PHYLA NEMATODA By: Alex Palasz, Alex Roszczyk, Danielle Perri, Vicky Moskal

GERM LAYERS  3 germ layers: endoderm, mesoderm, and ectoderm.  Nematodes are considered triploblasts because they have three germ layers.

SYMMETRY  Bilateral symmetry

COELOM  Nematodes have a pseudocoelom because they have a body cavitiy that is lined with mesoderm and endoderm as opposed to just mesoderm.

DIGESTIVE TRACT  Tube-like digestive tract with a mouth and an anus.

CEPHALIZATION  Centralization of nerves in the head region.  Nematodes have a rear nerve ring around the area of the pharynx.

SEGMENTATION  Non-segmented.

SKELETON & APPENDAGES  The hydro-skeleton maintains high water pressure in the nematode to keep its structure.  They have a tough elastic outer-cuticle that is used for movement.  The flexibility of the muscles combined with the hydro-skeleton allows the nematode to swim in a “whip-like” movement.

CIRCULATORY SYSTEM  None  The outer-cuticle of the nematode allows nutrients and necessary materials to flow into the nematode and through its body through diffusion.

RESPIRATORY SYSTEM  None  The outer cuticle is permeable to water and gasses so it is used to breathe and absorb necessary nutrients.

REPRODUCTION  Nematodes reproduce sexually.  They reproduce through internal fertilization. In most species of nematodes, organisms are separated by sexes and the females tend to be larger.

MALE VS. FEMALE BODIES

HABITAT  Nematodes usually inhabit water, soil, and bodies of other plants or animals.  As many as 1 million nematodes inhabit one square yard of soil.