Question

In Demospongiae skeleton is composed of
A. Spongin fibers
B. Siliceous spicules
C. Both A and B
D. Keratin fibers

Answer 1

Hint: Demosponges are the largest class of organisms belonging to the phylum Porifera. These are soft-bodied creatures that possess a hard calcified skeleton. They are very porous in structure and their skeletons are made of siliceous spicules and spongin fibers.

Step by step answer:The Demosponges belongs to the phylum Porifera. These are named sponges due to their porous surface. These are predominantly marine dwelling organisms and can be found in a variety of vivid colors and shapes.
The most peculiar aspect of these organisms is that they have extremely long life spans ranging from 500 to 1000 years. This is mainly attributed to their skeletal structure. Demosponges have a leuconoid structure which refers to a porous jelly-like surface with a hard skeleton.
The skeletons of Demospongiae are made up of spicules. Spicules are structural elements made up of either silica or protein fibers such as spongin. In Demosponges, both types of spicules, siliceous spicules, and spongin fibers are present.

These spicules can be found in many different shapes and their arrangements are determinants of the class or genus of Demosponges.
Therefore, the correct option is C

Note: The Demosponges are soft-bodied organisms with hard internal skeletons. They are porous and have very long life spans. The skeleton is made up of spicules which are structural elements, made up of silica or protein fibers called siliceous spicules or spongin fibers. Spongin is a form of modified collagen that forms a fibrous mesh to provide structural support. Keratin fibers are proteins found in hair and nails of certain vertebrate organisms and not in Porifera.