Question

enumerate the classes of porifera and their corresponding nature and composition of their skeleton

Answer 1

The phylum Porifera is divided into three classes :
1. Calcarea
2. Hexactinellida
3. Desmospongiae

1. Calcarea
- The skeleton consists of calcareous spicules.
- Choanocytes are releatively large.
- They are all marine and inhabit shallow water.
- Example; Scypha,Leucosolenia.

2. Hexactinellida
- The skeleton consists of siliceous spicules.
- The choanocytes are small.
- They are all marine and inhabit deep water.
- Example; Euplectella, Hyalanema.

3. Desmospongiae
- The skelton consists of siliceous spicules or spongin fibres.
- The choanocytes are small.
- They occur in shallow and deep sea as well as in fresh water.
- Example; Spongilla, Poterion.

Answer 2

The phylum Porifera is divided into three classes :

1. Calcarea
2. Hexactinellida
3. Desmospongiae