This document describes the phyla Chaetognatha, Echinodermata, and Hemichordata. It provides details on their body forms, characteristics, classes, and examples. Some key points include: Chaetognaths are small marine arrow worms that are predators of plankton. Echinoderms have a calcareous endoskeleton and pentaradial symmetry, and include sea stars, sea urchins, sea cucumbers, and sea lilies. Hemichordates are small marine bottom dwellers that possess gill slits and a rudimentary notochord, and include acorn worms and colonial pterobranchs.

1. Chaetognaths,
Echinoderms,
Hemichordates
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2. Phylum Chaetognatha
Arrow worms
- Name translates to hairy jaws
- All marine and pelagic
- 130 species
- 1-12 cm in length
- Predators within planktonic communities
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3. 3

4. Phylum Chaetognatha
Body Form
- Small, straight bodies
- Dart-like
- Head, unsegmented trunk, and post-anal tail
- Not protostome or deuterostome
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5. Phylum Chaetognatha
Body Form
- Body wall
- Thick cuticle covers body
- Single layer of epidermal cells (except on sides)
- Coelom is well developed
- Used as hydrostatic skeleton
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6. Phylum Chaetognatha
Body Form
- Movement
- Highly mobile and effective predators
- Fins off of trunk make the individuals
very mobile and effective predators
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7. Phylum Chaetognatha
Body Form
- Feeding and digestion
- Predators of copepods, fish, and other
plankton
- Teeth are chitinous spines on the head
- Used for capturing prey
- Complete digestive tract
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8. Phylum Chaetognatha
Form and Function
- Circulation
- Poorly developed
- Nervous system
- Well developed
- Eyes, sensory bristles, may detect
vibrations
- Reproduction
- Monoecious
- Eggs are planktonic
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9. Phylum Xenoturbellida
First described in 1949
- Taxonomic vagabonds
- Two species known
- Live in North Sea mud and feed on bivalves and
bivalve eggs
- Few distinct morphological characters
- Lack cephalization
- No gonads, but sexual reproduction does
occur
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10. 10

11. Phylum Echinodermata
Prickly skin
- All marine
- Possess a calcareous
endoskeleton
- Possess a water vascular system
- Modification of the coelom
- Pedicellariae
- Dermal branchiae
- Pentaradial symmetry in adults
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13. Phylum Echinodermata
Pentaradial symmetry is derived
- Ancestral condition likely bilateral
- Became radially symmetrical with
sessile lifestyle
- Pentaradial symmetry evolved after
Most are benthic
- A few are pelagic
All osmoconformers
- Rarely leave salt water or brackish
waters
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14. 14

