1. The Animal Kingdom: The Deuterostomes
Chapter 31

2. Learning Objective 1
What are the shared derived characters of deuterostomes?

3. Deuterostomes 1 Include echinoderms, hemichordates, chordates
Hemichordates (acorn worms)
marine deuterostomes
three-part body (proboscis, collar, trunk)

4. Deuterostomes 2 Shared derived characters
radial, indeterminate cleavage
blastopore becomes anus
larva have a loop-shaped ciliated band used for locomotion

5. KEY CONCEPTS
The echinoderms and the chordates are the two most successful deuterostome lineages in terms of diversity, number of species, and number of individuals

6. Learning Objective 2
What are three shared derived characters of echinoderms?
Describe the main classes of echinoderms

7. Phylum Echinodermata Marine animals with
spiny “skin”
water vascular system
tube feet
endoskeleton
Larvae exhibit bilateral symmetry
Most adults exhibit pentaradial symmetry

8. Sea Star Body Plan

9. Stomach Digestive gland Tube feet Anus Ampulla Spine Gonad Dermal gill
Figure 31.2: Body plan of a sea star.
(a) A sea star viewed from above, with its arms in various stages of dissection. Similar structures are present in each arm. The two-part stomach is in the central disc with the anus on the aboral (upper) surface and the mouth beneath on the oral surface.
Spine
Gonad
Dermal gill
Pedicellariae
Fig. 31-2a, p. 670

10. Class Crinoidea Sea lilies, feather stars oral surface turned upward
some crinoids are sessile

11. Class Asteroidea Sea stars central disc with five or more arms
use tube feet for locomotion

12. Class Ophiuroidea Brittle stars
arms longer, more slender than sea stars
arms more distinct from central disc
use arms for locomotion
tube feet lack suckers

13. Class Echinoidea Sea urchins, sand dollars lack arms
have a solid shell
are covered with spines

14. Class Holothuroidea Sea cucumbers elongated flexible bodies
circle of modified tube feet surrounds mouth

15. Figure 31.1: Echinoderms.
Fig. 31-1, p. 669

16. KEY CONCEPTS
Echinoderms are characterized by radial symmetry in adults, a water vascular system, tube feet, and spiny skin

17. Learning Objective 3
What are five shared derived characters of chordates?

18. Phylum Chordata 1 Subphylum Urochordata Subphylum Cephalochordata
Subphylum Vertebrata

19. Chordate Evolution

20. Phylum Chordata 2 At some time during life cycle have
flexible, supporting notochord
dorsal, tubular nerve cord
pharyngeal (gill) slits
muscular postanal tail
endostyle (or thyroid gland)

21. Chordate Body Plan

22. Dorsal, tubular nerve cord Brain Notochord Postanal tail
Mouth
Pharynx
Anus
Figure 31.4: Generalized chordate body plan.
Note the notochord; dorsal, tubular nerve cord; pharyngeal (gill) slits; and postanal tail.
Pharyngeal (gill) slits
Intestine
Muscular segments
Heart
Fig. 31-4, p. 671

23. KEY CONCEPTS
At some time in its life, a chordate has a notochord; dorsal, tubular nerve cord; pharyngeal slits; and a muscular postanal tail

24. Learning Objective 4
What are the invertebrate chordate subphyla?

25. Subphylum Urochordata
Tunicates
marine animals with tunics
suspension-feeders
Larvae are free swimming
Most adults are sessile

26. Tunicate Body Plan

27. Cephalochordata (lancelets) Echinodermata (sea stars, sea urchins)
Hemichordata (acorn worms)
Urochordata (tunicates)
Vertebrata
Figure 31.5: Tunicate body plan.
Deuterostome ancestor
Fig. 31-5a, p. 672

28. Incurrent siphon Ganglion Oral tentacles Excurrent siphon
Pharynx with slits
Atrium
Endostyle
Tunic
Intestine
Esophagus
Figure 31.5: Tunicate body plan.
Testis
Digestive gland
Ovary
Stomach
Heart
Fig. 31-5b, p. 672

29. Figure 31.5: Tunicate body plan.
0.5 mm
Fig. 31-5c, p. 672

30. Incurrent opening Pharynx with slits Atrium Excurrent opening
Nerve cord
Adhesive papilla
Notochord
Figure 31.5: Tunicate body plan.
Heart
Stomach
Fig. 31-5d, p. 672

31. Subphylum Cephalochordata
Lancelets
small, segmented, fishlike animals

32. Echinodermata (sea stars, sea urchins) Hemichordata (acorn worms)
Cephalochordata (lancelets)
Urochordata (tunicates)
Vertebrata
Figure 31.6: Cephalochordate body plan.
(a) Photograph of a lancelet, Branchiostoma (amphioxus). Note the prominent pharyngeal gill slits. (b) Longitudinal section showing internal structure.
Deuterostome ancestor
Fig (1), p. 673

