Roundworms
By: Paige Barnett
Germ Layers
They have three germ layers. They are the ectoderm, mesoderm, and endoderm.
Cephalization
It does not show this.
Segmentation
They are unsegmented.
Digestive System
They have a definite digestive system that runs the length of their bodies. It has a mouth, pharynx, intestine and anus.
Respiratory System
They don't have a formal respiratory system. They breathe through diffusion.
Excretory System
They have an anus near it's rear end and a series of excretory tubes that end in an excretory pore.
Reproduction
They reproduce sexually. When it is time to reproduce, the sperm cells pass through the spicule. Over 200,000 eggs can be deposited at once in the soil once they are fertilized.
Support
They do not have a skeleton.
Sources
http://www2.fiu.edu/~pitzert/flat.htm
http://waynesword.palomar.edu/trnov01.htm
http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html
http://www.baileybio.com/plogger/?level=picture&id=1474
http://plpnemweb.ucdavis.edu/nemaplex/taxadata/Nemata.htm
http://faculty.fmcc.suny.edu/mcdarby/animals&plantsbook/animals/04-Roundworms.htm
http://universe-review.ca/R10-33-anatomy.htm
http://www.mcwdn.org/Animals/Roundworms.html
http://sheppardsoftware.com/content/animals/animals/invertebrates/roundworm.htm
https://sites.google.com/site/roundworms69/excretion-2