1. Flatworms and Annelids

2. Levels of Organization
Levels of Organization
All animals are multicellular – made of more than 1 cell
Animals can be organized on the cellular, tissue, or organ level of organization.
Cell – Sponge
Tissue – Jellyfish
- Have endoderm & ectoderm only
Organ – Worms
- Have ectoderm, endoderm, and mesoderm

3. Type of Body Plan Two body plans are present in the animal kingdom:
Sac plan:
Incomplete digestive system with only one opening.
Ex: Jellyfish
& planaria

4. Tube-within-a-tube plan:
Complete digestive system.
Two openings allows for specialization along the length of the tube.
Ex: Roundworms, earthworms, insects

5. Type of Symmetry Three types:
Type of Symmetry
Three types:
Asymmetrical animals have no particular symmetry.
Radial symmetry means the animal is organized similar to a wheel.
Bilateral symmetry means the animal has definite right and left halves.

8. Type of Coelom
Coelom - an internal body cavity where internal organs are found.
Ex: Mollusks, annelids, echinoderms, vertebrates
Pseudocoelom - a body cavity incompletely lined with mesoderm.
Ex: Roundworms, rotifers
Acoelomates - have mesoderm but no body cavity.
Ex: Flatworms, sponges, jellyfish

10. Segmentation
Segmentation is the repetition of body parts along the length of the body.
Animals can be segmented or nonsegmented.
Segmentation leads to specialization of parts.
Ex: annelids, arthropods, and chordates (includes vertebrates).

11. Phylum Platyhelminthes
Meaning – flatworms
Symmetry - bilateral
Sac body plan
Non-segmented
Acoelomates
Organization – organ level
Have organs for all life processes except respiration and circulation
Habitat – fresh or salt water, moist environments, inside host

12. Examples:
Tapeworms
Flukes
Marine flatworms
Freshwater planarians

13. Planarians - Lifestyle - free-living Habitat - freshwater
Movement – secrete slime, push through with cilia, muscles
Excretion – flame cells – interconnecting canals throughout body
Response - small brain
- ladder of nerves
- light-sensitive eyespots
- Auricles sensitive to chemicals
Respiration - diffusion

14. Internal transport - diffusion
Diet – plankton (small worms or crustaceans)
Feeding – wrap around prey
- secrete slime
- extend pharynx to suck up food
Digestion – occurs in GVC
Gender - hermaphrodites
Sexual reproduction – have sex, exchange sperm, each planaria gets pregnant - 2 sets of young hatch from eggs 2-3 weeks later.

15. Asexual reproduction – capable of regeneration; 1 worm can even grow 2 heads or 2 tails!!

16. Planarian

17. Eyespot Brain Auricle GVC Pharynx Mouth Mesoderm Endoderm Ectoderm GVC
Longitudinal
nerve cord
GVC
Transverse
nerve cord
Pharynx
Mouth
Mesoderm
Endoderm
Ectoderm
GVC
Flame
cells
Cilia
Flame
cells
Excretory pore

18. Parasitic Flatworms Tapeworm – Two classes - flukes and tapeworms
Require host to carry on life cycle – see next slide
Primary host – infect as adult
Secondary host – infect as larval stage
Tapeworm –
Scolex with hooks and suckers to hold itself inside the gut.
No digestive system; absorbs host’s digested food through skin

19. Body is an assembly line of square sections called proglottids, which contain male and female sex organs.
As proglottids mature, they break off, pass with feces, and release eggs.
When animals feed in feces-contaminated food, larva eventually form cysts in muscles of secondary host.
When humans eat infected meat, larva hatch from cyst, attach to intestine, and grow to adulthood.

20. Hooks
Suckers
Scolex
Neck
Proglottids
Testes
Ovary
Eggs
Detached proglottid
Longitudinal nerve cord
Brain (ganglia)
Transverse nerve cord

21. Life cycle:

22. Contracted by eating undercooked, infected beef, pork, or fish.
Transmitted to cats & dogs by fleas that have eaten feces of infected host
Primary symptom – weight loss
In prolonged infections – worms migrate to eyes, heart, brain, lungs, & liver & form cysts – cause swelling, cramps, diarrhea, anemia, & seizures
Diagnosed by fecal exam; treated with medicine

23. Fluke Have sucker at anterior end to attach to host
Various species – can infect digestive tract, bile duct, blood, & lungs.
Blood flukes cause schistosomiasis – one of the most common worm infections worldwide (about 200 million in mostly Middle East, Asia, Africa, & S. America)
Common in areas with poor sewage treatment
Enter through skin when in infected water – see life cycle diagram next slide

24. Schistosomiasis

25. Diagosed by fecal exam; treated with medicine
Symptoms: nausea, abdominal pain, increased bowel movements, diarrhea, weight loss, fatigue
Burrow through host, feed on host’s blood & tissues.
Can live for up to 2-3 decades inside host (usually only 5-10 years)
Reproduce non-stop – 100 – 300 eggs/day

26. Phylum Annelida (segmented worms)
Symmetry - bilateral
Organization - 3 germ layers – organ level
Coelomates -have a body cavity – more complex organs
Segmented
Habitat – fresh or salt water, soil
Tube-within-a-tube body plan – specialized organs in digestive tract (see earthworm later)

27. Support - hydrostatic skeleton (fluid-filled chambers in body).
Respiration - breathe through their skin - diffusion.
Internal transport - closed circulatory system with 5 aortic arches (hearts) and blood vessels that run the length of the body and branch to every segment.
Excretion –
Nephridia (tiny tubes found in each segment) remove nitrogen waste through openings in body wall
Anus removes waste from digested food.

28. Movement - alternating contraction of longitudinal and circular muscles found in each segment.
Response - brain connected to a ventral nerve cord .
Three classes –
Polychaeta – marine worms
Oligochaeta – earthworms
Hirudinea - leeches

29. Earthworm, Lumbricus

31. Mouth
Pharynx
Esophagus
Crop
Gizzard
Intestine
Anus
Aortic arches (hearts)
Dorsal blood vessel
Ventral blood vessel
Brain
Ventral nerve cord
Clitellum
Setae

32. Clitellum
Testis
Sperm reservoir
Seminal
receptacle
Ovary

33. Excretory pore
Tubule
Nephridium

34. Intestine
Coelom
Muscle
Epidermis
L1. Cuticle
M1. Blood vessel
M2. Blood vessel
N. Nerve cord
O. Nephridium
P. Setae

35. Earthworms
Have pairs of setae in each segment; when muscles contract in each segment, setae anchor in the soil, and aid locomotion.
Diet - leaves & decaying matter
Digestion: Mouth  Pharynx (swallows food)  Esophagus (connects pharynx & crop)  Crop (stores food)  Gizzard (grinds food – contains small stones swallowed by the worm)  Intestine (digests food)

36. Gender - hermaphroditic.
Reproduction
Meet at clitellum (smooth part of worm), which secretes a ring of mucus
Each injects sperm into mucus
Tube slides forward, picking up eggs
Tube slides off body & is left behind
Fertilization occurs within tube
Worms hatch in a few weeks – no larval stage
Two sets of young

38. Leeches
Most in fresh water, some in soil or salt water.
2 suckers (1 small anterior, 1 large posterior) to feed.
Some are free-living predators; most are fluid feeders that attach themselves to open wounds.
Bloodsuckers cut through tissue with 3 saw-like jaws – leaves “Y” – shaped wound.
Anesthetic in saliva prevents victim from feeling attack and dilates blood vessels; anticoagulant (hirudin) in their saliva keeps blood from clotting; pouches in crop allows for storage of up to 5 times their weight – long time between feedings.