3. Three Classes of Flatworms (Phylum Platyhelminthes)
1. Class Turbellaria (planaira)
2. Class Trematoda (flukes)
3. Class Cestoda (tapeworms)

4. Kingdom Animalia Phylum Platyhelminthes
Flatworms are on the acoelomate branch of the evolutionary tree
Acoelomates—no respiratory or circulatory systems

5. Body Structure of Flatworms
Chapter 25
Worms and Mollusks
25.1 Flatworms
Body Structure of Flatworms
Bilateral symmetry
Thin, flat bodies
Cephilization: Definite head region and body organs

6. Feeding and Digestion
Free-living flatworms feed on dead or slow moving organisms
Parasitic flatworms have modified feeding structures called hooks and suckers
Enables them to stay attached to host

7. Respiration, Circulation, Excretion
Chapter 25
Worms and Mollusks
25.1 Flatworms
Respiration, Circulation, Excretion
Diffusion moves dissolved oxygen and nutrients to all parts of their bodies.
Carbon dioxide and other waste is removed by diffusion.

8. Chapter 25
Worms and Mollusks
25.1 Flatworms
Flame cells move water out of the body to excrete waste products and maintain water balance.

9. The nervous system regulates the body’s response to stimuli.
Chapter 25
Worms and Mollusks
Response to Stimuli
The nervous system regulates the body’s response to stimuli.
Cephalization

10. Move by contracting muscles in the body wall
Chapter 25
Worms and Mollusks
25.1 Flatworms
Movement
Move by contracting muscles in the body wall
Glide by using cilia located on their undersides

11. Flatworms are hermaphrodites
Chapter 25
Worms and Mollusks
25.1 Flatworms
Reproduction
Flatworms are hermaphrodites
Two different flatworms exchange sperm, and the eggs are fertilized internally

12. Chapter 25
Worms and Mollusks
25.1 Flatworms
Free-living flatworms can reproduce asexually by regeneration or fragmentation

13. Turbellarians (planaria)
Chapter 25
Worms and Mollusks
25.1 Flatworms
Turbellarians (planaria)
Live in marine or freshwater
Have eyespots that can detect the presence or absence of light
Carnivores or scavengers

14. Parasites that infect the blood or body organs of their hosts
Chapter 25
Worms and Mollusks
25.1 Flatworms
Trematodes (flukes)
Parasites that infect the blood or body organs of their hosts
The parasitic fluke Schistosoma makes people sick with dysentery or swimmer’s itch
These fluke eggs clog blood vessels, causing swelling and eventual tissue damage.

15. Genus Shistosoma

16. Chapter 25
Worms and Mollusks
25.1 Flatworms

17. Parasites adapted to life in the intestines of their hosts
Chapter 25
Worms and Mollusks
25.1 Flatworms
Cestodes (tapeworms)
Parasites adapted to life in the intestines of their hosts
No mouth or gut: absorb digested material from the host
No nervous system

18. Structure:
Scolex: “head” that attaches to the host’s intestine
Proglottis: body that contains male and female sex organs

20. Phylum Nematoda

21. Kingdom Animalia Phylum Nematoda
Body structure of Roundworms :

22. Feeding and Digestion Simplest animal with a digestive tract (one way)
Most are free living, some are parasitic

23. Respiration and Circulation: Diffusion through their moist skin
Chapter 25
Worms and Mollusks
25.2 Roundworms
Respiration and Circulation: Diffusion through their moist skin
Response to Stimuli: Ganglia and a nerve cord
Movement: Muscles cause their bodies to move in a thrashing matter

24. Roundworms reproduce sexually.
Chapter 25
Worms and Mollusks
25.2 Roundworms and Rotifers
Reproduction
Roundworms reproduce sexually.
Fertilization is internal.
Larva hatch from the fertilized eggs.

25. Diversity of Roundworms
Chapter 25
Worms and Mollusks
25.2 Roundworms and Rotifers
Diversity of Roundworms
Trichinella worms
Hookworms
Ascarid worms
Pinworms
Filarial worms

26. Hookworm

27. Trichinella

28. STOP

29. Body Structure of Mollusks
Chapter 25
Worms and Mollusks
25.3 Mollusks
Body Structure of Mollusks
Mollusks are coelomate animals with bilateral symmetry, a soft internal body, a digestive tract with two openings, a muscular foot, and a mantle.

30. Mantle: membrane that surrounds the internal organs
Secretes calcium carbonate to form shells

31. Chapter 25
Worms and Mollusks
25.3 Mollusks

32. A radula scrapes food into their mouths.
Chapter 25
Worms and Mollusks
25.3 Mollusks
Feeding and Digestion
A radula scrapes food into their mouths.
Radula: tongue-like organ with teeth

33. Chapter 25
Worms and Mollusks
25.3 Mollusks
Mollusks have complete guts with digestive glands, stomachs, and intestines.

