1. PowerLecture: Chapter 25 Part I
Animal Evolution – The Invertebrates

2. Characteristics of Animals
Multicelled Aerobic heterotrophic eukaryotes
Most reproduce sexually

3. Animal Origins
Originated during Precambrian (1.2 billion million years ago)

4. Radial Symmetry
radial symmetry
Fig. 25-5a, p.406

5. Bilateral Symmetry dorsal posterior ventral anterior
Fig. 25-5b, p.406

6. Animal Tissues
Ectoderm
Endoderm
Mesoderm

7. The Gut - 2 types Saclike gut Complete digestive system
One opening for taking in food and expelling waste
Complete digestive system
2 Openings; mouth and anus

8. Body Cavities - Acoelomate
epidermis
gut cavity
no body cavity; region between gut and body wall packed with organs
Fig. 25-6, p.406

9. Body Cavities - Pseudocoel
epidermis
gut cavity
unlined body cavity (pseudocoel) around gut
Fig. 25-6, p.406

10. lined body cavity (coelom)
Body Cavities - Coelom
gut cavity
lined body cavity (coelom)
peritoneum
Fig. 25-6, p.406

11. Segmentation Repeating series of body units
Units may or may not be similar
Insects - segments may be fused

12. Segmentation
Fig. 25-8c, p.407

13. Segmentation
Fig. 25-8a, p.407

14. Fig. 25-7, p.407 sponges cnidarians flatworms annelids mollusks
roundworms
arthropods
echinoderms
chordates
coelom reduced
coelom reduced
coelom lost
pseudocoel
molting
PROTOSTOMES
mouth from blastopore
radial ancestry, two germ layers
DEUTEROSOMES
anus from blastopore
bilateral, coelomate ancestry, three germ layers
true tissues
multicelled body
Fig. 25-7, p.407

15. Deuterostomes
Protostomes
Fig. 25-2a, p.404

16. p.408

17. Choanoflagellates Protozoans most closely related to animals
Resemble collar cells (stay tuned for more on this)

18. flagellated collar cell
Animal Origins
flagellated collar cell
Fig. 25-4a, p.405

19. p.408

20. Sponges - Phylum Porifera
No symmetry, tissues or organs
Reproduce sexually
Microscopic swimming larvae

21. Sponge Structure water out glasslike structural elements amoeboid cell
pore
central cavity
semifluid matrix
flattened surface cells
water in
flagellum
microvilli
nucleus
Fig , p.409

22. Fig. 25-9a, p.408

23. Fig. 25-9b, p.408

24. Fig. 25-9c, p.408

25. p.408

26. Phylum Placozoa One living species, Tricoplax adherens
2-layer body, 3 mm across
Fig , p.409

27. p.408

28. Cnidarian Diversity Scyphozoans Anthozoans Hydrozoans Jellyfish
Sea anemones
Corals
Hydrozoans

29. Phylum Cnidaria Nerve net Hydrostatic skeleton Saclike gut nematocysts
capsule’s lid at free surface of epidermal cell
trigger
barbed thread inside capsule
nematocyst
Fig , p.410

30. mesoglea-filled bell
tentacles
Fig b, p.410

31. outer epithelium (epidermis) inner epithelium (gastrodermis)
Two Main Body Plans
Polyp
outer epithelium (epidermis)
mesoglea
(matrix)
Medusa
inner epithelium (gastrodermis)
Fig , p.410

32. Fig a1, p.411

33. Fig a2, p.411

34. Fig b, p.411

35. Fig a, p.431

36. Obelia Life Cycle (Hydrozoan)
female medusa
male medusa
reproductive
polyp
sperm
ovum
feeding polyp
zygote
polyp forming
planula
Fig a, p.411

