Question

The branches Radiata and Bilateria of the Eumetazoa both exhibit:
A. Cephalization
B. Dominance of diploid life stage
C. A complete digestive tract with separate mouth and anus
D. Three germ layers in embryonic development

Answer 1

Hint: Multicellular animals show diploid life cycle. Radiata and Bilateria are multicellular animals. Bilateria are a more advanced branch.

Complete answer: Radiata and Bilateria are branches of eumetazoans.
1. Cephalization is an evolutionary process where the mouth, sense organs and nerve ganglia become concentrated at the front end of an animal, producing a head.
2. Radiata do not show cephalization, whereas Bilateria shows cephalization.
3. Radiata have radial symmetry whereas Bilateria have bilateral symmetry.
4. Every multicellular animal shows a diploid life cycle. It is also known as diplontic. In this life cycle haploid gametes are formed which are egg and sperm. They are known as gametophytes.
5. In diplontic life cycle, gametes undergo meiosis and the dominant and independent phase is the diploid sporophyte.
6. Radiata don’t have head and tail whereas Bilateria have a digestive tract with separate mouth and anus.
7. Radiata are diploblastic organisms which means they have 2- germ layers ie. ectoderm and endoderm whereas Bilateria are triploblastic organisms which means they have 3-germ layers ie. ectoderm, endoderm and mesoderm.

So, the answer is B. Dominance of diploid life cycle

Additional information:Two major groups of radiata are coelenterates and echinoderms.
Radiata are acoelomate whereas Bilateria have a coelom.

Note: Most of the Bilateria have primary larvae which swim with cilia and have an apical organ containing sensory cells.