34. Gills are parts of the mantle.
Chapter 25
Worms and Mollusks
25.3 Mollusks
Respiration
Gills are parts of the mantle.
Gills contain blood for the transport of oxygen to the tissue and for the removal of carbon dioxide from the tissue/blood.

35. is pumped out of vessels into open spaces surrounding the body organs.
Chapter 25
Worms and Mollusks
25.3 Mollusks
Circulation
is pumped out of vessels into open spaces
surrounding the body organs.
In an open circulatory system, blood
Oxygen and nutrients diffuse into tissues that are bathed in blood and carbon dioxide diffuses from tissues into the blood.

36. In a closed circulatory system, blood is confined to
Chapter 25
Worms and Mollusks
25.3 Mollusks
In a closed circulatory system, blood is confined to
vessels as it moves through the body
Ex. squid

37. Chapter 25
Worms and Mollusks
25.3 Mollusks
Excretion
Mollusks get rid of metabolic wastes from cellular processes through structures called nephridia.
Nephridia: organ that allows for homeostatis by filtering the blood and removing waste

38. Response to Stimuli
Nervous systems coordinate their movements and behavior.

39. Chapter 25
Worms and Mollusks

40. Mollusks reproduce sexually.
Chapter 25
Worms and Mollusks
25.3 Mollusks
Reproduction
Mollusks reproduce sexually.
All mollusks share similar developmental patterns.

41. The largest class of mollusks is Gastropoda.
Chapter 25
Worms and Mollusks
25.3 Mollusks
Diversity of Mollusks
Gastropods
The largest class of mollusks is Gastropoda.
Most species of gastropods have a single shell.
Ex. Snails and conches
Slugs do not have shells.

42. Gastropods

43. Bivalves are two-shelled mollusks.
Chapter 25
Worms and Mollusks
25.3 Mollusks
Bivalves
Bivalves are two-shelled mollusks.
Ex. Clams, mussels, oysters, and scallops
Use a muscular foot to burrow into wet sand

44. Bivalves

45. Cephalopods 25.3 Mollusks Ex. Squid, octopus, chambered nautilus
Chapter 25
Worms and Mollusks
25.3 Mollusks
Cephalopods
Ex. Squid, octopus, chambered nautilus
The foot of a cephalopod is divided into arms and tentacles with suckers.
Cuttlefish

46. Cephalopod Protection
Chapter 25
Worms and Mollusks
25.3 Mollusks
Cephalopod Protection
Expel water to propel themselves away from threat
Hide
Shoot out an inky substance that forms a cloud
Change color to blend in with their surroundings

47. Annelids-Segmented Worms

48. Body Structure of Segmented Worms
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Body Structure of Segmented Worms
Include earthworms, marine worms, and parasitic leeches
Segmented and have a coelom

49. Annelids: Segmented Worms

50. Hydrostatic skeleton that muscles can push against
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Movement
Hydrostatic skeleton that muscles can push against
The earthworm contracts circular muscles running around each segment.
This squeezes the segment and causes the fluid in the coelom to press outward like paste.

51. Chapter 25
Worms and Mollusks
25.4 Segmented Worms
The earthworm contracts the longitudinal muscles that run the length of its body.
This causes the segment to shorten and return to its original shape, pulling its posterior end forward and resulting in movement.

52. Setae: 4 pairs of bristles, found on each segment, used with digging
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Segmentation permits segments to move independently of each other and enables a worm to survive damage
Setae: 4 pairs of bristles, found on each segment, used with digging

53. Setae

54. Feeding, Digestion, Excretion
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Feeding, Digestion, Excretion
Digestive tract runs through all segments

55. Mouth: pharynx that sucks up food
Esophagus: carries food to the crop
Crop: stores food
Gizzard: grinds organic debris using sand

57. Segmented worms have an intestine
Have an anus
Have two nephridia in almost every segment

59. Chapter 25
Worms and Mollusks

60. Most annelids have a closed circulatory system.
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Circulation
Most annelids have a closed circulatory system.

61. No true heart— 5 pairs of muscular tubes that pump blood

63. Aquatic annelids have gills for the exchange of gases in the water.
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Respiration
Diffusion: Earthworms take in oxygen and give off carbon dioxide through their moist skin.
Aquatic annelids have gills for the exchange of gases in the water.

64. Response to Stimuli Brain and nerve cord 25.4 Segmented Worms
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Response to Stimuli
Brain and nerve cord

65. Reproduction (hermaphrodites)
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Reproduction (hermaphrodites)
Reproduce both sexually and asexually
Sperm are passed between two worms near segments called the clitellum.

66. Clitellum: secretes a ring of mucus into which eggs and sperm are released
Ring slides off worm’s body and forms a cocoon for eggs

67. Diversity of Annelids--subclasses
Chapter 25
Worms and Mollusks
25.4 Segmented Worms
Diversity of Annelids--subclasses
Earthworms: Oligochaeta

68. Marine annelids: Polychaeta

69. Leeches: Hirudinea