Here's why:

* Function: Both pollen and sperm cells are male gametes, meaning they carry the male genetic material needed for fertilization.

* Structure: While the structures are different, they both contain a nucleus with the genetic material (DNA). Pollen grains are often protected by a tough outer wall, while sperm cells have a tail for movement.

* Purpose: Both pollen and sperm cells are crucial for sexual reproduction. Pollen fertilizes the egg cell within the flower, while sperm fertilizes the egg cell within the female reproductive system.

While the structure of pollen and sperm cells differ, their fundamental function of carrying genetic information and initiating fertilization is strikingly similar.