37. Deuterostomes
Protostomes

38. Flatworms: Phylum Platyhelminthes
Acoelomate, bilateral, cephalized
Most hermaphroditic

39. Three Classes Turbellarians (Turbellaria) Flukes (Trematoda)
Tapeworms (Cestoda)

40. Planarian Organ Systems Digestive
branching gut
pharynx; protrudes onto food, then retracts into the body between feedings

41. Planarian Organ Systems Neuro-sensory
rudimentary brain (pair of large ganglia in head)
pair of nerve cords that have lateral branchings

42. Planarian Organ Systems Reproductive
ovary
testis
oviduct
genital pore

43. Planarian Organ Systems Excretory
pair of highly branched tubules that adjust water and solute levels in body
Fig d, p.412

44. flame cell
opening of tubule at body surface
Fig e, p.412

45. flame cell nucleus cilia fluid filters through membrane folds
Fig f, p.412

46. Fig , p.413

47. Fig. 25-18, p.413 proglottids scolex
a Larvae, each with inverted scolex of future tapeworm, become encysted in intermediate host tissues (e.g., skeletal muscle)
b A human, a definitive host, eats infected, undercooked beef which is mainly skeletal muscle
d Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts
c Each sexually mature proglottid has female and male organs. Ripe proglottids containing fertilized eggs leave host in feces, which may contaminate water and vegetation.
Fig , p.413

48. proglottids
scolex
Fig e, p.413

49. Deuterostomes
Protostomes

50. Rotifers
Bilateral
Cephalized
Crown of cilia at head
Complete gut

51. Fig a, p.416

52. one of two ciliated lobes at head end
mouth
modified pharynx; internal jawlike elements, salivary glands
cluster of nerve cells
gastric gland (esophagus behind it)
proto-nephridium
stomach
intestine
cloaca (this type is a chamber for digestive and excretory wastes)
anus
gland that secretes cementing substance for “toe”
one of two “toes”
Fig b, p.416

53. Two Coelomate Lineages
Protostomes
Mollusks
Annelids
Arthropods
Deuterostomes
Echinoderms
Chordates

54. Cleavage Patterns Protostome embryo (spiral cleavage)
Deuterostome embryo
(radial cleavage)

55. Deuterostomes
Protostomes

56. Annelids: Phylum Annelida
Segmented, coelomate worms
Class Polychaeta
Class Oligochaeta
Class Hirudinea

57. Polychaetes Most marine Bristles extend from parapods on each segment
“jaws”
toothlike structures
Most marine
Bristles extend from parapods on each segment
Head end is specialized
pharynx (everted)
antenna
palp
(food handling)
tentacle
eyes
chemical-sensing pit
parapod

58. Polychaetes
Fig a, p.414

59. Fig b, p.414

60. Fig c, p.414

61. Leeches - Class Hirudinea
Predators and parasites
Less obvious segmentation

62. before feeding
Fig a, p.414

63. after feeding
Fig b, p.414

64. Earthworm - An Oligochaete
No parapodia, few bristles per segment
Nerve cord
Dorsal blood vessel
Circular muscle
Coelom
Longitudinal muscle
Nephridium
Seta (retracted)
Nerve cord
Fig , p.415

65. Earthworm Nephridium bladderlike storage region of nephridium
nephridium’s thin loop reabsorbs some solutes, relinquishes them to blood
blood vessels
body wall
funnel (coelomic fluid with waste enters here)
external pore (fluid containing wastes discharged here)
Fig , p.415

66. Earthworm Circulatory System
Hearts
Fig , p.415

67. Earthworm Digestive System
Coelomic chambers
Crop
Gizzard
Esophagus
Pharynx
Mouth
Fig , p.415

68. Earthworm Nervous System
Brain
Nerve cord
Fig , p.415

69. head end
Fig g, p.415

70. of outwardly similar body segments are bristles used in locomotion
on both sides
of outwardly similar body
segments are
bristles used
in locomotion
Fig h, p.415

71. Old Genes, New Drugs
Fig. 25-1, p.402

72. Old Genes, New Drugs
p.403