Phylum Nematoda .

Phylum Nematoda

https://www.youtube.com/watch?v=X1YiIiPUQR8

ROUNDWORMS

Kingdom Animalia

Phylum Nematoda

--Unsegmented worms

--Pseudocoelom

("false coelom")

-- body cavity contains

organs

Characteristics

• Bilaterally symmetric

• Body has more than two cell layers, tissues  and organs

• Body covered in a complex cuticle (protectivenoncellular layer of roundworms)

• Has a nervous system with pharyngeal nerve ring.

• Has no circulatory system (no blood system)

• Respiration= diffusion

Digestive tract with 2 openings: mouth & anus

Feeding

Free-living - predators

Parasites - humans and

animals

Reproduction: Sexual

reproduction,

Separate sexes

(male & female)

Roundworms & Disease

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

https://www.youtube.com/watch?v=DC4ozHnm9bY&index=3&list=PLLACj7guzqJpyi94ecdzg2mzHdVb6NYDR

Filarial Worms - found in Tropical regions of

Asia

-- usually transmitted

by mosquitoes

-- causes elephantiasis

https://www.youtube.com/watch?v=dnWwHthkGkY

Ascarid Worms (common

roundworm)

- lives in intestine

- eggs are passed out in the feces

Most roundworms infect

dogs, but occasionally they

find their way into human

hosts

Hookworms

- burrow into the skin from soil

- mature in the intestines

--hooks used to attach and suck blood

https://www.youtube.com/watch?v=8zqSLIUv_oQ

C. elegans: A model organism●first organism to have DNA completely

sequenced●It is a very simple, free living roundworm

https://www.youtube.com/watch?v=v4ePpLoS6xw

References

• Biology Corner• http://www.earthlife.net/inverts/nematoda.html