Question

Which one of the following is correct?
A. All sponges are motile
B. Few are motile and rest are sessile
C. Few are sessile and rest are motile
D. All sponges are sessile

Answer 1

Hint: Sponges, the aquatic animals that constitute the Phylum Porifera, are the morphologically simple organisms that are multicellular, heterotrophic, parazoan and are characterized by the possession of a unique feeding system. They have a cellular level of organization, are hermaphrodites, and are filter feeders.

Complete answer:
Sponges are the most ancient and diverse group with the fossil records of some species dating back to 600 mya. There are almost 5000-1000 species in the Phylum Porifera of which most of them live in saltwater while around 150 live in marine water.
The ability of an organism to move from one place to another is called Locomotion. In Porifera, the larval stages are motile i.e., they have the ability to move/swim from one place to another. However, the adult sponges are sessile i.e., they are permanently attached to a surface or a substratum and do not show any type of locomotion. Therefore, all adult sponges are sessile.
Option D: All sponges are sessile is the correct option and all other options are irrelevant.

Hence, the correct answer is option (D)

Note: Generally, sponges are the sessile and sedentary invertebrate animal that attaches itself to solid surfaces from the intertidal zone to depths of 29,000 ft or more, where they can get sufficient food to grow. A few studies have shown that adult sponges in a few species can crawl slowly.