Final answer:
The fusion of two gametes is called fertilization, which results in the formation of a diploid zygote. This is part of sexual reproduction, involving meiosis to produce haploid gametes.
Step-by-step explanation:
The fusion of two gametes is known as fertilization, and it produces a zygote. Gametes, such as sperm and eggs, are haploid cells that contain only one set of chromosomes. During the process of fertilization, these haploid gametes unite to form a diploid zygote, which contains two sets of chromosomes, one from each parent.
The diploid zygote will then undergo multiple rounds of mitosis to develop into a multicellular organism. This fusion is a key aspect of sexual reproduction, which includes the process of meiosis to produce the haploid gametes that will subsequently unite during fertilization. Meiosis involves two rounds of nuclear divisions, resulting in four genetically unique haploid daughter cells from the initial diploid parent cell.