1. Invertebrate Diversity
Chapter 23
Invertebrate Diversity

2. 23.4 Flatworms, Mollusks, Annelids
A. Body Plan of Flatworms:
solid body with an incomplete or absent gut; flat
B. Form & Function in Flatworms:
1. Feeding: gastrovascular cavity with a tube called a pharynx; intestines branch in body; undigested food out through mouth
2. Respiration: diffusion

3. 23.4 Flatworms, Mollusks, Annelids
B. Form & Function in Flatworms:
3. Internal Transport: none
4. Excretion: diffusion
5. Response: simple brain and nerves; eyespots sense light; sensors for food
6. Movement: cilia to glide through water and muscles to twist and turn

4. 23.4 Flatworms, Mollusks, Annelids
B. Form & Function in Flatworms:
7. Reproduction: sexual or asexual; hermaphrodites; regeneration
8. Habitat: fresh and salt water, land
9. Examples: Planarians

5. Planarian

6. Planarian

7. Marine Flatworms

15. 23.4 Flatworms, Mollusks, Annelids
B. Form & Function in Parasitic Flatworms:
1. Feeding: some have a pharynx; others absorb food
2. Respiration: diffusion
3. Internal Transport: none
4. Excretion: diffusion
5. Response: not much
6. Movement: cilia, ?

16. 23.4 Flatworms, Mollusks, Annelids
B. Form & Function in Parasitic Flatworms:
7. Reproduction: complicated, sexual life cycles
8. Habitat: in host
9. Examples: flukes, tapeworms; have suckers on head and attach to intestines; uncooked meat

17. 23.4 Flatworms, Mollusks, Annelids
C. What are mollusks?
soft-bodied animals that have an internal or external shell
D. Body Plan of Mollusks:
1. foot: muscular; usually contains the mouth

18. Snail Foot

19. Octopus Foot

20. Clam Foot

21. 23.4 Flatworms, Mollusks, Annelids
D. Body Plan of Mollusks:
2. mantle: thin tissue layer that covers most of body
3. shell: made of CaCO3
4. visceral mass: beneath mantle, contains internal organs

22. Mollusk Comparison

23. 23.4 Flatworms, Mollusks, Annelids
E. Form & Function in Mollusks:
1. Feeding
a. complete digestive tract: food enters mouth, digested in gut, absorbed, waste out anus
b. radula: used to scrape plants (snails, slugs)
c. gills: used to filter feed (bivalves)

24. Radula

25. Radula

26. 23.4 Flatworms, Mollusks, Annelids
E. Form & Function in Mollusks:
2. Respiration
a. gills
b. moist mantle cavity (land snails)
3. Internal Transport
a. open circulatory system: blood flows in cavities (snails and slugs)
b. closed circulatory system: blood flows in vessels (octopi and squids)

27. 23.4 Flatworms, Mollusks, Annelids
E. Form & Function in Mollusks:
4. Excretion
a. nephridia: remove ammonia from blood
5. Response
a. simple: clam—nerves, chemical and touch receptors, eyespots
b. complex: octopus—well-developed brain capable of memory and learning

28. 23.4 Flatworms, Mollusks, Annelids
E. Form & Function in Mollusks:
6. Movement: crawling, swimming, jet propulsion
7. Reproduction
a. separate sexes and external fertilization (snails and bivalves)
b. internal fertilization (tentacled mollusks and certain snails)

29. 23.4 Flatworms, Mollusks, Annelids
F. Mollusk Classes
1. Gastropods: Snails and Slugs
a. gastropod: “stomach foot”
b. one-piece shell (except slugs)
c. use hiding, swimming, or poison for protection

30. Sea Slug

32. Banana Slug

33. Giant Land Snails

34. 23.4 Flatworms, Mollusks, Annelids
F. Mollusk Classes
2. Bivalves: Two-Shelled Mollusks
a. bivalve: “two shell”
b. shells hinged at back
c. Examples: clams, oysters, and scallops
d. usually sessile

38. 23.4 Flatworms, Mollusks, Annelids
F. Mollusk Classes
3. Cephalopods: Tentacled Mollusks
a. cephalopod: “head foot”
b. Examples: octopi, squids, nautiluses
c. usually have 8 tentacles with suckers for grabbing prey

39. 23.4 Flatworms, Mollusks, Annelids
F. Mollusk Classes
3. Cephalopods: Tentacled Mollusks
d. swim or squirt ink for protection; octopi can change color to match surroundings

45. 23.4 Flatworms, Mollusks, Annelids
G. What are annelids?
round, wormlike animal that has a long, segmented body

47. 23.4 Flatworms, Mollusks, Annelids
H. Form & Function in Annelids:
1. Feeding
a. complete digestive tract
b. eat waste; some are filter feeders
2. Respiration
a. gills
b. moist skin
3. Internal Transport
a. closed circulatory system w/ multiple hearts

49. 23.4 Flatworms, Mollusks, Annelids
H. Form & Function in Annelids:
4. Excretion
a. nephridia
5. Response:
a. brain and nerves
b. sensory tentacles, chemical receptors, eyes
c. Protection: poisons, burrows, swimming, biting

51. Tube Worm

52. 23.4 Flatworms, Mollusks, Annelids
H. Form & Function in Annelids:
6. Movement
a. longitudinal muscles: cause the worm to shorten
b. circular muscles: make the worm skinnier
c. hydrostatic skeleton

53. 23.4 Flatworms, Mollusks, Annelids
H. Form & Function in Annelids:
7. Reproduction
a. sexual or asexual
b. some separate sexes and external fertilization
c. some hermaphrodites and internal fertilization (earthworms)

54. Osedax on Whale Bone