33. Nerve cord Pharyngeal slits Caudal fin
Tentacles
Nerve cord
Notochord
Pharyngeal slits
Caudal fin
Intestine
Figure 31.6: Cephalochordate body plan.
(a) Photograph of a lancelet, Branchiostoma (amphioxus). Note the prominent pharyngeal gill slits. (b) Longitudinal section showing internal structure.
Tentacles
Endostyle
Atrium
Gonads Atriopore
Anus
Fig (a-b), p. 673

34. Learn more about the body plans of the deuterostomes by clicking on the figures in ThomsonNOW.

35. Learning Objective 5
Discuss the evolution of chordates

36. Evolution of Chordates
Urochordates (tunicates)
probably first chordates to evolve
Subphyla Cephalochordata and Vertebrata
sister taxa (recent common ancestor)

37. Vertebrate Evolution

38. Explore the evolutionary relationships of vertebrates by clicking on the figure in ThomsonNOW.

39. Learning Objective 6
What are four shared derived characters of vertebrates?

40. Vertebrates 1 Vertebral column Cranium Neural crest cells
chief skeletal axis of body
Cranium
braincase
Neural crest cells
determine development of many structures

41. Vertebrates 2 Pronounced cephalization Complex brain
Muscles attached to endoskeleton for movement

42. KEY CONCEPTS
Shared derived characters of vertebrates include a vertebral column, cranium, neural crest cells, and an endoskeleton of cartilage or bone

43. Learning Objective 7
What is the difference between the major groups of jawless fishes?

44. Jawless Fishes 1 Ostracoderms (extinct) Agnathans (hagfishes) Lampreys
among earliest known vertebrates
Agnathans (hagfishes)
class Myxini
Lampreys
class Cephalaspidomorphi

45. Hagfish

46. Lampreys

47. Hagfishes Have no trace of vertebrae
Why are they classified as vertebrates?
Some systematists classify vertebrates plus hagfishes as craniates (Craniata)
But molecular data support classifying hagfishes as vertebrates

48. Jawless Fishes 2 Jaws and paired fins absent Hagfishes Lampreys
in both hagfishes and lampreys
Hagfishes
marine scavengers
secrete slime as a defense mechanism
Lampreys
many are parasites on other fishes

49. Learning Objective 8
Trace the evolution of jawed fishes and early tetrapods
Identify major taxa of jawed fishes and amphibians

50. Class Chondrichthyes (Cartilaginous Fishes)
Includes sharks, rays, skates
Cartilaginous fishes have
jaws
two pairs of fins
placoid scales

51. Cartilaginous Fishes

52. Shark Structure

53. Internal structure of a shark.
Spleen Kidney
Stomach Testis
Gill slits
Clasper
Mouth
Figure 31.12: Anatomy of a shark.
Pelvic fin
Cloaca
Intestine
Pancreas
Heart
Pericardial cavity
Pharynx
Liver
Internal structure of a shark.
Fig a, p. 679

54. Internal structure of a shark.
Kidney
Spleen
Clasper
Cloaca
Pelvic fin
Testis
Stomach
Gill slits
Mouth
Pharynx
Heart
Pericardial cavity
Liver
Intestine
Pancreas
Figure 31.12: Anatomy of a shark.
Internal structure of a shark.
Stepped Art
Fig a, p. 679

55. Enamel Dentine Pulp cavity Epidermis Dermis
Figure 31.12: Anatomy of a shark.
Structure of a placoid scale.
Fig b, p. 679

56. Shark Reproduction Oviparous Ovoviparous Viviparous lay eggs
young enclosed by eggs
incubated in mother’s body
Viviparous
young develop in mother’s uterus
nutrients transferred from mother’s blood

57. Bony Fishes Class Actinopterygii Class Actinistia Class Dipnoi
ray-finned fishes
Class Actinistia
coelacanths
Class Dipnoi
lungfishes

58. Bony Fishes
During the Devonian, bony fishes gave rise to two evolutionary lines:
Actinopterygii (ray-finned fishes)
Sarcopterygii (lobe-finned fishes)

59. Early Jawed Fishes

60. Ray-Finned Fishes Gave rise to modern bony fishes
Lungs modified as swim bladder
air sac for regulating buoyancy

61. Modern Bony Fishes

62. Bony Fish Structure

63. Nerve cord Swim bladder Dorsal fins Kidney Ureter Caudal fin Brain
Nostril
Urinary bladder
Pharynx
Figure 31.13: Perch, a representative bony fish.
The swim bladder is a hydrostatic organ that enables the fish to change the density of its body and remain stationary at a given depth. Pectoral fins (not shown) and pelvic fins are paired.
Gills
Anal fin
Heart
Gonad
Liver
Intestine
Cloaca
Stomach Pelvic fin
Fig , p. 680

