Question

Which animal phylum has the lowest structural organization?

• A. Annelida
• B. Porifera
• C. Mammalia
• D. All of the above

Answer 1

The correct option is B Porifera

Sponges are primitive multicellular animals and have a cellular level of organization. The body is not organized into tissues and organs or systems. Hence sponges are able to regenerate the whole body even from a small piece. They have undifferentiated archaeocytes that help the animal to regenerate. They do not possess any structures that can be considered organs. For instance, sponges do not have stomachs or kidneys. Instead, sponge cells of various types are responsible for bodily functions, the day-to-day activities that sustain life.

So, the correct answer is option B.