Deuterostomes

Question 1

Define Deuterostomes?

Answer 1

Triploblastic, true coelomate animals with internal skeletons.

Question 2

What are the 3 main clades of Deuterostomes?

Answer 2

Echinoderms (Sea stars, sea urchins), Hemichordates (Acorn worms and pterobranchs), Chordates (Sea squirts, lancelets and vertebrates)

Question 3

What developmental patterns do Deuterostomes show?

Answer 3

Blastopore becomes the anus and mouth forms on opposite side, coelom develops from mesodermal pockets that bud off from gastrula cavity, radial cleavage, indeterminate cleavage.

Question 4

What is radial cleavage?

Answer 4

Cells cleave parallel or perpendicular to animal – vegetal axis.
Cells lie beside and on top of each other.

Question 5

What is Indeterminate development?

Answer 5

Cells separated after first divisions still develop into complete embryos
Identical twins

Question 6

What are traits common of Echinodermata?

Answer 6

Radial symmetry as adults, bilateral symmetry as larvae, pentardial symmetry, calcified internal plates, loss of pharyngeal silts. Ciliated larvae.

Question 7

What is the typical Echinodermata body plan?

Answer 7

No head, move equally well in many directions, oral side containing the mouth and aboral side containing the anus.

Question 8

List some characteristics of echinodermata?

Answer 8

Pelago-benthic life cycle, reproduce mostly sexually, generally dioecious, external fertilisation, splitting (transverse fission) parthenogenesis, autotomy and regeneration of parts, no specialised excretory organs in adults.

Question 9

What two evolutionary innovations do Echinodermata posses?

Answer 9

Endoskeleton, internal and calcified skeleton.

Water Vascular System.

Question 10

Describe the Sea Urchin Endoskeleton?

Answer 10

Endoskeleton beneath epidermis, composed of small calcareous plates “ossicles”.
Skeletal plates connected by collagen which can be stiff or flexible “catch collagen”.
Unique mechanical support which controls body without muscles and holds posture.

Question 11

What is the water vascular system?

Answer 11

Network of water filled canals leading to extensions (tube feet)

Question 12

What is the function of the WVS?

Answer 12

forms hydraulic system for locomotion, gas exchange and feeding.

Question 13

How does the WVS work?

Answer 13

Due to water pressure, water enters through the madreporite, which is connected to the ring canal around the esophagus, then into the rays through radial canals, and finally into the tube feet.

Question 14

How do tube feet work?

Answer 14

Lack circular muscles, fluid pumped into foot by contraction of ampulla, one-way valve at junction of ampulla/radial canal, tube foot retracts when longitudinal muscles in each tube foot contract.

Question 15

What belongs to Asteroidea?

Answer 15

Sea Stars (regenerative powers, predators, gonads and digestive organs located in arms, Everts stomach)

Question 16

What is Macrophagous feeding?

Answer 16

When the stomach is everting externally.

Question 17

What is the function of Pedicellariae in Sea Stars?

Answer 17

Keep body surface clear of algae in conjunction with the ciliated epidermis present present in all echinoderms.

Question 18

What are Pedicellariae?

Answer 18

a defensive organ like a minute pincer

Question 19

How do Pedicellariae work?

Answer 19

Possess movable vesicles and opening and closing muscles.

Question 20

What mechanisms of defence do Echinodermata possess?

Answer 20

Thorns, sometimes with neurotoxins.

Question 21

What belongs to Echinoidea?

Answer 21

Sea Urchins and Sand Dollars.

Question 22

What are common characteristics of Echinoidea?

Answer 22

Spherical, free living, lack arms & appendages, posses spines (movable for locomotion & contain toxins for defence), pedicellaria, Catch plankton with their tube feet or scrape algae from rocks with a rasping structure

Question 23

What is unique of Aristotle’s Lantern?

Answer 23

Composed of 50 skeletal elements; worked by 60 muscles, 2 powerful blocks of muscle between pyramids close jaws and provide strong biting action.

Question 24

What belongs to Crinoidea?

Answer 24

Sea lilies, feather stars

Question 25

What are common characteristic of Crinoidea?

Answer 25

Sea lilies attach to substrate by a stalk
Feather stars grasp substratum with flexible appendages allowing limited movement
Tube feet ONLY for food collection, gas exchange & excretion

Question 26

What belongs to Ophiuroidea?

Answer 26

Brittle stars, Basket Stars

Question 27

What belongs to Holothuroidea?

Answer 27

Sea Cucumber

Question 28

What features are common of Sea Cucumbers?

Answer 28

Scavengers, soft-bodied, lack arms, bilateral symmetry, anterior tube feet, unique defence.

Question 29

What unique defence do sea cucumbers possess?

Answer 29

Some expel cuverian tubules (sticky/toxic) or evisceration (entire digestive system expelled)

Question 30

How are the tube feet of sea cucumbers specialised?

Answer 30

Modified into feathery, sticky tentacles that protrude from the mouth.

Question 31

Recap the evolutionary innovations of Echinodermata?

Answer 31

WVS for locomotion, feeding, excretion & respiration
Endoskeleton – internal calcified skeleton, with catch collagen for unique mechanical support, • Regeneration, defence (spines, pedicellaria, eviseration), grazing apparatus, macrophagous feeding