1. Phylum Platyhelminthes & Nematoda

2. Platyhelminthes
Flatworms

3. 3 Classes Turbellaria Trematoda Cestoda Free-living, most marine,
flatworms
Trematoda
Parasitic, internal and external parasites,
flukes
Cestoda
Parasitic, live in intestine of humans and other animals, long & ribbon-like,
tapeworms

4. Characteristics Acoelomates – no true cavity Simplest animals with
bilateral symmetry
No specialized circulatory or respiratory system
(uses diffusion to transport oxygen and nutrients)
Excretes by diffusion

5. Characteristics Continue
Cephalization (sense organs and nerve cells gathered into a head region)
Primitive organ systems with true organs (digestion, excretion, reproduction)
Sexual and asexual reproduction
Hermaphroditic (both sexes) but do not self fertilize

6. Free-Living Flatworms (Aquatic) eg. Planaria

7. Planaria

8. Planaria – Class Turbellaria
Both marine and freshwater
Most are small (less then cm and few mm thick)
Primitive nervous systems allows for coordination of body movements
Simple eyes that detect light changes
(responds to stimuli!)

9. Feeding
Planaria have a gastrovacular cavity with 1 opening at end of muscular tube called a pharynx
Pharynx is protrusible (can extend)
Food is sucked into intestine via pharynx where enzymes digest food
Nutrients diffuse to rest of cells in body
Undigested material is ejested (spit out) via pharynx

10. Planarian Anatomy

11. Respiration Internal Transport
Exchange of gases (oxygen/carbon dioxide) diffuse through body wall
Internal Transport
Gastrovascular cavity distributes products of digestion throughout body tissues via diffusion

12. Excretion Response Flame cells – expel water
Metabolic waste removed by diffusion through body wall
Response
Most primitive animal with central nervous system (CNS)
Sense organs
Ocelli – eye spots sensitive to light
Tactile and chemoreceptors on auricles (“ears”)

13. Movement Cilia on epidermal cells help it to glide through the water
Mucus
Does not swim freely = glides
Muscles cells controlled by CNS
Allows for reaction to environment
Muscle fibers: longitudinally, circular and diagonally
Allows the flatworm to twist and turn

14. Planaria Movement Video Clip

15. Reproduction Two types of reproduction Asexual reproduction
Fission: constricting behind the pharynx and separates into 2 animals, each which regenerate the missing parts
A planaria is cut in two and regenerates into 2 whole organisms
Sexual reproduction
Worms come together and join up, exchanging sperm & eggs
Both sex organs on each worm (hermaphrodites) allow for cross fertilization of each worm

16. Planaria Regeneration Video

17. Flukes – Class Trematoda
Parasitic
Internal and External parasites
Lifecycle usually involves 2 or more different host
Animal intermediate host
Human final (definitive) host
Examples:
Blood Fluke – Schistosoma mansoni
Intermediate host is snails and definitive host is humans
Liver Fluke
Lung Fluke

18. Schistosoma mansoni Life cycle: Swimming larvae Burrow into snail
Reproduce asexually
Break out of snail
Swim in water
Bores through skin of human to blood vessels and then intestines
Blood vessels leak eggs into intestines
Very sick human

19. Tapeworms – Class Cestoda
Found inside and outside hosts
If inside cannot afford to grow too large or it will kill its host
Some can reach up to 30 m in length (found in a sperm whale)
Human tapeworms can be 7m
Lack : sensory organs, coordination for mobility, digestive system
Live in intestines - Feed on blood, tissue, fluids and pieces of cells

20. Tapeworms Continued
Highly developed reproductive system capable of producing hundreds and thousands of egg and sperm.
No digestive tract – absorb food as it passed by
Attaches to host
via suckers and
hooks

21. Tapeworms Continued
Have developed a way to maximize absorption of nutrients from their host by being flat and VERY long which increases their surface area to maximize the absorption of nutrients

22. Tapeworm Scolex

23. TAPEWORMS –Class Cestoda
Scolex
Proglottids (sections) form at anterior end

24. Tapeworm life cycle
Mature proglottids break off posterior
Eggs are released
Animal eats contamination
Forms a dormant cyst
Human eats
Hatch in host

25. Nematoda
Roundworms

26. Key Characteristics
Pseudocoelomate – fluid filled space between mesoderm and internal organs
Bilateral symmetry
Cephalization
Most simplest animals to have mouth, anus and complete digestive tract
3 tissue layers: ectoderm, mesoderm & endoderm
Body covered with a flexible nonliving cuticle secreted by ectoderm

27. Digestive System Tube shaped gut
Food ingested, nutrients absorbed via diffusion, waste removed through anus
Many are carnivorous, some are herbivores
Some attach to the roots of plants and suck out the plant juices
This can cause serious damage to plants and crops

28. Respiration Internal Transport
Exchange of gases (oxygen/carbon dioxide) diffuse through body wall
Internal Transport
None

29. Excretion Nervous System
Metabolic wastes (Carbon dioxide) leave by diffusion through body wall
Nervous System
Ganglia concentrated in head region – cephalization
has a dorsal nerve cord and lateral nerve cord
Nerves coordinate, transmit & control muscle movement and sensory input

30. Muscular System Reproduction Muscles run longitudinally
Can bend either dorsally or ventrally
Reproduction
Most are either male or female
Some are hermaphroditic

31. Parasitic Roundworms Complex lifecycles involving more than one host
Whole lifecycle can occur in a single host
Ex: Ascaris in human.

32. Trichonosis – 2 hosts