Introduction to Nematoda (Roundworms) Biology 11 Mrs. Trevelyan

Nematoda 1. PRESCRIBED LEARNING OUTCOMES and VOCABULARY 2. VIDEOS: None  3. TEXTBOOK PGS Section 26.3 pgs 706-710

Overview…

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Examples of Members:

1. Unifying Characteristics Bilateral symmetry, no segmentation Some free living, most parasitic on animals (humans too!) Pseudocoelom (false coelom) Body “cavity” contains organs Has 2 openings- a separate mouth and anus Has a 1-way digestive tract Ends of body “taper” off No skeleton, circulatory or respiratory systems Sexual reproduction with separate male and female

2. Structure Cephalisation with tapered ends Has 3 cell layers and a pseudocoelom Development of more complex tissues and organs (e.g. mouth, pharynx, intestine, rectum, anus, etc)

3. Digestion two openings Free-living are carnivores Parasitic flatworms anchor themselves to their host and live off of host tissue/blood

4. Respiration/Excretion No Respiratory organs Exchange gases by diffusion EXCRETION Solid wastes exit the body through the anus liquid wastes exit the body through excretory pore

5. Nervous System More advanced than flatworms Have a ring of nerve tissue around the pharynx Has 2 nerve cords (dorsal and ventral) Some sensory projections on head

6. Reproduction Roundworms usually have separate male and female Reproduce sexually Internal fertilization, female keeps fertilized eggs in uterus until laid Some species, like Ascaris, can lay 200, 000 eggs a day!

Roundworms and Disease 1. Trichinosis (trichinella worm)  - cysts within the muscles are consumed (undercooked food)  - worm grows in intestine - forms cysts in the muscles of the new host  - symptom: terrible pain in muscles

Roundworms and Disease 2. Filarial Worms - found in Tropical regions of Asia - usually transmitted by mosquitoes - causes elephantiasis 3. Ascarid Worms (common roundworm)  - lives in intestine - eggs are passed out in the feces

Roundworms and Disease 4. Hookworms - burrow into the skin from soil - mature in the intestines -hooks used to attach and suck blood

Can humans get roundworms from their pets?