An Introduction to Zoology
Chapter 11: The Bilateria: Acoelomate Lophotrochozoans:
The Bilateria:
In the two previous chapters, we discussed the phyla
Cnidaria and
Ctenophora, the
diploblastic,
radially-symmetrical animals that are collectively known as the
Radiata. All other animals are
triploblastic and
bilaterally symmetrical, and so are collectively known as the
Bilateria.
All of the Bilateria have elongated, bilaterally-symmetrical bodies, at least during the embryo stage. Some of the Bilateria are radially-symmetrical as adults, it’s true, but all of them develop from bilaterally-symmetrical embryos. Most of the Bilateria also show some degree of
cephalization, meaning that their sense organs are concentrated at the
anterior end to form a
head.
Almost all of the Bilateria have their sense organs and neural tissues
concentrated at the anterior end of the body. This concentration of sensory
and neural tissues at the anterior end of the body is known as cephalization.
The remaining articles in this series will focus on the various phyla within the
clade Bilateria. First, though, we’ll briefly discuss bilaterian classification and diversity.
Introduction
What are the symptoms of a liver fluke infection? I like sushi and has eaten plenty in my life. They were cooked though, or so I thought.
Linear Mode