15. Phylum Echinodermata
Class Asteroidea
- 1,500 species
- May be very abundant in some
coastal waters
- Especially rock coasts
- Ecologically important predators
- May be top predator with keystone
effects
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16. Phylum Echinodermata
Class Asteroidea - Form and Function
- General body plan
- Aboral and oral surfaces
- Mouth on oral surface
- Madreporite plate on aboral
- Central disc gradually merges with arms
- Body flattened, and covered with a ciliated, pigmented
surface
- Ambulacra run from mouth to tips of arms
- Along ambulacral grooves are tube feet (podia)
- Pedicellariae are present
- Dermal branchiae present
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17. Phylum Echinodermata
Class Asteroidea - Form and Function
- General body plan
- Aboral and oral surfaces
- Mouth on oral surface
- Madreporite plate on aboral
- Central disc gradually merges with arms
- Body flattened, and covered with a ciliated, pigmented
surface
- Ambulacra run from mouth to tips of arms
- Along ambulacral grooves are tube feet (podia)
- Pedicellariae are present
- Dermal branchiae present
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18. Phylum Echinodermata
Class Asteroidea - Form and Function
- Exoskeleton
- Derived from mesoderm
- Ossicles
- Small, calcareous plates
- Catch collagen
- Can change form from liquid to solid based on nerve
impulses
- Allows for holding posture without muscular
effort
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19. Phylum Echinodermata
Class Asteroidea - Form and Function
- Coelom, excretion, respiration
- Gas exchange and excretion of metabolic
wastes done by diffusion
- Coelom present and fluid-filled
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20. Phylum Echinodermata
Class Asteroidea - Form and Function
- Water vascular system
- Purpose - used as a hydrostatic skeleton
- Arrangement of components
- Madreporite plate
- Stone canal
- Ring canal
- Radial canal
- Lateral canal
- Tube feet (with ampulla)
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21. Phylum Echinodermata
Class Asteroidea - Form and Function
- Water vascular system
- Purpose - used as a hydrostatic skeleton
- Arrangement of components
- Functional operation
- Muscle pressure forces water along system
- Water squeezed from ampulla to tube foot to extend
- Relaxing causes water to flow from tube foot to
ampulla
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22. Phylum Echinodermata
Class Asteroidea - Form and Function
- Feeding and digestion
- Voracious predators
- Bivalves especially
- Stomach expelled from body
- Food partially digested and consumed outside of
body
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23. Phylum Echinodermata
Class Asteroidea - Form and Function
- Nervous system
- Three units
- Oral
- Deep
- Aboral
- All connected by epidermal nervous system
- Senses are poorly developed
- Photosensitive ‘eyes’ may be present at tips of arms
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24. Phylum Echinodermata
Class Asteroidea - Form and Function
- Reproduction, regeneration, autotomy
- Most are dioecious
- External fertilization
- Lost arms may be regenerated
- Damaged arms may be shed
- Single arm with part of central disc may regenerate entire
animal
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26. Phylum Echinodermata
Class Ophiuroidea
- Brittle stars
- Largest group of echinoderms
(2,000 species)
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27. Phylum Echinodermata
Class Ophiuroidea - Form and Function
- Similar to Asteroidea, but…
- Rays more slender
- Pedicellariae lacking
- Dermal branchiae lacking
- Ambulacral grooves covered
- Ampullae and suckers on tube feet
lacking
- Madreporite on oral side
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28. Phylum Echinodermata
Class Ophiuroidea - Form and Function
- Similar to Asteroidea, but…
- Rays more slender
- Pedicellariae lacking
- Dermal branchiae lacking
- Ambulacral grooves covered
- Ampullae and suckers on tube feet
lacking
- Madreporite on oral side
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29. Phylum Echinodermata
Class Ophiuroidea - Form and Function
- Feeding and digestion
- Most are scavengers or particle feeders
- A few are carnivorous
- More retreating than asteroids
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31. Phylum Echinodermata
Class Echinoidea
- Sea urchins and sand dollars
- 950 species
- Body enclosed by endoskeleton or
test
- Arms lacking, but pentaradial
symmetry still evident
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32. Phylum Echinodermata
Class Echinoidea - Form and Function
- Ambulacral regions are expanded
and cover the oral surface
- Widely distributed
- Regular echinoids - radial symmetry;
live in rocky waters
- Irregular echinoids - bilateral symmetry;
live in sand waters
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33. Phylum Echinodermata
Class Echinoidea - Form and Function
- Pedicellariae - present and stalked
- Teeth - used for grazing on algae
- Aristotle’s lantern
- Madreporite plate is aboral
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34. Phylum Echinodermata
Class Echinoidea - Form and Function
- Pedicellariae - present and stalked
- Teeth - used for grazing on algae
- Aristotle’s lantern
- Madreporite plate is aboral
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36. Phylum Echinodermata
Class Holothuroidea
- Sea cucumbers
- 1150 known species
- Elongate along oral-aboral axis
- Ossicles are present in body wall,
but much reduced
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37. Phylum Echinodermata
Class Holothuroidea - Form and
Function
- Tube feet
- Restricted to side that contacts
substrate (sole)
- Coelom - fluid-filled and acts as
hydrostatic skeleton
- Respiratory tree - attaches to
cloaca
- Water pumped in for gas exchange
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38. Phylum Echinodermata
Class Holothuroidea - Form and
Function
- Cuvierian tubules - expelled from
cloaca
- Adhesive and thought to function as
defense
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39. Phylum Echinodermata
Class Crinoidea
- Sea lilies and feather stars
- 625 species
- Fossil record has more species
than are currently extant
- A group in decline
- Sessile during much of life
- Lack madreporite plate
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40. Phylum Hemichordata
Marine, vermiform bottom dwellers
- 85 species are known
- Possess gill slits, but also a
rudimentary notochord
- Notochord is not homologous to
that of true chordates
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41. Phylum Hemichordata
Two classes are recognized
- Enteropneusta - acorn worms
- Pterobranchia - no common name
Widely distributed, but secretive
- Many live in burrows or under
rocks
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42. Phylum Hemichordata
Class Enteropneusta
- Body is mucus-covered
- Divided into three regions
- Proboscis
- Collar
- Trunk
- Proboscis is active part of animal
- Probes surroundings for food
- Diggs burrows
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43. Phylum Hemichordata
Class Enteropneusta
- Feeding and Digestion
- Ciliary-mucus feeders
- May feed on deposits on seafloor
- May also filter particles from water
- Food captured on proboscis moved to
mouth at base of collar
- Pharynx, esophagus, intestine
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44. Phylum Hemichordata
Class Enteropneusta
- Respiration
- Fresh water brought in via ciliary tracts
- Passes through gill pores
- Some gas exchange is cutaneous
- Circulation
- Open circulatory system
- Middorsal vessel leads to network of
blood sinuses
- Poor oxygen carrying capacity
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45. Phylum Hemichordata
Class Enteropneusta
- Nervous system
- Both dorsal and ventral nerve cords
- Dorsal cord is hollow as in chordates
- Networks of nerve fibers in skin
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46. Phylum Hemichordata
Class Enteropneusta
- Reproduction and Development
- Dioecious
- Sexual reproduction is the norm
- Fertilization is external
- Development is mostly direct
- But some is indirect (tornaria
larvea)
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47. Phylum Hemichordata
Class Pterobranchia
- 20 living species
- Sedentary and colonial
- Colonial individuals live in tubes
- Use tentacles with cilia for
gathering food - lophophore
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48. Phylum Hemichordata
Class Pterobranchia
- Proboscis, collar, and trunk present
- More monoecious members than
Enteropneusta
- But some still dioecious
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