AP BIOLOGY

Detailed explanation-1: -There is no sperm present in a pollen grain. A pollen grain is a tiny male plant, a male gametophyte (gamete-forming plant). He is a multicellular organism (usually two cells in flowering plants, but more in the case of gymnosperm pollen) capable of producing sperm if he gets an opportunity.

Detailed explanation-2: -Pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower.

Detailed explanation-3: -Each pollen grain is a single cell containing two male gametes. Once mature, the anther splits open and pollen is released. Both male gametes are involved in fertilisation, resulting in formation of a zygote and an endosperm.

Detailed explanation-4: -The sperm cells of a flowering plant are contained in pollen grains. Pollination occurs when pollen grains are transported from anthers to stigmas.

Detailed explanation-5: -Male reproductive organs generate pollen grains, which produce pollen tubes, each consisting of a vegetative cell that engulfs two immotile sperm cells2.