Scientists have developed a classification scheme that categorizes all members of the animal kingdom, although there are exceptions to most “rules” governing animal classification (Figure). Animals are primarily classified according to morphological and developmental characteristics, such as a body plan. One of the most prominent features of the body plan of true animals is that they are morphologically symmetrical. This means that their distribution of body parts is balanced along an axis. Additional characteristics include the number of tissue layers formed during development, the presence or absence of an internal body cavity, and other features of embryological development, such as the origin of the mouth and anus.
Which of the following statements is false?
- Eumetazoans have specialized tissues and parazoans don’t.
- Lophotrochozoa and Ecdysozoa are both Bilataria.
- Acoela and Cnidaria both possess radial symmetry.
- Arthropods are more closely related to nematodes than they are to annelids.