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Phylum Nematoda (Roundworms)

These are simple ecdysozoans, the top picture here is of C. elegans which is a common model organism used to research neural development.

  • Roundworms / Threadworms
  • Compared to Annelids
  • Lack segmentation
  • Lack appendages
  • Lack eyes
  • One end is blunt, the other is pointed
  • Undergo molting
  • Simple body design
  • Absorb nutrients
  • Reproduce
  • Pseudocoelomate
  • Spiral cleavage
  • Some hermaphroditic
  • Direct developers
  • Eutelic: organism grows when cells increase in size, not by adding new cells
  • Born with set number of cells
  • Removing a cell in embryo will permanently remove the cell
  • Movement
  • Longitudinal: side to side
  • Free living
  • In organic substrates
  • Soil, freshwater, marine
  • Some are parasitic, some are important in medicine







Top: C. elegans
Bottom: Soy Bean Cyst Nematode with Egg
Photo by Bob Goldstein | CC BY

Practice: Nematodes

Which of the following features of Nematodes differentiates them from Annelids? (select all that apply)
checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.

checklist
Mark Yourself Question
  1. Grab a piece of paper and try this problem yourself.
  2. When you're done, check the "I have answered this question" box below.
  3. View the solution and report whether you got it right or wrong.