1: The deuterostomes: Chordates

Question 1

What phylums make up the chordates?

Answer 1

Urochordates (tunicates)
Cephalochordates
Vertebrates

Question 2

What are the 4 key characteristics of the Chordates

Answer 2

Notochord (stiffening rod that runs through the animal)
Dorsal, hollow nerve cord
Pharyngeal (gill) slits
Post-anal tail (tail goes beyond the anus)

Question 3

Describe the Urochordates metamorphosis

Answer 3

(tunicates)
- Larvae have all chordate features
- During metamorphosis all chordate features significantly reduce apart from pharyngeal slits → used for filter feeding
Reorganisation:
- Notochord loses turgor
- Tail absorbed
- Rapid growth between buccal siphon & papillae = twists animal round

Question 4

Most tunicates are ___ ______

Answer 4

Sea squirts

Question 5

Compare the nervous system of Echinoderms, Hemichordates and Chordates

Answer 5

Echinoderms: Nerve ‘net’/ring
Hemichordates: Nerve ‘net’ though can be hollow
Chordates: Dorsal hollow nerve cord

Question 6

Compare the Phyarygeal gill slits in the Echinoderms, Hemichordates and Chordates

Answer 6

Echinoderms: Only present in fossil homalozoans
Hemichordates: Present and used for respiration
Chordates: Present

Question 7

Compare the prescence of a notochord post anal tail in Echinoderms, Hemichordates and Chordates

Answer 7

Echinoderms: Absent
Hemichordates: Absent
Chordates: Present

Question 8

What is the main difference between deuterostomes and chordates?

Answer 8

dorsoventral axis inversion is present in chordates
- Chordates are flipped upside down: nerve cord if dorsal