Final answer:
Double fertilization is a process in angiosperms involving one sperm cell fusing with an egg to form a zygote and another with two polar nuclei to create endosperm. This provides advantages such as energy conservation and a readily available food source for the embryo, contributing to the success of angiosperms.
Step-by-step explanation:
Double fertilization is a unique and crucial process in the reproductive cycle of angiosperms, or flowering plants. When pollen is transferred to the stigma of a flower, it germinates, and a pollen tube grows to allow the transfer of two sperm cells into the ovule. Once inside the ovule, one sperm cell fertilizes the egg, forming a diploid zygote, which will develop into the future plant embryo. The other sperm cell fuses with two polar nuclei to form a triploid endosperm, which serves as a food reserve for the developing embryo. This simultaneous fertilization of the egg and the central cell gives rise to both the next generation of plant (embryo) and the nutritive tissue that will support its early growth (endosperm), thereby maximizing the chances of successful seed development.
This double fertilization offers several advantages to angiosperms. It ensures that the endosperm only develops in ovules where the egg has been fertilized, which conserves energy. Furthermore, the formation of the endosperm provides the developing embryo with a readily available food source, contributing to the efficiency of seed development and thus, potential success in germination and growth. This process has contributed to the evolutionary success and diversity of angiosperms, enabling them to become the most widespread and varied group of plants on Earth.