deuterostomes Flashcards
deuterostomes phylum
echinoderm
hemicordates
chordates
deuterostome properties
mouth derives from second opening
distinctionb etween deuterosomtes and protostomes
is becoming fuzzy;
prosostomes, ecdysozoa and lophotrochozoa all clearly a monophyletic group;
not all prostomes are spiral cleavers
not all prosostomes prosostomes
examples of non-protostomes protostomes
chaetognaths(lophotrophozoa) and priapulids (ecdysozoa)
develop secondary mouth
trimery
having 3 segments; usually a deuterostome feature
-could be a primtiive characteristics of triplomblasts lost in prostostomes
first triploblast
probably a deuterostosome as Braciopods develop similarliy but are prostomes due to de-volution
scientific confusion aboout lophophores
are the protostomes? (ribosomal dna evience) but have tri-partheid body of a deuterostome
annelids rigdea worm
is made up of three segments
previousally classifed deuterostomes
chateongraphs (now lophotrophozoa)
bracio pods
annelids
telophores
brachiopods
similar prostomes charteristics
chaetographs
are lophotrophozoa; ; had similar characteristics (trimery and radial cleavage) but were reclassified due to genome sequence
abulacrania
clade consisting of echinoderms and hemicordhates
echinoderm examples
star fish and sea urchin
hemichordate example
worms
chordate examples
vertebrates such as apes
popular belief about deuterostomes
that they started as sessil filter feeders (similar to echinoderms) and then developed into hemichordates as free swimming larvae and eventually complexified into vertebrates (not true tho)
truth about deuterstome-conception development
- echinoderms are the first despite being simple
- hemichordates arent a sistergroup of chordates, instead echinoderms and hemichorates more embryologically similar
- larvae comparisons shows echinodersm and hemichordates are closely related
echinoderms and hemichordates
- closeley related; molecular data shows similar larvae and embryological stages
- similar nervous systems
calcihodrate
stylophoria; disputed for long time but are an early echinoderm fossil
fould out by characteristics of echindoerm of mineralized skeleton that forms a spong like mesh; stereom catalatic endoskeleton similar to sea urchin skeleton
chordates and hemichordates
have mouths where water enteres and slips into gills
these pharangeal slits found in fossilied echindoerms
urochordates
used to be classified as molluscs but actually chordates due to embryologically similarities
are sessile filterfeers
eggs are tadpole larvae; fish like and have notochords
have dorsal nerve cord, pharyngeal slits, anus and post anal tai and are muscular segmented
cephalochordates
also have notocord and stiffening rod for rigid muscles and dorsal nerve cord
fishliked and usualyl filter feed
truth about urochordates, cephalochordates and vertebrates
urochodates more closely related to vertebrates than fish like cephalochordates
-ancestor of urochordates more complex but have lost charateristics from active predator to passive filter feeder
hence vertebrates + urochordates form a clade and cephalochordates are a sister group
inversion of dorsoventral axis
vertebrates have a dorsal nerve cord; invertabrates have a ventral nerve cord BECAUSE at one point in history vertebrates flipped over
