Question

Pick out the correct statement:
a) In sponges, choanocytes line the spongocoel and canal.
b) Fertilization is internal and development is indirect in sponges.
c) Sponges exhibit cellular levels of organization as cells in them are arranged as loose cell aggregates.
d) All sponges are asymmetrical i.e. any plane that passes from the centre does not divide them into equal halves
A. a), b) and c) are correct
B. a) and d) are correct
C. b) and d) are correct
D. a), b) and d) are correct

Answer 1

This question deals with various features of sponges. Sponges are organisms of the animal kingdom and are classified into Phylum-Porifera. The organisms of this phylum are pore bearing and are the lowest multicellular animals. They are aquatic in habitat. They are sedentary, sessile and grow like plants.

Complete answer:
Option A. In this option, statement a), b) and c) are correct. Statement a) is correct about the features of sponges and reads about choanocytes which are flagellated collar cells that line the spongocoel and the canals. In statement b) reproductive features of sponges are talked and fertilization in sponges is internal. It takes place inside the body and the development is indirect. It includes a larval stage Amphiblastula before metamorphosing into an adult sponge. Similarly, statement c) is also correct which talks about cellular organization in sponges. Sponges are the simplest multicellular organisms which lack true tissues and have cellular aggregates as their body structure.
Option A is correct.
Option B. says statement a) and d) as correct. As we discussed earlier that statement a) is correct but statement d) is incorrect as not all sponges are asymmetrical while some are also radially symmetrical like Cliona have radial symmetry.
So, Option B is incorrect.
Option C. Based on discussions made for above options. This Option is also incorrect as it says statement-d) to be correct.
Option C is also incorrect.
Option D. is again an incorrect option as it says statement-d) to be correct which is against facts.
Option D is incorrect.

Hence, Option A is the correct answer.

Note:
Porifera are aquatic multicellular organisms with cell grade body organization. Species of sponges are known across the globe. Most of the sponges are marine but some may be freshwater organisms. Their body shape is vase or cylinder like. They are diploblastic organisms with a hollow cavity called spongocoel. They have a characteristic skeleton made of spicules and spongin fibers. They reproduce sexually as well as asexually.