Prodochordates and Chordate Characters Flashcards
what are chrodates?
bilaterally symmetrical deuterostomes
Protostomes (“first mouth”)
spiral (offset cleavage), coelom develops from the splitting of the mesoderm (schizocoelom), blastopore forms mouth
Deuterostomes (“second mouth”)
radial (aligned) cleavage, coelom develops of outpouching of gut (enterocoelom), blastopore forms the anus
How many sub-phylums does Phylum Chordata have? what are they?
3 subphyla: cephalochordata, vertebrata, urochordata
what are the six chordate synapomorphies?
notochord, dorsal hollow nerve cord, pharyngeal slits, myomeres, postanal tail, endostyle
notochord
hydrostatic organ with elastic properties that resist axial compression. Largely replaced by the vertebral column in vertebrates. nucleus pulposus in mammals.
dorsal hollow nerve cord
induced by the notochord the notochord, develops into the nervous system in vertebrates through neurulation. In non-chordates it is ventrally placed and solid
pharyngeal slits
series of small openings that pierce the pharynx.
postanal tail
posterior extension of the body past the anus used for locomotion, defense, counter-balance etc.
endostyle
involved in mucus production and/or iodine metabolism
myomeres
muscle blocks involved in locomotion
what function do pharyngeal slits serve in protochordates?
food suspended in water enters the pharynx, food gets trapped in mucus, water exits through the pharyngeal slits
what function do pharyngeal slits serve in vertebrates?
the pharynx develops a series of pouches (in place of slits) during embryonic growth. this is an exaptation for respiratory exchange (walls of the pouches become vascularized for gas exchange)
Where is the endostyle found in protochordates?
on the pharyngeal floor that produces mucus to trap food and synthesizes iodine binding proteins
what is the endostyle homologous with in vertebrates?
the subpharyngeal gland and thyroid gland (synthesizes iodine binding proteins)
Protochordates
informal group consisting of hemichordates, cephalochordates, and urochordates, have 1 or more chordate character at some point in devrlopment
what type of feeders are protochordates?
passive suspension feeders, using cilia and mucus
Hemichordates (acorn worms)
posess pharyngeal slits (not a chordate) that is used to get rid of excess water, uses a ciliated proboscis for locomotion and feeding
How many chordate characters do cephalochordates posses?
all 6
what function does the ciliated wheel organ serve in branchiostoma?
the ciliated wheel organ draws in water and food particles (then sorted by buccal cirri and velum)
what function does hatschek’s pit serve in branchiostoma?
mucus secretion and possible endocrine function
What is the oldest known cephalochordate?
Pikaia gracilens (508 MYA)
How many chordate characters do ascidian larvae have?
5, 6 including weak myomeres
How many chordate characters do adult urochordates have?
2
what are adhesive papillae used for?
they are used by ascidian larvae to attach to suitable substrate
What is the function of the statocyst?
to sense gravity
what is the function of the ocellus?
to sense light
what is the auricularian hypothesis of chordate evolution?
started with echinoderm larvae, multiple occurrences of paedomorphosis eventually evolved chordates
how many sets of genes specify the dorsoventral axis of the body?
2 sets, code for proteins with a prominent role in dorsal-ventral patterning
In echinoderms and Hemichordates, which protein determines the dorsal surface?
BMP (bone morphogenetic protein)
In echinoderms and hemichordates, which proteins determine the ventral surface?
chordin
