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The simplest types of canal system in Porifera is
A. Ascon type
B. Leucon type
C. Sycon type
D. Radial type

Answer
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Hint: Members of phylum porifera are also known as sponges.
They are marine and asymmetrical animals.
These are multicellular animals and have a cellular level of organization.
Sponges or poriferas have a water transport system or canal system.

Complete answer:
Phylum Porifera is the smallest multicellular animal belonging to kingdom animalia.
The word porifera mainly refers to pore bearers or pore bearing species.
Phylum porifera is also known as sponges.
Some of the characteristics of phylum porifera are:
1. These are pore-bearing multicellular organisms.
2. The body has no organs.
3. They exhibit holozoic Nutrition.
4. The body is radially symmetrical.
Sponges consist of a water transport system or canal system.
Water enters through minute pores known as Ostia in the body wall into a central cavity known as spongocoel from where it goes out through the osculum.
This pathway of the canal system helps in food gathering, respiratory exchange and removal of waste products from the body.
Choanocytes or collar cells line the spongocoel and the canals.
The simplest type of canal system found in Sponges is Ascon type.
Sycon type and leucon type of canal systems are advanced canal systems which are produced by folding in the body wall of ascon type of sponges.
Digestion in porifera is intracellular.
The body is supported by a skeleton made up of spicules or spongin fibers.
Porifera are hermaphrodites which means eggs and sperms are produced by the same individual.
Examples of porifera are: Sycon, Spongilla, and Euspongia.

So, the correct option is option A. Ascon type.

Note: Phylum Coelenterata: They are aquatic mostly marine, sessile or free swimming, radial symmetrical animals.
The name cnidaria is derived from cnidoblasts or cnidocytes.
They have a central gastro-vascular cavity with a single opening mouth on hypostomes.
For example: Physalia, Adamsia, Pennatula.