Lesson 3 - Protochordates and the Origin of Craniates Flashcards
what is present in protochordates
- bilateral symmetry
- pharyngeal slits
- notochord
- dorsal hollow CNS
- postanal tail
- endostyle
- had bony plates and scales (armored fishes)
- jawless vertebrates
- small bony scales fitted tightly where there are no scales
ostracoderms
when did ostracoderms occur
late Cambrian period through the Devonian
(400-525 million years ago)
primitive fish that have many similarities to living hagfish and are the oldest vertebrates (530 my) ever found
- Myllokunmingia fengjiaoa
- Haikouichthys ercaicunensis
when did Myllokunmingia fengjiaoa
and Haikouichthys ercaicunensis live
530 million years ago
- literally the ‘Chinese eel of good fortune’
- earliest known chrodate
- thought to be a fossil relative of modern lancelets
Cathaymyrus diadexus
proposed the establishment of Phylum Chordata in 1874
Ernst Haeckel
Subphylums under Phylum Chordata
- Urochordata
- Cephalochordata
- Craniata
subset of the larger group of animalia and share common features in development
basal deuterostomes
- presence of calcium carbonate skeleton
- presence of a secondary radial symmetry except in the most basal members
- Cambrian to present
Echinoderms
example of echinoderms
- starfish
- sea urchins
- sea cucumbers
- sea daisies
- crinoids
- acorn worms
- marine organisms that live in the mud under shallow waters
- fragile when handled
- 1.5 meters
- with invertabrate and chordate features
Hemichordates
added Hemichordates (acorn worms) to the Phylum Chordata
Bateson
why did Bateson add acorn worms to the Phylum Chordata in 1884
- dorsal, hollow nervous system
- gill slits
- short diverticulum of the gut (stomochord)
- short diverticulum of the gut
- not homologous with notochord
stomochord
- marine chordates
- notochord is confined to the locomotor tail of the free-living larval stage and lost during metamorphosis into sessile adults
- enclosed within a delicate, nonliving, and colored transparent tunic
- filter feeders
- posses pharyngeal slits
Urochordata
urochordata are enclosed within a delicate, nonliving, and colored transparent __
tunic
- sea squirts
- solitary or colonial populations
- larvae, have fleeting existence and do not feed (subsist on nutrients stored in the tissues)
Ascidians
three unequal regions of Hemichordates
- proboscis
- collar
- trunk
parts of the Ascidian larva
- mouth
- pharyngeal slit
- atriopore
- external opening through which water exits the body after passing through the pharyngeal slits
- plays a key role in their filter-feeding system and respiratory process
atriopore
Features of the Subphylum Cephalochordata
- notochord
- dorsal, hollow nervous system
- pharyngeal gill slits
- ‘circulatory’ system - vertebrate pattern with pumping vessels but no heart
where is the locomotor musculature of subphylum cephalochordata found
muscles segments lie just under the skin
subphylum cephalochordata :
__ extend the entire length of the organism (locomotor muscle)
myomeres
skin of subphylum cephalochordata
single layer of epidermis
respiration of subphylum cephalochordata
cutaneous respiration