CH 25: ANIMAL DIVERSITY II: VERTEBRATES
What are the key features of chordates?
All chordates have deutorestome development (mesoderm pockets pinch off of the
digestive cavity to form coelom) and four distinctive structures at some stage of
development.
Bilateral
Cephalization
3 embryonic germ layers
Endoderm:
o produce inner germ layer lining the gut
o differentiates to form tissues lining respiratory surfaces,
the gut, hollow organs
Ectoderm:
o produce outer layer covering outside the body
o Forms nerve tissue and tissues on outer surface of body
Mesoderm:
o lies between the endoderm and ectoderm
o Forms muscle, circulatory and skeletal systems
Four structures of chordates:
Dorsal nerve chord
o Lies above the digestive track, running lengthwise along upper body
o Hollow
o The center filled with fluid
o Develops during embryonic development
o Thickened anterior end becomes brain
Notochord (skeleton comes from notochord)
o Stiff rod extending along the length of the body between the digestive track and
nerve cord
o Body support
o Attachment site for muscles
o Present during early embryonic stages of development and disappears as
skeleton develops
Pharyngeal gill slits
o Located in the pharynx
o Slits may form gills or grooves during early stages of development
Post-anal tail
o Extension of posterior end extending past anus
o Contains muscles and rearmost portion of nerve cord
, o Some species lost tails during development
Humans = chordates (Taxonomic group) deuterostome development
Evolutionary relations are seen most clearly in early stages of development
During embryonic phase we develop and lose our notochord, gill slits & tail
What animals are chordates?
Chordates include 3 clade (groups including descendants of a common ancestor)
o Tunicates
Marine invertebrate chordates
Hermaphroditic reproducing sexually or asexually by budding
Small (mm – 1 ft)
Immobile/ filter-feeding, vased-shaped animals seasquirts
Majority of body occupied by pharynx (backset perforated by gill slits,
lined with mucus)
Incurrent siphon: water enters
Mucus: traps food particles which move to digestive track
Excurrent siphon: water exits body
Adults sessile, larvae swim possessing 4 chordate features
Lancelets (cephalochordate)
Small (2 in – 5 cm)
Invertebrates
Fishlike animals containing chordata features as adult
Cilia in pharynx draws seawater into mouth and out through gills
Mucus filters food particles and is transported to digestive tract
Separate sexes and reproduce sexually
Craniates
Share same ancestor as lancelets and tunicates
All chordatas with a skull enclosed brain made of bone, cartilage or tissue
resembling bone
Craniates are vertebrates
What are the key features of chordates?
All chordates have deutorestome development (mesoderm pockets pinch off of the
digestive cavity to form coelom) and four distinctive structures at some stage of
development.
Bilateral
Cephalization
3 embryonic germ layers
Endoderm:
o produce inner germ layer lining the gut
o differentiates to form tissues lining respiratory surfaces,
the gut, hollow organs
Ectoderm:
o produce outer layer covering outside the body
o Forms nerve tissue and tissues on outer surface of body
Mesoderm:
o lies between the endoderm and ectoderm
o Forms muscle, circulatory and skeletal systems
Four structures of chordates:
Dorsal nerve chord
o Lies above the digestive track, running lengthwise along upper body
o Hollow
o The center filled with fluid
o Develops during embryonic development
o Thickened anterior end becomes brain
Notochord (skeleton comes from notochord)
o Stiff rod extending along the length of the body between the digestive track and
nerve cord
o Body support
o Attachment site for muscles
o Present during early embryonic stages of development and disappears as
skeleton develops
Pharyngeal gill slits
o Located in the pharynx
o Slits may form gills or grooves during early stages of development
Post-anal tail
o Extension of posterior end extending past anus
o Contains muscles and rearmost portion of nerve cord
, o Some species lost tails during development
Humans = chordates (Taxonomic group) deuterostome development
Evolutionary relations are seen most clearly in early stages of development
During embryonic phase we develop and lose our notochord, gill slits & tail
What animals are chordates?
Chordates include 3 clade (groups including descendants of a common ancestor)
o Tunicates
Marine invertebrate chordates
Hermaphroditic reproducing sexually or asexually by budding
Small (mm – 1 ft)
Immobile/ filter-feeding, vased-shaped animals seasquirts
Majority of body occupied by pharynx (backset perforated by gill slits,
lined with mucus)
Incurrent siphon: water enters
Mucus: traps food particles which move to digestive track
Excurrent siphon: water exits body
Adults sessile, larvae swim possessing 4 chordate features
Lancelets (cephalochordate)
Small (2 in – 5 cm)
Invertebrates
Fishlike animals containing chordata features as adult
Cilia in pharynx draws seawater into mouth and out through gills
Mucus filters food particles and is transported to digestive tract
Separate sexes and reproduce sexually
Craniates
Share same ancestor as lancelets and tunicates
All chordatas with a skull enclosed brain made of bone, cartilage or tissue
resembling bone
Craniates are vertebrates
