Question

The most distinctive character of the sponge is
A. Presence of choanocytes
B. Unicellular
C. Marine
D. Asexual reproduction

Answer 1

Hint: The Phylum porifers are strange, apparently lifeless and plant-like creatures commonly called the sponges. The body form varies considerably. Some sponges are vase-like or cylindrical, but the majority form flat, globular or irregular, or branching masses.

Complete answer: The unique features of sponges are as follows-
1. Pores all over the body
2. The cellular level of body organization.
3. A canal system of intercommunicating cavities for the passage of water current.
4. Lack of mouth and digestive cavity.
5. Chaonocytes lining the main cavity (spongocoel) or certain canals ( radial canals).

So, the correct answer is “Option A”.

Additional Information: The body wall consists of two imperfect layers: outer dermal layer, or pinacoderm, and inner chaonocytic layer or chanoderm.
The dermal layers consist of flat cells called pinacocytes and oval porocytes.
The chronic layer consists of characteristic flagellated collar cells or choanocytes.
Between these layers is a gelatinous material named mesophyll or mesenchyme.
It contains numerous free amoeboid cells, the amoebocytes, of several kinds, such as scleroblasts, spongioblasts, phagocytes, trophocytes, archaeocytes, collencytes, chromocytes, porocytes, and gland cells. The entire body bears pores.
Note: The sponges show advancement over protists in having a large multicellular body, a greater division of labour among the cells, male and female gametes in the form of spermatozoa and ova, and development from zygote by segmentation instead of by mere growth.