Question

Process by which two cells from different parents unite to produce the first cell of a new organism.

Answer 1

Answer:

Fertilization or fusion  of  gametes

Explanation:

Fertilization is a process in which male gamete (sperm) from male parent  fuses with the female gamete (egg) from female parent.

Fertilization results into a diploid zygote which is the first cell of the new organism.

The zygote soon divides by the repetitive mitotic division to form multiple cells. The multiple cells undergo several changes to develops into embryo.

Answer 2

I think the answer to your question is sexual reproduction.