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Invertebrates > Ambulacraria Lecture 11 > Flashcards

Ambulacraria Lecture 11 Flashcards

1
Q

What two groups make up ambulacrarians?

A

Echinoderms and Hemichordates

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2
Q

Traits of Echinoderms

A

All marine living, benthic

Paleozoic forms: sessile Modern forms: motile

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3
Q

what are the extant classes of Echinoderms (5)

A 
Holothuriodea 
Echinoidea
Crinoidea
Ophiuroidea
Asteroidea
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4
Q

Traits of Crinoidea

A

Sea lilies and feather stars
most ancient class of living echinoderms
mainly deep-water, suspension feeders

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5
Q

Traits of Asteroidea

A

Seastars (all benthic and found at wide range of depths
5-fold symmetry
predators and scavengers
5 arms typical (multiples of 5)

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6
Q

Traits of Ophiuroidea

A

Brittle stars and basket stars
slender arms for locomotion
diverse feeding habits
soft bottom habitats (fragile arms, easily able to regenerate)

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7
Q

Traits of Echinoidea

A

Sea urchins and sand dollars
no arms
skeletal ossicles form the test
pentaradial symmetry

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8
Q

Irregular body form

A 
short spines (locomotion and body clean of sediment)
flattened (secondary bilateral symmetry)
adaptation for burrowing
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9
Q

Regular body form

A 
Long spines (locomotion)
tube feet assist in movement 
Pedicellariae (pincers) cleaning and defense
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10
Q

Traits of Holothuroidea

A

secondary bilateral symmetry (extended on oral-aboral axis)
tentacles and mucous (suspension and deposit feeding)
tube feet for locomotion

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11
Q

Hemichordate classes (2)

A

Pterobranchs

Enteropneusta

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12
Q

Pterobranchia traits

A

tube-dwelling, colonial animals

clear tripartite body

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13
Q

Enteropneusta

A 
Acorn worms (solitary)
Sediment dwelling animals (clear tripartite body)
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14
Q

Ambulacraria Characteristics (3)

A

Tripartite body (three coeloms)
Similar larval forms
Axial Complex

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15
Q

Divisions of Tripartite coelom

A 
Perivisceral coelom (surrounds visceral tissues)
Hydrocoel- (forms water vacular system)- lost in all except Crinoids
Hemal coelom
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16
Q

Hemichordate body plan

A

Proboscis
Collar
Stalk
Protocoel (coelom of the proboscis)

17
Q

Axial complex in Echinoderms and Hemichordates

A

Junction of two coeloms and WVS in Echinoderms
Heart-kidney complex in Hemichordates
(homologous axial complexes used in circulation of fluid and excretory functions)

18
Q

Similar larval forms

A

ciliated
free-swimming
bilateral

19
Q

Uniting features of Echinoderms (6)

A
  1. Calcareous skeleton, of endoskeletal plates
    (skeletal ossicles)- stereom collectively
  2. Pedicellariae (pincers, dorsal side, base of spine)
  3. Dermal branchiae (Papulae) (thin folds between ossicles, gas exchange)
  4. Water Vascular System (tube-feet, podia)
  5. pentaradial symmetry in adults (linked to sessile lifestyle)
  6. Ambulacral grooves (discrete arms with ambulacra on oral surface)- radial canal and primary podia
20
Q

Parts of WVS (4)

A

Primarily for feeding; locomotion arose later
a- madreporite (connected to water)
b-polian vesicles- maintain internal pressure
c- radial canals (5)- extend ambulacral grooves (tube feet rows)
d- lateral canals to tube feet

21
Q

How do tube feet work

A

extended through hydrostatic pressure

retracted via longitudinal muscles

22
Q

Bilateral larvae development

A

left side- into adult (becomes oral plate)

right side- reabsorbed

23
Q

Types of adult body forms (2)

A
  1. Ambularcra on five arms, with clear pentaradial symmetry (Crinoids, asteroidea and Ophiuroidea)
  2. Ambulacra extend from oral-aboral pole, arms absent, variable degree of bilateral symmetry (Echinoidea, Holothuroidea)
24
Q

Echinoderm fossil record

A

Bilateral ancestor
Evolved radial symmetry for sessile lifestyle
stem groups- deuterostome features (ie. gill slits)

25
Q

Phylum Hemichordata

A

Pterobranchia/ Grapolithina
Enteropneusta (acorn worms)
all benthic worm-like, have stomochord and gill slits

26
Q

Hemichordate features

A
  • macroscopic
  • dorsal nerve chord
    stomochord (collar region)
    Tripartite body division
27
Q

Grapolithina

A

similar tubes to Pterobranchs
- sawblade shape of tube
extinct

28
Q

Hemichordates: shared chordate characters (4)

A

gill slits (leading to pharynx)
stomochord (not notochord)- rudimentary collar region
Dorsal nerve chord
Tripartite division of body (Probosics- protcoel, collar region- two coelomic caivites, Trunk- coelomic cavities derived from embryonic metacoel)

29
Q

Closely related to Chordates or Echinoderms?

A

considered more closely related to Echinoderms

Invertebrates (6 decks)

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