Question

how is the entry of only 1 sperm and not many ensured into an ovum during fertilisation in humans?

Answer 1

So many sperms go in to the tube but the first one who reaches to ovum , fuse

Answer 2

During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces change in the membrane that block entry of additional sperms. Thus, it ensures that only one sperm can fertilise an ovum.