During fertilisation, a sperm comes in contact with a specific layer of the ovum and induces changes in the membrane that block the entry of additional sperms. Identify this layer and its structural nature.

Step-by-step solution

During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum. This contact induces changes in the membrane that block the entry of additional sperms, thereby preventing polyspermy. The zona pellucida is a non-cellular (acellular) glycoprotein layer secreted by the secondary oocyte itself. The corona radiata, on the other hand, is the outer cellular layer formed by granulosa cells. Thus, the correct layer responsible for the polyspermy block is the zona pellucida, and it is non-cellular i