Answer:
fertilization
Step-by-step explanation:
Fertilization is the process whereby the nucleus of a male gamete fuses with the nucleus of a female gamete to a form a diploid zygote. This occurs in the oviduct following copulation. Both the male and female gamete are haploid. They contain half the number of chromosomes after successive meiosis.
When the sperm comes into contact with the egg, the acrosome bursts open and releases lytic enzymes which dissolve the egg membrane. Inside the cytoplasm of the ovum the head of the sperm releases haploid male nucleus.