Invertebrate Chordates Lecture 12

Question 1

what groups make up invertebrate chordates? (2)

Answer 1

Urochordata (tunicates) and Cephalochordata

- important to study to find out origin of vertebrates

Question 2

Notochord

Answer 2

Homologous to vertebrate spine
flexible, rod-shaped, defines primitive axis of embryo (derived of mesoderm)
always at some developmental stage
endoskeletal element
axis for muscle attachment

Question 3

Pharyngeal pouches and gill slits

Answer 3

formed by inpocketing of ectoderm, and evagination of endoderm of the pharynx
filter feeding apparatus or area of respiration in fishes
(lead to evolution of gills)

Question 4

Urochordates

Answer 4

Sea quirts (sessile) and Salps (pelagic)
free-swimming larvae with all chordate characteristics 
(notochord, dorsal nerve chord, pharyngeal gill slits and post-anal tail) which may be lost in the adult forms

Question 5

classes of Urochodata (3)

Answer 5

Ascidiacea (sessile, solitary or colonial)
Thaliacea (free-swimming, planktonic, often colonial)
Appendicularia (Larvacea)- free-swimming, resemble tadpole larvae

Question 6

Ascidiaceans

Answer 6

Sea quirts
filter feeders
adult lack most chordate characters, but possess pharynx with many gill slits and complex tunic (sessile)
Larvae possess all chordate characters

Question 7

body forms of Ascidiaceans (3)

Answer 7

Colonial (single test)
Solitary (Single test)
Compound (shared test and excurrent siphon)

Question 8

Thaliacea

Answer 8

Free-swimming, colonial or solitary
feed using mucous net
water current for locomotion and gas exchange

Question 9

Appendicularia

Answer 9

Pelagic, free-swimming
only tunicates to show all chordate features in adults
suspension feed with mucous house

Question 10

Sub-phylum Cephalochordata

Answer 10

Amphioxus (lancelets)
marine, benthic-like fish
burrow in mud
filter particles in mouth from seawater

Question 11

Chordate characters

Answer 11

Post-anal tail
Notochord
pharyngeal gill slits
Endostyle 
Dorsal nerve cord