Lecture 20: Echinoderms, Hemichordates, Chordates

Question 1

what makes a deuterostome?

Answer 1

• “mouth second”
• some are segmented
• internal segments
• monophyletic

Question 2

ancestral deuterostomes: homalozoans

Answer 2

-have traits that we see in echinoderms and chordates (indicates that they branched off of each other after homalozoans).

Question 3

echinoderms

Answer 3

• pentaradial symmetry in adults
• characterized by internal skeleton
• very closely related to us.

Question 4

pentaradial symmetry

Answer 4

-5 axes of symmetry or multiple of 5

Question 5

echinoderm larvae

Answer 5

-have bilateral larvae

Question 6

water vasculature system

Answer 6

• water filled canals leading to the tube feet

- used for feeding, gas exchange, locomotion

Question 7

madreporite and tube feet

Answer 7

• “mother pore”
• water flows into ring canal and circulated throughout each tube foot
• tube feet also used for attachment

Question 8

oral surface

Answer 8

• headless bc bilateral

- it’s underneath (what they crawl on)

Question 9

aboral surface

Answer 9

opposite of oral surface

Question 10

asexual reproduction in echinoderms

Answer 10

-form of regeneration, many can regenerate lost parts

Question 11

sexual reproduction in echnioderms

Answer 11

-gametes released into water (external fertilization)

Question 12

extinct echinoderms

Answer 12

-20 classes are extinct

Question 13

three groups of echinoderms

Answer 13

• crinoids
• echinozoans
• asterozoans

Question 14

crinoids

Answer 14

types: sea lilies and feather stars

Question 15

asterozoans

Answer 15

types: sea stars and brittle stars

Question 16

sea lilies

Answer 16

• don’t move

- have main body and a bunch of arms

Question 17

feather stars

Answer 17

-attach to surface with arms, can walk/swim

Question 18

sea stars

Answer 18

• type of starfish
• a very important predator
• live in a range of marine environments

Question 19

brittle stars

Answer 19

• thinner arms made of jointed hard plates
• arms are flexible and have no “suckers”
• largest group of living echinoderms
• nocturnal, can freely swim

Question 20

echinozoans

Answer 20

-types: sea cucumbers, sea urchins, sand dollars

Question 21

sea cucumber

Answer 21

• harmless, genetically similar to all other echinoderms

- when you cut it open, you can its pentaradial symmetry

Question 22

sea urchin

Answer 22

• ball and socket joint connected spines
• allows them to rotate
• they pivot/sting threats

Question 23

sand dollar

Answer 23

• flattened disk

- pentamerous

Question 24

hermichordates

Answer 24

• sister taxa to echinoderms
• have a 3 part body plan
• types: acorn worm (up to 2m long)

Question 25

chordate traits

Answer 25

- dorsal Hollow nerve cord - notochord - pharyngeal gill slits - post-anal tail - All seen best during embryonic development

Question 26

dorsal hollow nerve cord

Answer 26

- runs beneath dorsal surface | - develops into brain and spinal nerve cord

Question 27

notochord

Answer 27

- place just above gut and just below dorsal hollow nerve cord - plays a role in nervous system development or becomes part of the vertebral column

Question 28

pharyngeal gill slits

Answer 28

- connects pharynx to external environment and allows us to swallow - pouches never open on terrestrial vertebrates - it's an ancestral trait that was lost in echinoderms but present in chordates

Question 29

post-anal tail

Answer 29

-have it at some point in development every chordate has a tail protruding away from the anus

Question 30

chordate segmentation

Answer 30

-all chordates are segmented

Question 31

non-vertebral chordate groups

Answer 31

-lancelets and tunicates

Question 32

non-vertebral chordate larvae and chordate traits

Answer 32

-the larvae have gill slits, notochord, dorsal hollow nerve cord, and post-anal tail

Question 33

lancelets

Answer 33

-small, notochord helps them burrow

Question 34

tunicates

Answer 34

- aka sea squirts - vary in size - many form colonies through asexual budding