1. Vertebrates
Chapter 34

3. Chordates Bilateral symmetry Notochord Jointed appendages Segmentation
Birds, reptiles, amphibians, fishes, & mammals

4. Chordates Common features of chordates
Present at some point in development
1. Nerve cord
Hollow
Ectoderm
Beneath dorsal surface
Vertebrates (brain & spinal cord)

5. Chordates 2. Notochord Dorsal side of primitive gut in embryo
Fluid filled cells
Enclosed in stiff fibrous tissue
Persists in some
Support
Reduced to vertebral discs in others

6. Chordates 3. Pharyngeal slits: Connect pharynx & esophagus to outside
Gills stay connect to outside
Pharyngeal pouches:
Slits do not connect to outside
Terrestrial vertebrates
Present in embryos
4. Postanal tail
At least during embryo development

8. Chordates Humans Nerve cord stays
Notochord is replaced by spinal column (discs)
Pharyngeal pouches are lost
Except one forms Eustachian tube
Tail regresses tail bone

9. Chordates Other features Muscles arranged in segmented blocks
Work against internal skeleton
Helps movement

10. Chordates Phylum Chordata includes three subphyla, Vertebrates
Two phyla of invertebrates
Urochordates
Cephalochordates.

11. (sister group to chordates)
Fig. 34-2
Echinodermata
(sister group to chordates)
Cephalochordata
(lancelets)
ANCESTRAL
DEUTERO-
STOME
Chordates
Urochordata
(tunicates)
Notochord
Myxini
(hagfishes)
Common
ancestor of
chordates
Craniates
Petromyzontida
(lampreys)
Head
Chondrichthyes
(sharks, rays, chimaeras)
Vertebrates
Vertebral column
Actinopterygii
(ray-finned fishes)
Gnathostomes
Jaws, mineralized skeleton
Actinistia
(coelacanths)
Osteichthyans
Lungs or lung derivatives
Lobe-fins
Dipnoi
(lungfishes)
Lobed fins
Amphibia (frogs,
salamanders)
Legs
Reptilia
(turtles, snakes,
crocodiles, birds)
Tetrapods
Amniotes
Amniotic egg
Mammalia
(mammals)
Milk

12. Chordates Nonvertebrates Notocord but no backbone
Tunicates (urochordates)
Marine, shallow waters
Sessile
Adults no cavity or segmentation
Tadpole shows characteristics
Tunic: sac of cellulose secreted by adults
Surrounds the animal

14. Chordates Lancelets (cephalochordata) Shallow waters in ocean
Buried in sand
Anterior end sticking out
Plankton
Gill slits
Closest relative to vertebrate

15. (a)
(b)
Fig. 34.4

16. Vertebrates 1. Vertebral column 2. Head
Brain is enclosed in a bony skull or cranium
Craniate chordates

17. Vertebrates Other characteristics 1. Neural crest
Cells that develop on crest of neural tube
Form other structures (teeth, neurons, dermis)
2. Internal organs
Liver, kidney, endocrine glands
3. Endoskeleton
Cartilage & bone helps with movement

18. Neural crest

19. Neural crest Dorsal edges of neural plate Neural crest Neural tube
Fig. 34-7
Neural crest
Dorsal edges
of neural plate
Neural
crest
Neural
tube
Migrating neural
crest cells
Figure 34.7 The neural crest, embryonic source of many unique craniate characters
Notochord

20. Vertebrates 470 mya Jawless fish Jaw developed Gave rise to Amphibians
Were first vertebrate moved to land
First reptiles 300 mya
Birds (descendants of dinosaurs)
Mammals 220 mya

21. Vertebrates 65 mya dinosaurs disappeared Gave rise to larger mammals
Nine classes of vertebrae
5 fish (2 are extinct)
4 tetrapods (animals with 4 limbs)
Amphibians, reptiles, birds, mammals

24. Fish Marine & freshwater 1. Vertebral column
2. Jaws & paired appendages
Helps eat larger & active prey
Paired fins help with swim

25. Fish 3. Gills Extract oxygen dissolved in water Vessels rich in blood
Supported by cartilage
4. Single-loop blood circulation
Blood pumped from heart to gills
Oxygenated blood to body
Returns to heart

26. Fish evolution First fish jawless Internal skeleton made of cartilage
Sucked up small food particles
Hagfish: Present day jawless fish

27. Fig

28. Fish Jaw 410 mya Cartilage, supported gills Teeth evolved
Spiny fish with scales had bone
No longer exist
Bony & sharks developed next
Sharks dominated for awhile

29. Fish Skeleton cartilage with calcium carbonate Lighter skeleton
Shark teeth first to be developed
Not firmly attached so fall out easily
Reproduction advanced with internal fertilization
Most females give birth to pups

30. Fish Bony fish Cartilage is replaced by bone Ossification
Early fish evolved in freshwater unlike shark
First bony fish were small
Fins of thin scales
Symmetrical tails

