1. Platyhelminthes Flat worms Bilateral symmetry
Exchange O2/CO2 through skin (diffusion)
No circulatory system
Incomplete digestive system (1 opening … gut)
Cephalized (sensory organs at “head”)
Pseudocoelemate…2 layers with fluid in between

2. Flat worms Many are parasites e.g. Planaria (Class Turbellaria)
Scavenge for food, taken in through pharynx
Water excreted through flame cells
Cerebral ganglia collection of nerves (“brain”)
Fission/sexual repro. (herm, exchange sperm)
Eye spots sense light
Flat worms

3. Flat worms e.g. Flukes (Class Trematoda)
Live blood, intestines, lungs, liver…
Suckers to attach, draw in body fluids
Hermaphroditic
Life cycle with more than 1 host
E.g. schistosomiasis

4. Schistosome Big one is female, little one is male Spread by snails!
Causes enlargement of liver/spleen

5. Schistosomiasis

7. Flat worms e.g. tapeworms (class Cestaoda)
live in intestines, absorb nutrients
Scolex (head) has hooks and suckers to attach
Produces eggs in proglottids (segments)

8. Tapeworm

11. Marine Flatworm

12. Marine Flatworm

13. Nematoda Round worms Bilateral symmetry
Pseudocoelemate…2 layers with fluid in between
Complete digestive system (2 openings)…specialized organs with specific functions
Seperate sexes
Many are parasites

14. Roundworms Ascaris Hookworms Trichinella Pinworms Filarial worms
Live in intestines block them
Hookworms
Live in intestinal wall, feed on blood anemia
Trichinella
Live in muscle pain, stiffness, death
Pinworms
Live in mesentaries of intestine, crawl out at night to lay eggs
Filarial worms
Live in lymph system
Elephantiasis
Heartworms

15. Ascaris Worms

19. Hookworms

20. Heartworm

21. Trichinella

25. Pinworm G

26. Pinworm

27. Filarial worms

29. Filarial Worms

30. Elephantiasis
Even once the worms are removed, it will stay like this the rest of their life
Often infects genitalia/anal
Often gets other infections that kill the person

31. Annelida “little rings”… segmented worms bilaterally symmetrical
complete digestive tract
true coelem … 2 layers, space between, allows body to expand/contract in parts
segments allow worm to survive when some parts are damaged

32. Segmented worms Earthworms
Moves via setae, and 2 sets of muscles (circular and longitudinal)
Squeeze circular muscle, and worm anterior moves forward, plants setae, squeeze longitudinal muscles to bring posterior up
Complete digestive system (mouth, pharynx, crop, gizzard, intestine, anus)
Closed circulatory system (blood moves posterior on dorsal side, anterior in ventral side)

33. Segmented worms
breathe through skin (why you see them on sidewalk when it rains)
ventral nerve cord and cerebral ganglia (“brain”)
nephridia (primitive kidney) in each segment
hermaphroditic, but exchange sperm to reproduce, then lay eggs
clitellum secretes mucus to hold them together

34. Earthworm

36. Leeches No setae…sucker at each end
Secrete an anesthetic, so you don’t feel them, and a anticoagulent to keep blood from clotting
Will fall off when “full,” otherwise pull them off (don’t cut or burn!)
Used for reattachment surgery!

37. Class Hirudinea

39. OK…to end to a peaceful note, these, too, are segmented worms…
OK…to end to a peaceful note, these, too, are segmented worms…. They’re marine worms called feather dusters…