Lecture 20

Question 1

Deuterostomia characteristics

Answer 1

1. bilateral symmetry
2. triploblastic
3. radial, indeterminate cleavage
4. enterocoelous coelom
5. blastopore does not become mouth

Question 2

Deuterostomia 2 phyla

Answer 2

1. Echinodermata (7000)

2. Chordata

Question 3

Phylum Echinodermata

Answer 3

sea stars, sea urchins, sea lilies, sea cucumbers, all aquatic

Question 4

echinodermata morphology

Answer 4

1. thin epidermis covers endoskeleton made of many ossicles
2. pentaradial symmetry (larvae bilaterally symmetrical) possibly evolved with Hox genes
3. oral and aboral sides
4. unique water vascular system
5. tube feet for locomotion, feeding, gas exchange
6. diffuse nervous system with no brain

Question 5

ossicles

Answer 5

small calcareous plates, can be close or widely distributed, give prickly texture

Question 6

water vascular system

Answer 6

network of hydraulic canals branching into extensions called tube feet, connects to sea water via special porous ossicle called the madreporite, fluid in the canals is sea water plus extra potassium, and some proteins plus free-roaming cells

Question 7

echinodermata reproduction

Answer 7

1. usually separate sexes

2. most engage in broadcast spawning (but larvae are brooded if internal fertilization)

Question 8

broadcast spawning

Answer 8

fertilization occurs in open water, larva is planktonic

Question 9

3 main echinoderm classes

Answer 9

1. Asteroidea
2. Crinoidea
3. Holothuroidea

Question 10

class asteroidea

Answer 10

sea stars/starfish, walk on tube feet, predatory

Question 11

class crinoidea

Answer 11

sea lilies, feather stars, oral side faces up, suspension feeders

Question 12

sea lilies

Answer 12

stalked and mostly sessile crinoids

Question 13

feather stars

Answer 13

crinoids that lack stalks and walk using arms

Question 14

class holothuroidea

Answer 14

sea cucumbers, secondarily bilaterally symmetrical, tube feet around mouth elaborated as feeding tentacles, skeleton reduced to scattered ossicles

Question 15

larval cloning

Answer 15

echinoderms important models for studies of deuterostome-style development

Question 16

phylum chordata 4 synapomorphies

Answer 16

1. notochord
2. dorsal hollow nerve cord
3. pharyngeal slits/clefts
4. muscular post-anal tail

Question 17

notochord

Answer 17

flexible rod located dorsally between the digestive tube and the nerve cord, adds stiff but not rigid support along body, present in all chordate embryos and some adults (adults of most vertebrates reduced to pads between
vertebrae)

Question 18

dorsal hollow nerve cord

Answer 18

unique to chordates (nerve cords in other animals are
solid, ventral), develops from plate of ectoderm dorsal to notochord, plate rolls into tube during embryonic development, anterior portion develops into brain
in most chordates

Question 19

pharyngeal slits/clefts

Answer 19

slits connect pharynx (posterior to mouth) to external
environment, function as suspension-feeding devices in many invertebrate chordates, in aquatic vertebrates, are
gill slits, in terrestrial vertebrates pharyngeal clefts do not turn into slits, but the homologous pharyngeal pouches are important in structuring parts of head and neck

Question 20

muscular post-anal tail

Answer 20

most adult chordates have muscular tail posterior to anus (most non-chordates have digestive tract that extends nearly whole length of body), tail provides propulsive force in swimming species

Question 21

segmentally arranged muscles

Answer 21

present in all chordates except Urochordata, develop from blocks of mesoderm along notochord, arranged in chevrons, contraction causes notochord to flex from side to side (swimming), thus chordates are segmented

Question 22

2 groups invertebrate chordates

Answer 22

1. cephalochordata (25)

2. urochordata (1250)

Question 23

cephalochordata

Answer 23

lancelets, amphioxus, marine, suspension feeders

Question 24

urochordata

Answer 24

tunicates, salps, marine, adults are mostly sessile suspension feeders, tadpole larvae have all 4 synapomorphies and are active swimmers with muscular tail, adult has enormous pharyngeal basket with many slits, some planktonic, some permanently in larval form (paedogenesis)

Question 25

paedogenesis

Answer 25

attaining reproductive adulthood while retaining morphology of juvenile