31. Fish Bony fish most dominant Swim bladder
Gas filled sac-keeps them floating
Sharks have to keep moving or they sink
Lateral line system
Helps fish detect movement of objects
Helps orient the fish
Gill cover

32. Swim bladder Dorsal fin Adipose fin (characteristic of trout) Caudal
Fig
Swim
bladder
Dorsal fin
Adipose fin
(characteristic
of trout)
Caudal
fin
Spinal cord
Brain
Nostril
Cut edge
of operculum
Anal fin
Liver
Lateral
line
Gills
Anus
Heart
Gonad
Stomach
Urinary
bladder
Pelvic
fin
Kidney
Intestine

33. Fig

34. Fig
Bones
supporting
gills
Tetrapod
limb
skeleton

35. Amphibians First vertebrae to walk on land Descendants of fish Small
More species than mammals
Frogs, salamanders & caccileans
Key role in terrestrial food chains

37. Amphibians Characteristics 1. Legs 4 legs helps movement (tetrapods)
2. Cutaneous respiration
Respiration occurs across their skin
Moist skin
3. Lungs
Pair of lungs, poorly developed
Lower mouth-suck in air

38. Amphibians 4. Pulmonary veins Return aerated blood to heart
Re-pumps to body
5. Partially divided heart
Two chambers separated
Prevents un-aerated/aerated blood mixing

39. Amphibian evolution Amphibia Greek “both lives”
Evolved from lobe-finned fish
Adaptations due to movement on land
1. Legs
2. Lungs
3. Heart
4. Reproduction
5. Keep body from drying out

40. Amphibians 370 mya in Greenland Present day 3 orders Anura
Frogs & toads
Frogs smooth, moist skin, long hind legs
Live in or near water
Toads dry skin, short legs
Reproduce in water (tadpoles)
Eggs fertilized externally

42. Amphibians Urodela (Caudata) Salamanders Long tails, moist skin
Fertilization external, eggs in water
Apoda
Tropical burrowing amphibians
Resemble worms

43. Fig

44. Reptiles

46. Reptiles Characteristics 1. Amniotic egg (Amniotes)
Chorion: outer layer of egg
Below shell (gas exchange)
Amnion: encases the embryo (cushions)
Yolk sac: supplies food (blood supply)
Allantois: surrounds a cavity in which wastes from the embryo goes

48. Fig

49. Reptiles 2. Dry skin Watertight skin Scales 3. Thoracic breathing
Expand & contract rib cage
Pulls air into lungs

50. Reptiles
Evolution
4 major groups of reptiles dominated for 250 million years
Dinosaurs
Present day reptiles
Turtles, lizards, snakes, & crocodiles

51. (d) Eastern box turtle (Terrapene carolina carolina)
Fig d
(d) Eastern box turtle (Terrapene
carolina carolina)

52. Reptiles Other characteristics Internal fertilization
4 chambered heart
Ectothermic:
Body temperature determined by environment
Regulate temperature by behavior

53. Birds

54. Toothed beak Wing claw Airfoil wing with contour feathers
Fig
Toothed beak
Wing claw
Airfoil wing
with contour
feathers
Long tail with
many vertebrae

55. Birds Birds successful due to structure of the feather
Derived from reptilian scales
Bones are thin
Hollow

58. Birds Bird’s anatomy modified to enhance flight. Reduce weight
Missing of some organs.
Females-only one ovary.
Modern birds-toothless
Grind food in a muscular gizzard
Near stomach.

59. Birds Descended from dinosaurs Adaptations 1. Efficient respiration
2. Efficient circulation
3. Endothermy
Generate heat internally
4. Amniotic egg

60. Mammals

62. Mammals 5300 living species Smallest # of species of vertebrae
Characteristics
1. Mammary glands
Newborns nurse
Milk is rich in fat, sugar, protein, vitamins & minerals

63. Mammals 2. Hair Consists of protein Sensitive to touch (cat)
Avoid colliding with objects
3. Endothermy
Fat layer under skin
4. Placenta
Carry & nourish babies

64. Mammals
5. Teeth
Variety of teeth to match diet
6. Middle ear

65. Articular Temporal fenestra Quadrate Dentary Jaw joint Squamosal
Fig
Key
Articular
Temporal
fenestra
Quadrate
Dentary
Jaw joint
Squamosal
(a) In Biarmosuchus, an early synapsid, the articular and
quadrate bones formed the jaw joint.
Middle ear
Eardrum
Middle ear
Eardrum
Stapes
Inner ear
Inner ear
Stapes
Incus (quadrate)
Sound
Sound
Malleus (articular)
Present-day reptile
Present-day mammal
(b) In mammals, the articular and quadrate bones are incorporated into the middle ear.

66. Mammals 1. Egg-laying Monotremes: duck-billed platypus
Found in Australia
2. Marsupials
3. Placental mammals

67. Marsupials