1. PHYLUM PLATYHELMINTHES (“FLAT WORMS!”)
Hello!
PHYLUM PLATYHELMINTHES (“FLAT WORMS!”)
Diana Luo
Hong Joo Kim
Carrie Yang
Period 5

2. CLASSES OF FLATWORMS (TURBELLARIA)
Most are marine organisms, some are freshwater
All are free-living organisms
Feeds on smaller animals, dead animals
Dugesia “planarians” (about 4,500 species)
Diana Luo, Hong Joo Kim, Carrie Yang

3. CLASSES OF FLATWORMS (MONOGENEA)
Marine and freshwater parasites
Most are external parasites of fish
Relatively simple life cycle
Monogeneans (about 1,100 species)
Diana Luo, Hong Joo Kim, Carrie Yang

4. CLASSES OF FLATWORMS (TREMATODA)
Suckers for attaching to internal organs or outer surfaces of the host
Many require an intermediate host in which larvae develop
Trematodes, flukes (about 11,000 species)
Diana Luo, Hong Joo Kim, Carrie Yang

5. CLASSES OF FLATWORMS (CESTODA)
Live mostly inside vertebrates & are parasites
Flat, slender, long bodies
Scolex – suckers + hooks
Tapeworms (3,400 species)
Diana Luo, Hong Joo Kim, Carrie Yang

6. BODY SYMMETRY…& BODY CAVITY?
BILATERAL symmetry (identical shape on either side)
Unlike other bilaterians, flatworms do NOT have body cavity between the digestive cavity and outer body wall.
Diana Luo, Hong Joo Kim, Carrie Yang

7. NERVOUS SYSTEM
Flatworms have a Central Nervous System (CNS) – the brain and the ventral nerve cords
A pair of ganglia is located at the anterior end
Diana Luo, Hong Joo Kim, Carrie Yang

8. SENSORY STRUCTURES/FEATURES
Ganglia, or clusters of neurons, present at the anterior end  demonstrates cephalization, trend in which nervous tissue becomes concentrated at one end
A planarian’s head is equipped with a pair of light-sensitive eyespots and lateral flaps that function mainly to detect specific chemicals.
Diana Luo, Hong Joo Kim, Carrie Yang

9. CIRCULATORY SYSTEM They have no organs specialized for circulation
A muscular pharynx that leads to the digestive system is present instead
Diana Luo, Hong Joo Kim, Carrie Yang

10. DIGESTIVE SYSTEM
They have a gastrovascular cavity with only one opening. The many branches of this distribute food throughout the animal
Diana Luo, Hong Joo Kim, Carrie Yang

11. EXCRETORY SYSTEM
They have a excretory system that eliminates nitrogenous waste (ammonia) by diffusion across the body surface.
Simple excretory apparatus (which consists of ciliated cells called flame bulbs that waft fluid through branched ducts opening to the outside) functions to maintain osmotic balance with their surroundings
Diana Luo, Hong Joo Kim, Carrie Yang

12. LOCOMOTION/MUSCULATURE
Glide along surfaces on mucus that they secrete
Others use muscles to swim through water with an undulating motion
Planarians move by using cilia on their ventral epidermis
Diana Luo, Hong Joo Kim, Carrie Yang

13. SKELETAL TYPE
The interstitial fluid acts as a hydrostatic skeleton – flatworms change the shapes of the fluid-filled compartments to control their overall form and movement
Diana Luo, Hong Joo Kim, Carrie Yang

14. REPRODUCTION (METHODS, TYPES)
Triploblastic development (ectoderm, mesoderm, endoderm)
Planarians can reproduce asexually (through regeneration) or sexually
Tapeworms have proglottids that produce thousands of eggs
Copulating mates cross- fertilize
Diana Luo, Hong Joo Kim, Carrie Yang

15. GAS EXCHANGE (HOW, STRUCTURES)
Flat shape places all the cells close to surrounding water  gas exchange by diffusion
No organs are specialized for gas exchange Every cell is able to partake in gas exchange
Diana Luo, Hong Joo Kim, Carrie Yang

16. Thank you
for listening!
A QUIZ??

17. QUIZ QUESTIONS
1. While of the following have bilateral symmetry? a. Porifera (Sponges) b. Cnidaria (Jellyfish and Anemones) c. Platyhelminthes (Flatworms) d. Nematoda (Roundworms)
2. What do Annelida (Segmented Worms) have that Platyhelminthes (Flatworms) do not have? a. Bilateral Symmetry b. Body Cavity c. Respiratory System d. Nervous System
Diana Luo, Hong Joo Kim, Carrie Yang

18. QUIZ QUESTIONS
3. What do all of the following have in common: Platyhelminthes (Flatworms), Arthropoda (Insects and Arachnids), Mollusca (Snails, Clams, and Squids), and Echinodermata (Sea Stars and Sea Urchins) a. Segmentation b. Open Circulatory System c. Asexual Reproduction d. Organ System
4. What is the main difference between Platyhelminthes (Flatworms) and Nematoda (Roundworms)? a. A respiratory system b. Symmetry c. Digestive System d. Segmentation
Diana Luo, Hong Joo Kim, Carrie Yang

19. QUIZ ANSWERS
1. C and D
Explanation: Porifera do not have symmetry and Cnidaria have radial symmetry.
2. B
Explanation: Both have bilateral symmetry and nervous systems (although their nervous systems slightly differ). Neither has a respiratory system.
3. D
Explanation: Only the Arthropoda have segmentation. Only Mollusca and Arthropoda have open circulatory systems. Mollusca and Arthropoda do not undergo asexual reproduction.
4. C
Explanation: Platyhelminthes have gastrovascular cavities while Nematoda have a separate mouth and anus. Neither have a respiratory system or segmentation. Both have bilateral symmetry.
Diana Luo, Hong Joo Kim, Carrie Yang

20. Thank you for listening!
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