Why fertilization process in angiosperms is called as double fertilization?

Answer

### Step-by-Step Solution:

1. **Definition of Double Fertilization**: The term "double fertilization" refers to a unique process that occurs in angiosperms (flowering plants) during fertilization, where two fertilization events take place.

2. **Structure of Female Gametophyte**: In angiosperms, the female gametophyte is located within the embryo sac. This sac contains the female gamete, which is the egg cell.

3. **Entry of Male Gametes**: During fertilization, the pollen tube, which carries the male gametes, penetrates the embryo sac through the micropyle. Each pollen grain typically contains two male gametes.

4. **First Fertilization Event**: One of the male gametes fuses with the egg cell to form a zygote. This zygote will eventually develop into the embryo of the seed.

5. **Second Fertilization Event**: The second male gamete fuses with the two polar nuclei present in the central cell of the embryo sac. This fusion results in the formation of the endosperm, which provides nourishment to the developing embryo.

6. **Conclusion**: Since two fertilization events occur—one resulting in the formation of the zygote and the other resulting in the formation of the endosperm—the process is termed "double fertilization."