deuterostomes- chordates Flashcards
deuterostomia are part of the
bilateria
2 phyla of deuterostomia
echinoddermata and chordata
what constitutes a deterostome
- bilateral symmetry
- coelom (body cavity)
- radial cleavage during embryonic development ; cleavage parallel to vertical axis
- blastopore –> anus
echinodermata
(deuterosomes)
starfish, sand dollars, sea urchins, sea lilies, sea cucumbers and brittle stars
DNA data indicates that echinoderms are closely related to
chordates
echinodermata endoskeleton
- interlocking CaCO3 (calcareous) plates and spines
- covered by a thin epithelium
echindermata water vascular system
- unique, network of water-filled canals
- branch to form tube feed
- locomotion and feeding
echinodermata sexual reproduction
release gametes into water, spawning
also asexual; autotomy; ie lose an arm “comet” becomes new individual
5 classes of echindoermata
1) asteroidea: starfish and sea daisies
2) echinoidea: sea urchins
3) ophiuroidea; brittle stars
4) crinoidea; sea lillies and feather stars
5) holothuroidea; sea cucumbers
3 subphyla of chordata
- vertebrata; fish, amphibians, reptiles, bird, mammals
- cephalochordata;amphioxus
- urochordata; sea squirts
when did earliest chordate appear
cambrian period 530 MYA
4 common feature
- notochord
- pharyngeal slits
- dorsal, hollow nerve cord
- muscular, post-anal tail
the 4 common features that define chordates; when are they exhibited
may only be present briefly during embryonic development of may persist into adulthood, but all chordata exhibit them at some point
notochord
chordata criteria #1
- slender rod
- develops from mesoderm
- lies dorsal to coelom (body cavity)
- beneath and parallel to CNS (under the brain and hollow nerve cord)
- consists of a core of cells and fluid, surrounded by fibrous sheath
how does notochord allow locomotion
through lateral undulations
in bony fish and terrestrial vertebrates when is notochord present and what is it replaced by
- embryonic development
- replaced by vertebral column
- persists as nucleus pulposus of the intervertebral discs
pharyngeal slits
chordata criteria #2
- longitudinal series of openings in walls of pharynx
pharyngeal slits in primitive chordates
involved in feeding
pharyngeal slits in terrestrial vertebrates
in embryo phase and lost during embryogenesis
pharyngeal slits in aquatic vertebrates
gills develop ADJACENT to pharyngeal slits, slits allow for flow of water across gills
dorsal hollow nerve cord
chordata criteria #3
- derived from ectoderm
- lies above hut
- hollow
- surrounds fluid- filled neurocoel
muscular, post anal tail
chordata criteria #4
- posterior elongation of body beyond anus
- consists of segmental musculature and the notochord
what resembles the earliest chordate, what is a living example
- cephalochordata
- living example is branchiostoma; amphioxus
branchiostoma; amphioxus
- subphylum cephalocordata
- blade like in shape
- all 4 criteria of chordate as an adult
- filter feed, mucous nets across slits
cephalochordata digestive system
- may be precursor of vertebrate organs
- midgut caecum; liver and pancreas
cephalochordata circulatory system
- same general pattern as vertebrates
- ventral and dorsal aorta
- afferent and efferent vessels
- capillary networks
- NO HEART
cephalochordate brain
- shares homology w vertebrate brain
- not a rela brain; cluster of cells
- expression of genes; similar organization of forebrain, midbrain and hindbrain
vertebrate brain is an elaboration of the
cephalochordate brain
urochordata
- tunicates
- all species marines
- class ascidiacea; sea squirts
sea squirts
- in urochordata phylum
- class ascidiacea
- adults sessile, larva planktonic
- display 4 criteria of chordates only as larva
likely that urochordates and vertebrates
evolved from a common ancestor
urochordata (sea squirt) CNS 3 divisions
sensory vesicle, visceral ganglion and nerve cord
urochordata (sea squirt) neurel crest cells
- derived from nerve cord
- different cell types
urochordata (sea squirt) heart and blood
- rudimentary blood
- several blood types of cells
from the chordates evolved the craniates which are
chordates with a head
craniata unique characteristic
is the neural crest
most basal of crianates
hag fish
hag fish
- most basal craniate
- cartilaginous skull
- lacks jaw and vertebrae
- retain notochord in adult
- marine
- feed on detritus
- produce mucous as defense
during cambrian period craniates gave rise to
vertebrates
most basal lineage of vertebrates are
lampreys
lampreys
- most basal vertebrates
- weird looking fish with big circle mouth/ teeth
- cartilaginous skeleton
- lack jaw
- retains notochord in adult
- marine and freshwater
one of most significant steps in early vertebrate evolution
development of jaws in primitive fish
gnathostomes
- vertebrate fish w jaws
- transition from suspension feeding to selective feeding
- paired pectoral and pelvic fins
- 2 lines of evolution:
- chondrichthyes; cartilaginous fish
- oteichthyes; bony fish
chondrichthyes
gnathostomes
vertebrates
chordates
- sharks, rays and relatives
- cartilaginous skeleton
- cartilaginous vertebral column replaces notochord
- lack swim bladder
- placoid scales; dentine and enamel with surface denticles
- scales project through epidermis
- internal fertilizations
- males have clasper on pelvic fine
- oviparous; tough leathery eggs
- AND viviparous; gestation, nutrition via yolk, uterine milk or placenta
osteichthyes
gnathostomes
vertebrates
chordates
- bony fish
- scales do not penetrate epidermis
- swim bladder controls buoyancy
- external fertilizations
2 subclasses of osteichthyes
gnathostomes
vertebrates
chordates
- actinopterygii; ray finned fish
- sarcopterygii; lobe- finned fish
actinopterygii; ray finned fish
2 main groups
bony fish ie osteichthyes
- neopterygii: teleosts
- palaeonisciformes; sturgeons
sturgeons
- largest species of freshwater fish
- toothless
- vertebrata
- have a jaw so gnathostomes
- bony fish so osteichthyes
- ray finned so actinopterygii
- sarcopterygii; lobe- finned fish
bony fish
- lung fish and coelacanth
- flesh fins composed of soft muscle
- gave rise to tetrapod limb!
where did limbs arise from
lobe finned fish ie subclass sarcopterygii of bony fish
osteichthyes
gnathostomes
vertebrates
chordates
subclass sarcopterygii
cam breath air when O2 levels in water fall
prominent notochord
cool ex of sarcopterygii
coelacanth
thought ot be extinct but found in 1938
tiny vertebrate
possess swim bladder
