Digestive organs, circulatory system, and nerve cords are completely absent in
Ectoprocta
Platyhelminthes
Porifera
Mollusca
Annelida
Due in great part to its characteristic of having a fixed number of cells in the adult, Caenorhabditis elegans has become an important model research organism in developmental biology. To which phylum does C. elegans belong?
Annelida
Nematoda
Platyhelminthes
Arthropoda
Nemertea
A lophophore is a structure used by lophophorates for
