Question

Most primitive animals are

• A. Sponges
• B. Coelenterates
• C. Flat worms
• D. Round worms

Answer 1

The correct option is A Sponges

A. Sponges belong to phylum Porifera and are the most primitive of multicellular animals. These animals exhibit only cellular levels of body organisation and thus, are considered as the simplest forms among the metazoans.

B. Coelenterates are generally marine, aquatic, sessile or free swimming and are radially symmetrical. These are a step ahead of sponges in complexity.

C. Flat worms belong to phylum Platyhelminthes. These are found in marine, freshwater and damp terrestrial environment also.

D. Round worms belong to phylum Aschelminthes. Some are parasites while some are free living.

So, the correct answer is 'Sponges'.