I. CHORDATA - San Francisco State Universityonline.sfsu.edu/jrblair/biol170/IntroVert1.pdf · 4....

I. CHORDATA

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

I. CHORDATA


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


-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



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


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



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



Three classes of bony fishes: “Osteichthyes”

distinguishing characters:-ossified skeleton-presence of swim bladder

I. CHORDATA



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



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



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


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



Acanthostega, a tetrapod fish

I. CHORDATA



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



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


I. CHORDATA



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



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


g. Class MAMMALIA

where did mammals come from?

I. CHORDATA



g. Class MAMMALIA

2 major groups: Monotremes and Therian (Marsupial + Eutheria)

I. CHORDATA



g. Class MAMMALIA

Monotremes: echidna, platypus

characters:-lay eggs-produce milk but lack nipples

I. CHORDATA



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



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


I. CHORDATA



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)


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


Evolution of Birds

FOSSILIZED FEATHERS FOUND IN Dromaeosaur a theropod dinosaur

www.nature.com


Evolution of Birds www.nature.com

DISCOVERY OF NEW FOSSIL: Microraptor gui


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)


Evolution of Birds:

AVES

THERAPODS

ORNITHISCHIANS

PTEROSAURS

CROCODILIAN

THECADONTSca. 250 mya

ca. 150 mya

ARCHOSAUR LINEAGE

OTHER REPTILES

I. CHORDATA


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

I. CHORDATA - San Francisco State Universityonline.sfsu.edu/jrblair/biol170/IntroVert1.pdf · 4....

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