Post on 21-Jan-2016
Lecture #14
Phylum Chordata: The vertebrate Phylum
Phylum Chordata
• only 45,000 species• characteristics:– 1. bilaterally symmetrical– 2. notochord– 3. pharyngeal gill slits– 4. dorsal, hollow nerve cord– 5. post-anal tail– 6. complete digestive system– 7. thyroid gland– 8. ventral, contractile heart
Numbers 1 – 5 may be ina unique combination andare found at some stage in development
• Chordate classification characteristics:
• Notochord? No Echinoderms• Notochord? Yes keep evolving• Brain? No Urochordate
(tunicate)• Brain? Yes keep evolving• Head/Cranial cavity? No
Cephalochordate (lancelet)• Cranial cavity? Yes keep
evolving• Vertebral column? No Hagfish• Vertebral column? Yes
Lampreys & keep evolving baby!!!
Chordates
E ch i
n ode
r mat
a(s
iste
r gr o
up t o
ch o
rda t
e s)
Craniates
Vertebral column
Head
Brain
Notochord
Ancestral deuterostome
C ep h
a lo c
h ord
ata
(l an c
elet
s)M
y xi n
i(h
a gfi s
hes )
C ep h
a la s
p id o
mor
p hi
(l am
prey
s )
Uro
c ho r
data
(tu n
i ca t
e s)
Phylum Chordata
• notochord:– supportive rod that extends most of the animal’s
length – extends into the tail – dorsal to the body cavity– flexible to allow for bending but resists
compression– composed of large, fluid-filled cells encased in a
fairly stiff fibrous tissue– will become the vertebral column in many
chordates
Phylum Chordata
• dorsal, hollow nerve cord:– runs along the length of the body – dorsal to the
notochord– expands anteriorly as the brain– develops from ectoderm– BUT: in most vertebrates – nerve cord is solid and
is ventral to the vertebral column
Phylum Chordata
• pharyngeal gill slits:– series of openings in the pharyngeal region of the
embryo– develop as a series of pouches separated by
grooves– in some embryos – grooves develop into slits– used in primitive chordates for filter feeding– in aquatic vertebrates – transformed these
slits/pouches into gills– embryonic in terrestrial chordates
Phylum Chordata
• SubPhyla:– Urochodata: sea squirts (tunicates)• notochord, pharyngeal gill slits, and tail present in free-
swimming larvae
– Cephalochordata: amphioxus• all four chordate traits persist through life
– Hyperotreti: hagfishes• jawless, no paired appendages
– Vertebrata: vertebrates
Subphylum Cephalochordata
• known as the lancelets• earliest diverging group of chordates• get their name (Lancelet) from their blade-like shape• embryos develop: a notochord, a dorsal, hollow nerve
cord, pharyngeal gill slits and a post-anal tail• filter-feeders – cilia draw water into the mouth• swim like fishes – chevron shaped muscles on either side
of the notochord
Pharyngealslits or clefts
Mouth
Brain
Dorsal,hollow
nerve cordNotochordMusclesegments
Muscular,post-anal tail
Anus
Subphylum Urochordata
• tunicates• embryonic/larval stage has the
characteristics of the chordate• larva swims to a new substrate
and undergoes metamorphosis – to form the adult tunicate
• retain the pharyngeal gill slits in the adults
• water flows in through an incurrent siphon - filtered by a net of mucus on the pharyngeal gill slits
Incurrentsiphonto mouth
Excurrentsiphon
Pharynxwith
numerousslits
Atrium
Tunic
Excurrentsiphon
AnusIntestine
EsophagusStomach
Craniates• chordates with a head• head – consists of a brain, surrounded by a
skull, and other sensory organs• living craniates all share a series of unique
characteristics• most basic craniate – hagfish
https://www.youtube.com/watch?v=t5PGZRxhAyU
Vertebrates
• branching off from the primitive chordates involved innovations in the nervous system and skeleton– vertebraes have a more extensive skull– development of the vertebral column composed of vertebrae
• most vertebrates – vertebrae enclose a spinal cord (replaces the notochord)
– development of fin rays in aquatic vertebrates– development of limbs in terrestrial vertebrates
• adaptations in respiration and circulation– more efficient gas exchange system – gills are modified in aquatic
vertebrates; lungs in the terrestrial vertebrates– more efficient heart – 2 to 4 chambered
• adaptations in thermal regulation– warm blooded vs. cold blooded
• adaptations in reproduction– amniotic egg– placental animals
Vertebrate Taxonomy
• most basal vertebrate – lamprey– jawless
• development of jaws marked the evolution of the gnathostomes
• development of ray-finned fishes• development of lobed fins marked
the evolution of lobe-finned fishes• development of limbs marked the
development of amphibians and reptiles
• development of mammary glands marked the development of mammals
lungs marked the evolution
• Vertebrate classification requirements:
• Vertebral column? No Hagfish
• Jaws? No Lampreys• Bony skeleton? No Sharks,
Rays• Lobed fins? No? Ray finned
fish• Lung derivatives? No
Coelocanth• Legs? No Lungfish• Amniotic egg? No Amphibian• Milk? No Reptile• What’s left??? MAMMALS!!
ChordatesE c
h in o
der m
ata
(sis
ter g
r oup
t o c
h ord
a te s
)
CraniatesVertebrates
GnathostomesOsteichthyans
Lobe-finsTetrapods
Amniotes
Milk
Legs
Amniotic egg
Mineralized skeleton
Jaws
Vertebral column
Head
Brain
Notochord
Ancestral deuterostome
C ep h
a lo c
h ord
ata
(l an c
elet
s)M
y xi n
i(h
a gfi s
hes )
C ep h
a la s
p id o
mor
p hi
(l am
prey
s )C h
o nd r
ich t
h yes
(sh a
r ks ,
rays
, ch i
ma e
ras)
Acti
n opt
ery g
i i(r
a y- fi
n ned
fis h
e s)
Acti
n is ti
a(c
o el a
c ant
h us )
Dip
n oi
(l un g
fi sh e
s)
Uro
c ho r
data
(tu n
i ca t
e s)
Am
p hi b
i a(f
rog s
, sa l
a ma n
der s
)R e
p tili a
(tu r
t les,
sn a
kes ,
c ro c
o dile
s , b
ir ds)
Ma m
ma l
ia(m
amm
a ls )
Lobed fins
Lung derivatives