Question

In sponges, fertilisation is ......(a)......and development is ....(b)......having a larval stage which is morphologically....(c)....from the adult.

(a) Internal, (b) indirect, (c)distinct
(a) Internal, (b) indirect, (c)similar
(a) external, (b) direct, (c)distinct
(a)External, (b) indirect, (c)similar

Answer 1

Sponges are the multicellular organisms whose body contain several pores. They belong to the phylum Porifera which mean pore bearing organisms. Sponges do not have nervous, digestive or circulatory systems.

Complete answer:
To solve this question we must study about the reproduction in sponges.
Reproduction in sponges.
Asexual reproduction mainly takes place through budding, fragmentation or by formation of gemmule.

Sexual reproduction- the sponges are hermaphrodite. They do not have a definite reproductive organ. The sperms are produced by the choanocytes which form the spermatic cysts. The eggs are formed by the transformation of archaeocytes. The sperms burst out and fall into the osculum.
Mostly the fertilisation is internal. The eggs hatch to produce larvae(indirect development). The larvae are like balls of cells which have cilia and flagella for movement. It is called parenchyma. It looks distinct from the adult sponge. The mature larvae transforms into archaeocytes which look like miniature adult sponge.

Archeocytes are the totipotent amoeba like cells which are capable of transforming into any kind of cell. The choanocytes are the inner layer of cells which have flagella.

Hence, the correct answer is option (A)

Note: The indirect development involves the larval stage. The fertilised egg develops into an adult through the larval stage. Example-butterfly. Direct development does not involve larvae. Example-Humans.