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 have been traditionally classified according to two characteristics: body plan and developmental pathway. The major feature of the body plan is its symmetry: how the body parts are distributed along the major body axis. Symmetrical animals can be divided into roughly equivalent halves along at least one axis. Developmental characteristics include the number of germ tissue layers formed during development, the origin of the mouth and anus, the presence or absence of an internal body cavity, and other features of embryological development, such as larval types or whether or not periods of growth are interspersed with molting.
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.