBRATA (Vertebrates)
Superclass AGNATHA (Jawless vertebrates) Class Cephalaspidomorphi
Subclass *Ostracodermi (Ostracoderms) Subclass Cyclostomata (Lampreys)
Superclass GNATHOSTOMATA (continued)Class REPTILIA (Reptiles)
Subclass Anapsida (*Cotylosaurs and turtles) Subclass *Synaptosauria (Plesiosaurs) Subclass *Ichthyopterygia (Ichthyosaurs) Subclass Archosauria (*Thecodonts, *Pterosaurs,
*Dinosaurs, Crocodilians) Subclass Lepidosauria (Snakes, and Lizards) Subclass *Synapsida (Pelycosaurs and Therapsids)
Class AVES (Birds) Subclass *Archaeornithes (Ancestral birds) Subclass Neornithes (True birds)
Class MAMMALIA (Mammals) Subclass Prototheria (Egg-laying mammals) Subclass Theria (Viviparous mammals)
Infraclass Metatheria (Marsupials) Infraclass Eutheria (Placentals)
* extinct groups
AMNIOTA