Lecture 15- Agnatha

Question 1

What are the 3 subphyla of the phylum Chordata

Answer 1

1. Urochordata (tunicates) NV
2. Cephalochordata (lancelets) NV
3. Vertebrata

Question 2

Name these Chordate features

Answer 2

Question 3

How do Tunicates have chordate features

Answer 3

• There sessile invertebrates
• They filter feed
• Have active swimming larvae
• Their larvae have all vertebrate features

Question 4

Whats Garstangs 1928 hypothesis on Urochordates as ancestors

Answer 4

The evolution of vertebrates from a urochordate

Question 5

Label Garstangs hypothesis

Answer 5

Question 6

What’s Neoteny/Paedomorphisis and an example

Answer 6

• Where juveniles/larval traits in adult body
• May attain sexual maturity in juvenile from (progenesis)
  EG. Axolotl

Question 7

What species ha a sessile adult with no chordate features

Answer 7

Ascidian

Question 8

When was larva discovered and describe Urochordate larva

Answer 8

1869
Free swimming with all chordate features

Question 9

What are free-living urochordates called

Answer 9

Larvaceans

Question 10

How features do vertebraes share with chordates (4)

Answer 10

• dorsal hollow nerve cord
• notochord
• pharyngeal gill slits
• post anal tail

Question 11

What are the 2 classes of Agnatha and some characteristics

Answer 11

1. Hagfish (Myxini)
2. Lampreys (Petramyzontida)
   - manintans notochord throughout life
   - has cranium but no jaw