Q.Explain the different methods of reproduction occuring in sponges.

Gemmules are internal buds — resistant, undifferentiated cell masses — by which sponges reproduce asexually and survive unfavourable conditions.

Sponges (Phylum Porifera) reproduce asexually chiefly by budding. In many freshwater sponges, this budding takes the internal form of gemmule formation: a cluster of totipotent cells called archaeocytes aggregates internally and becomes surrounded by a tough, protective coat (often reinforced with spicules), forming a gemmule. Gemmules are highly resistant structures that allow the sponge to survive adverse conditions such as desiccation or cold, which would kill the parent sponge itself. When favourable conditions return, the gemmule germinates, the archaeocytes emerge and differentiate, and grow into a new sponge — a clear example of asexual reproduction that does not involve gametes.

Gemmules are asexual reproductive buds characteristic of sponges (Porifera).

Gemmules are masses of archaeocyte cells surrounded by a hard, resistant, spiky protective coat, produced internally by freshwater sponges (Porifera), typically under unfavourable conditions (e.g., drying of the water body or winter). When conditions become favourable again, the gemmule germinates and releases cells that develop into a new sponge — this is a form of asexual reproduction. Amoeba reproduces by binary fission (and occasionally by multiple fission through spore formation, but not gemmules); Hydra reproduces asexually by budding, not gemmules; Penicillium (a fungus, note the spelling in the option) reproduces via spores, not gemmules. Only sponges are known for gemmule formation, so option (d) is correct.