Topic 17

Question 1

What are the three synapomorphic characteristics of phylum echinodermata?

Answer 1

1. Radial symmetry in adults
2. Calcareous endoskeleton (contains calcium carbonate)
3. Water vascular system

Question 2

What are the basic characteristics of the phylum echinodermata?

Answer 2

slow, sessile, marine

adults: pentaradial symmetry

larvae-bilateral symmetrical

mouth at center of arms and faces down

thin epidermis covers endoskeleton

tube feet: locomotion, feeding, detection and gas exchange

Question 3

What is the class asteroidea?

Answer 3

sea stars

5 arms (or more)

active, walk via tube feet

predatory

use tube feet to pry open bivalves

adhesion due to glue, not suction

Question 4

What is the class echinoidea?

Answer 4

sea urchins, sand dollars

no arms

5 rows of tube feet

slow moving

spines: locomotion and protection

eat seaweed

Question 5

What is the class holothuroidea?

Answer 5

sea cucumbers

elongated: symmetry is secondarily bilateral, 5 rows of tube feet, some tube feet around the mouth serves as feeding tentacles

deposit or suspension feeders

shoot out internal organs if disturbed

Question 6

What are the four synapomorphies of the phylum chordata?

Answer 6

1. Notochord: cartilaginous skeletal structure, flexible rod located dorsally between the digestive tube and the nerve cord, stiff but not rigid support along body, present in all chordate embryos and some adults
2. Dorsal, hollow nerve chord: unique to chordates, develops from neural plate of ectoderm, plate rolls into tube during embryonic development, nerve cord –> spinal cord and brain
3. Pharyngeal clefts: located just posterior to mouth along digestive track
4. Muscular, post-anal tail: most adult chordates have muscular tail posterior to anus, contains muscles and skeletal elements, reduced in many species during embryonic development

Question 7

What are the seven vertebrate derived character states?

Answer 7

1. Two or more clusters of Hox genes
2. Neural crest
3. Endoskeleton and pronounced cephalization
4. Circulatory system modified
5. Pharyngeal clefts
6. Vertebral column (backbone)
7. Elaborate skull (cranium)

Question 8

What are the key concepts of chordates?

Answer 8

deuterostomes are a monophyletic group

echinodermata body plan (radial symmetry in adults, endoskeleton, and water vascular system)

ancestral chordate body plan has been retained but modified in diverse lineages
vertebrate evolution shows development of brain, and diversification of feeding methods
duplication of Hox genes led to development of complex body structures