64. KEY CONCEPTS
Jaws and fins were key adaptations that contributed to the success of jawed fishes

65. Sarcopterygii Gave rise to lungfishes (class Dipnoi)
coelacanths (class Actinistia)

66. Sarcopterygii Lungfishes gave rise to tetrapods Tiktaalik
land vertebrates
Tiktaalik
transitional between fishes and tetrapods

67. Early Tetrapods Early amphibians mainly aquatic
moved onto land to find food, escape predators
had limbs strong enough to support body weight on land

68. Class Amphibia 1 Salamanders, frogs and toads, caecilians
Most return to water to reproduce
Frogs
embryos develop into tadpoles, which undergo metamorphosis to become adults

69. Insert “Salamander locomotion”
salamander_walk.swf

70. Modern Amphibians

71. Class Amphibia 2 Use moist skin as well as lungs for gas exchange
Have a three-chambered heart
systemic and pulmonary circulations

72. Learn more about jawless, early jawed, cartilaginous, and bony fishes by clicking on the figures in ThomsonNOW.

73. Learning Objective 9
What are three vertebrate adaptations to terrestrial life?

74. Terrestrial Vertebrates
Amniotes
include reptiles, birds, mammals
Amniotic egg (with shell and amnion)
important adaptation for life on land
Amnion (membrane)
forms fluid-filled sac around embryo

75. Amniotic Egg

76. Amnion (protects embryo) Embryo Chorion (encloses entire embryo)
Allantois
(stores wastes in reptiles and birds)
Yolk sac
(encloses yolk, provides nutrients)
Figure 31.19: An amniotic egg.
The amnion is a protective membrane surrounding the embryo. Other extraembryonic membranes are the yolk sac, allantois, and chorion.
Shell
Albumen (provides nutrients)
Fig , p. 683

77. Amniotes Have body covering that retards water loss
Have physiological mechanisms that conserve water

78. Learn more about the amniotic egg by clicking on the figure in ThomsonNOW.

79. Learning Objective 10 Describe reptiles and birds
Give an argument for including birds in the reptile clade

80. Class Reptilia A paraphyletic group
dinosaurs, turtles, lizards, snakes, alligators
Biologists classify amniotes in two main groups: diapsids and synapsids

81. Amniotes Diapsids Synapsids
turtles, ichthyosaurs, tuataras, squamates (snakes and lizards), crocodiles, pterosaurs, saurischian dinosaurs, birds
Synapsids
gave rise to therapsids, which gave rise to mammals

82. Diapsids Many biologists consider birds as feathered dinosaurs
classify birds and most reptiles as diapsids

83. Pelvis Leg Feathers Fig. 31-22b, p. 688
Figure 31.22: Archaeopteryx and Caudipteryx.
Fig b, p. 688

84. Therapsid

85. Amniote Evolution

86. 4 Groups of Extant Reptiles
1. Turtles, terrapins, tortoises

87. 4 Groups of Extant Reptiles
2. Lizards, snakes, amphisbaenians

88. 4 Groups of Extant Reptiles
3. Tuataras

89. 4 Groups of Extant Reptiles
4. Crocodiles, alligators, caimans, gavials

90. Reptile Characteristics 1
Reproduction
internal fertilization
leathery protective shell around egg
embryo develops protective membranes (including amnion)

91. Reptile Characteristics 2
Dry skin with horny scales
Lungs with many chambers
Three-chambered heart
some separation of oxygen-rich and oxygen-poor blood

92. Birds 1 Adaptations for powered flight Four-chambered heart
feathers
wings
light, hollow bones containing air spaces
Four-chambered heart
Very efficient lungs

93. Birds 2 Excrete solid metabolic wastes (uric acid) Endotherms
maintain constant body temperature
Well-developed nervous system
Excellent vision and hearing

94. Modern Birds

95. KEY CONCEPTS
Limbs, a body covering that retards water loss, and the amniotic egg, with its shell and amnion, were key adaptations that contributed to the success of terrestrial vertebrates

96. Learning Objective 11
Contrast monotremes, marsupials, and placental mammals
Give examples of animals that belong to each group

97. Mammals Characterized by
hair
mammary glands
differentiated teeth
three middle-ear bones
Have highly developed nervous system and muscular diaphragm
Are endotherms

98. Monotremes (Subclass Holotheria)
Duck-billed platypus, spiny anteaters
Monotremes lay eggs

99. Marsupials (Subclass Metatheria)
Include pouched mammals
kangaroos, opossums
Young are born in embryonic stage
Complete development in mother’s marsupium
nourished with milk from mammary glands

100. Marsupials

101. Placental Mammals (Subclass Eutheria)
Characterized by placenta
for exchange between embryo and mother

102. Mammal Evolution