Zoology Test 3b

Question 1

What does Echinodermata literally mean?

Answer 1

“spiny skin” - endoskeleton of dermal ossicles with projecting spines
- made of calcium carbonate

Question 2

Echinodermata diversity

Answer 2

• not particularly large (in term of species) about 6000 living species
• very important to ecology and evolution
• abundant in marine ecosystems
• humans are more closely related to echinoderms than to any other invertebrate group

Question 3

symmetry of echinoderms

Answer 3

• radially symmetrical
• but have larval echinoderms have bilateral symmetry
• tells us that radial symmetry is secondarily derived
• secondary radial symmetry; evolved from bilateral ancestor, but evolved back to radial

Question 4

nervous system in echinoderms

Answer 4

• cephalization is reduced or absent in this group
• nervous system is decentralized
• no brain

Question 5

feeding habits of echinoderms

Answer 5

• feed on small organic particles or algae, small prey
• some however are efficient predators despite lack of central nervous system and cephalization
• most are active, mobile animals

Question 6

water vascular system in echinoderms

Answer 6

• unique organ to echinoderms
• tube feet for locomotion
• functions in respiration, locomotion and excretion
• water flow: madreporite to internal system of canals to ampulla and tube feet
• stone canal > ring canal > radial canal > lateral canal > ampulla > tube foot

Question 7

coelom in echinoderms

Answer 7

• functions in circulation, respiration and excretion

- fluid circulated by cilia on peritoneum lining eucoelom

Question 8

excretion and gas exchange in echinoderms

Answer 8

• done via papulae and tube feet which project out between ossicles

Question 9

endoskeleton of echinoderms

Answer 9

• dermal ossicles: little bony plates under skin, joined by connective tissue
• some project outward as spines

Question 10

pedicillariae

Answer 10

• small pincers extending from skin
• clean skin of debris, protect papular, may aid in foo capture
• in sea stars and urchins only

Question 11

osmoregulation in echinoderms

Answer 11

• no specialized structure
• restricted to marine ecosystems
• therefore at equilibrium all the time

Question 12

reproduction in echinoderms

Answer 12

• mostly dioecious
• autotomy is common
• con regenerate complete organism with one arm and 1/5th of oral disc

Question 13

autotomy

Answer 13

means that they loose a leg….

Question 14

Crinoidea

Answer 14

• original, oldest
• only way to explain radial symmetry
• sea lilies and feather stars

Question 15

characteristics of sea lilies and feather stars

Answer 15

• both start out attached to substrate via stalk, and continue much of life sessile, but adult feather stars detach and can swim
• arms are tentacle-like with leathery skin and small branched and mucus for trapping and eating suspended phytoplankton

Question 16

Classes of Echinoderm

Answer 16

• Crinoidea
• Asteroidea
• Echinoidea
• Ophiuroidea
• Holothuroidea

Question 17

types of Crinoidea

Answer 17

• sea lily

- feather star

Question 18

types of Asteroidea

Answer 18

• starfish or sea star

Question 19

types of Echinoidea

Answer 19

• sea urchin

- sand dollar

Question 20

types of Ophiuroidea

Answer 20

• brittle stars

- basket stars

Question 21

types of Holothuroidea

Answer 21

sea cucumbers

Question 22

feeding in Asteroidea

Answer 22

• predators: feed on crustaceans, polychaetes, small fish and other sea stars
• eversible stomach: insert cardiac stomach into open bivalve shell to digest and absorb soft parts

Question 23

tube feet in Asteroidea

Answer 23

• used for locomotion and gripping bivalve shells so that shells can be pulled open

Question 24

major body modifications in Echinoidea - sea urchins

Answer 24

• oral surface has expanded around to the aboral side
• fused dermal ossicles form rigid test with long, movable spines, tube feet and pedicellariae
• can live up to 200 yo

Question 25

feeding of Echinoidea

Answer 25

• grazers: feed on algae, detritus or small particles of food, although some feed on larger prey
• Aristotle’s lantern

Question 26

body modifications and feeding in Echinoidea - sand dollars

Answer 26

• very small spines used to burrow just below sand
• fused dermal ossicles form rigid test, with tube feet, and pedicellariae
• organic particles settle on aboral surface, and cilia move them down to mouth

Question 27

feeding in Ophiuroidea

Answer 27

• abundant in ocean, often covering sea bottom
• detritivores
• feeding done via moveable jaws

Question 28

detritivores

Answer 28

feed on decaying matter and plankton

Question 29

how do brittle stars differ from sea stars?

Answer 29

• locomotion by movable arms (no tube feet)
• incomplete digestive system
• no pedicellariae or papullae
• autotomy and regeneration even better developed than in sea stars - they lose arms easily and grow them back readily

Question 30

papullae

Answer 30

peritoneum that sticks up through holes in ossicles

Question 31

how do Holothuroidea differ from other echinoderms?

Answer 31

• greatly elongated on oral-aboral axis
• ossicles reduced so body is relatively soft, use a hydrostatic skeleton
• arrangement of tube feet modified for crawling

Question 32

feeding in Holothuroidea

Answer 32

• feed by picking up food or trapping food on tentacles and stuffing them into mouth one by one
• to defend themselves, they expel parts of viscera which are sticky may contain toxins
• can “throw up” digestive system to distract predator while they get away - regenerates in 3 months

Question 33

protostome

Answer 33

• Annelids, molluscs, arthropods
• blastula embryo, mouth forms first and then anus forms
• spiral cleavage occurs in development
• coeolom forms differently
• a mosaic embryo is formed

Question 34

mosaic embryo

Answer 34

if a cell is taken away from the embryo, then that individual cell will die. needs entire embryo to survive

Question 35

deuterostome

Answer 35

• echinoderms, hermichordates, chordates
• blastula embryo, anus forms first and then mouth forms
• radial cleavage occurs in development
• coeolom form differently
• a regulative embryo is formed

Question 36

regulative embryo

Answer 36

if a cell is taken away, then that cell can continue to develop on its own without the embryo. forms its own embryo —-> twins