Transcript Chordata

Chordata
I. Chordate Characteristics
A. Four characteristics must be present at
some time in life.
1. Notochord
- long flexible rod along dorsal side
- provides simple skeleton in invertebrates
- vertebrates retain only remnants
Chordate Characteristics cont’d
2. Dorsal hollow nerve cord – neural tube
- develops from plate of ectoderm
- dorsal to notochord
3. Pharyngeal gill slits
- embryonic slits by pharynx
- filter feeding device in invertebrates
- gas exchange in vert.
4. Muscular postanal tail
B. 3 Subphyla
1. Urochordates – tunicate – invertebrates
larval form has all 4 chordate traits
Subphyla cont’d
2. Cephalochordates – lancelet – invertebrates
segments formed from blocks of mesoderm
called somites (seen in many embryos)
Subphyla cont’d
3. Vertebrates
II. Vertebrate Characteristics
1.
2.
Highly cephalized – well developed brain
Formation of neural crest – band of cells
that pinch off neural tube and migrate
throughout body to help in formation of
other structures
Vertebrate Characteristics cont’d
3. Vertebral column
- skeletal unit that enclose nerve cord
- axial skeleton – cranium, vert. column,
ribs, sternum
- appendicular skeleton – supports two
pair of appendages
4. Closed circulatory system with ventral
heart
III. 2 Superclasses of Vertebrates
Superclass Agnatha – jawless fish
 Superclass Gnathostomata – divided into
Gnathostomata I and Gnathostomata II
- Gnathostomata I
Class Chondricthyes – cartilage fish
Class Osteicthyes – bony fish
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Superclasses cont’d
- Gnathostomata II – Tetrapods
- Amphibians – link to land & water
- Amniotes – Reptiles, Aves, Mammals
IV. Detailed Chordate Classes
A. Agnatha pg. 685
- no jaw, circular mouth w/teeth
- notochord persists for life
- 2 chambered heart (as in all fish)
- ectothermic (cold-blooded)
- lack paired appendages
- lampreys & hagfish
B. Chondricthyes
- cartilage fish
- sharks, rays, skates
- hinged jaw w/teeth, anterior & ventral
- notochord replaced by cartilage vertebrae
- gill slits present
Chondricthyes cont’d
- stays buoyant by oil in liver & continuous
swimming
- acute senses including lateral line (row of
organs sensitive to changes in water
pressure)
Chondricthyes cont’d
Internal fert. – male has claspers to transfer
sperm into female rep. tract
 3 ways young are developed
- oviparous: lay eggs that hatch outside
mothers body
- ovoviviparous: retain fert. egg in oviduct,
nourished by egg yolk then hatch in uterus
- viviparous: young develop in uterus &
nourished by a placenta
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C. Osteicthyes

Hinged jaw w/anterior mouth
Osteicthyes cont’d
Notochord replaced by calcium phosphate –
vertebrae
 Gills covered by operculum (protective
flap) allows fish to stand still

Osteicthyes cont’d
Swim bladder provides buoyancy
 Lateral line
 Skin glands secrete mucus

3 subclasses of Osteicthyes
1.
2.
3.
Ray-finned fish
Lobe finned fish
Lung fish
Ray-finned
Very maneuverable fins
 Perch, bass, most familiar fish
 Supported by flexible rays for defense &
movement

Lobe-finned
Rounded fin to prop up body
 Only one species left - Coelocanth
 Freshwater
 Lungs & gills
 Bottom dwellers – used pelvic & pectoral
fins to “walk”
 Gave rise to amphibians

Lungfish
No gills, only lungs
 Similar to lobe-finned
 3 kinds alive
 Live in stagnant ponds, swamps
 Come up and gulp air into lungs
 Burrow into mud in dry season (type of
hibernation)
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D. Amphibia
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Descended from lobe-finned fish 350 mil. yrs. ago
“2 lives” – refers to metamorphosis
egg  tadpole  adult
Most stay near water
External fert. with much variety in egg carrying
Many show complex & diverse social behavior
E. Reptiles
Scales w/keratin waterproof the skin
 Well developed lungs
 Ectothermic – behavioral adaptations help
control body temp.
 3 ½ chambered heart – beginning of septum

Reptiles cont’d
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Internal fert leads to development of
amniote egg pg. 693
- amnion – protection
- chorion – gas exchange and protection
- allantois – wastes, gas exchange
- yolk sac – food supply
Age of Reptiles
250-300 mil. yrs. ago
 Plants & insects already here for food
 Extinction of dinosaurs 65 mil. yrs. ago

Aves link to reptiles

Fossil of Archaeopteryx
- clawed forelimbs w/scales
- teeth
- long tail w/vertebrae
- feathers – endothermic?
- weak flyer – small sternum
- tree dwelling glider?
F. Aves
Birds
 Endothermic
 Amniote egg
 Scales of legs (keratin)
 4 chambered heart
 Layer of fat insulates some

Aves cont’d

Adaptations for flight
- wings & large sternum
- strong pectoral muscles
- feathers (keratin laced)
- toothless
- one ovary
- honey-combed bones
- lungs & air sacs
G. Mammalia
Mammary glands
 Hair laced with keratin
 Endothermic
 4 chambered heart
 Diaphragm
 Most bear live young – viviparous

3 Subclasses
1. Monotremes – egg laying
- eggs hatch hours after they’re laid
- no nipples – milk secreted from glands,
young sucks milk from fur
- duck-billed platypus, spiny anteater
3 Subclasses cont’d
2. Marsupials – pouched mammals
- young climb into pouch after birth to
finish development
- kangaroo, oppossum
3 Subclasses cont’d
3. Placental mammals
- bear live young that have been nourished
by a placenta
- most mammals