2. Platyhelminthes General characteristics:
Known as “flat worms.”
Body plan: acoelomate, bilateral symmetry
Habitat: aquatic or in host’s body

3. Platyhelminthes Nutrition:
Parasitic - (blood, tissue, or predigested materials from host’s intestines) OR
Scavengers and Saprobes

4. Platyhelminthes Feeding: Planarians extend pharynx from mouth
Parasites have specialized mouth parts to attach to their host.

5. Platyhelminthes Digestion: Excretion: diffusion through the body wall
Extracellular: food is pumped into digestive cavity or gut and cells digest and absorb nutrients, digested food is then diffused into the other body tissue
Excretion: diffusion through the body wall
planarians have flame cells to excrete water and wastes through pores

6. Platyhelminthes
Respiration and Circulation: Diffusion of gases through the skin, skin must remain moist

7. Platyhelminthes
Nervous: most have ganglia (mass of nervous tissue), eyespots, sensory lobes and respond to touch and chemicals
Demostrates cephalization, nervous tissue is concentrated in the head region.

8. Platyhelminthes Reproduction: Sexual Reproduction: Hermaphrodites
Parasitic worms require hosts to reproduce
Sexual reproduction exchange sperm, internal fertilization

9. Schistosome Life Cycle
Section 27-1
Primary host (human)
Intermediate host (snail)
Flukes mature and reproduce sexually in the blood vessels of human intestines. Embryos are released and passed out with feces.
Adult
fluke
Human
intestine
Embryo
Ciliated
larva
Tailed
larva
After asexual reproduction, new larvae are released from the snail into the water. They then infect humans, the primary host, by boring through their skin.
Once in the water, embryos develop into swimming larvae that infect an intermediate host (snail).
Shistosomiasis

10. Tapeworm Life Cycle

11. DON’T DO THIS!! GROSS!

12. Platyhelminthes Reproduction:
Asexual reproduction through fragmentation or fission.

13. Platyhelminthes Mobility: Cilia for gliding
Muscle cells controlled by nervous system to react to stimuli

14. The Anatomy of a Flatworm
Eyespot
Ganglia
Freshwater flatworms have simple ganglia and nerve cords that run the length of the body. The excretory system consists of a network of tubules connected to flame cells that remove excess water and cell wastes.
Head
Nerve cords
Gastrovascular cavity
Flatworms use a pharynx to suck food into the gastrovascular cavity. Digested food diffuses from the cavity into other cells of the body. Eyespots in some species detect light.
Excretory system
Ovary
Testes
Mouth
Pharynx
Most flatworms are hermaphrodites, having male reproductive organs (testes) and female reproductive organs (ovaries) in the same organism.
Flame cell
Excretory tubule

15. Platyhelminthes Common Examples: Turbellaria (Planarian)
Trematoda (Fluke)
Cestoda (Tapeworm)

17. Nematoda General characteristics: Known as “round worms”.
Pseudocoleomate
long and slender, tapered at both
ends
protostomes
bilateral symmetry
Body is covered in a complex cuticle

18. Nematoda Habitat/Nutrition: Parasites Feeding
Both mouth and anus connected by digestive tube
Digestion: takes place in digestive cavity, digested food diffuses into other body tissue.
May also have digestive sacs that food is pumped into for digestion.

19. Nematoda

20. Nematoda
Circulation and Respiration: Diffusion of gases through the skin
Excretion: Canal system, diffusion through body wall or out through mouth
Nervous: simple nervous system, with a main ventral (belly) nerve cord and smaller dorsal (back) nerve cord

21. Nematoda Reproduction: Sexual usually dioescious (separate sexes)
internal fertilization
genders differ in size, shape and color
Parasitic worms require host

22. Life Cycle of Hookworm

23. Life Cycle of Whipworm

24. Nematoda
Mobility: Muscles along body wall for movement

25. Nematoda
Examples:
Hookworms
Pinworms
Guinea worms

27. Annelida General characteristics: Habitat: aquatic and moist soil
Known as “segmented worms”
Coelomates
Habitat: aquatic and moist
soil

28. Annelida
Nutrition: heterotrophic, filter feeders, parasites, scavengers, and saprobes
Feeding: Pharynx used to obtain food
Carnivorous species have two or more sharp jaws

30. Annelida Digestive wastes pass out through the anus
Excretion:
Digestive wastes pass out through the anus
Cellular wastes containing nitrogen is passed out by the nephridia (simple kidney)

31. Annelida Digestion: extracellular, takes place in intestine
Earthworm: pharynx → esophagus→ crop (storage) → gizzard (ground) → intestines (absorption)

32. Annelida
Circulation:
closed (blood contained in vessels)

33. Annelida Respiration: Aquatic: breathe through gills
Land dwellers: diffusion through skin (must stay moist) typically secrete a mucus to keep skin moist

34. Annelida
Nervous:
Best developed sense organs in free living marine organism
Well developed nervous systems consisting of brain and spinal cord
Two or more pairs of eyes, sensory tentacles, chemical receptors and statocysts that help detect gravity

35. Annelida Reproduction Most sexually
Some use external fertilization and have separate sexes
Earth worms and leeches are hermaphroditic, but rarely fertilize their own eggs

36. Annelida
Mobility
Two major groups of muscles that function as part of the hydrostatic skeleton
Longitudinal and circular muscles, move by alternating contractions
Earthworms have hair-like structures called setae that allow them to easily grip a surface.
Marine worms have parapodia to use for swimming and crawling

37. Section 27-3 Anus Setae Clitellum Circular muscle Longitudinal muscle
Nephridia
Ganglia
Ring vessels
Reproductive organs
Ventral blood vessel
Ganglion
Brain
Mouth
Dorsal blood vessel
Crop
Gizzard
Body segments
Setae

38. Annelida
Examples:
Earthworms
Leeches
Marine worms