Human reproduction vocabulary: What is the correct term for the event when the nucleus of a sperm cell fuses with the nucleus of an egg cell to form a zygote?

Introduction / Context:
Precise terminology is important in reproductive biology. Several steps occur from mating to pregnancy; only one term refers specifically to the fusion of gamete nuclei to form a zygote.

Given Data / Assumptions:

• Sperm and egg nuclei join to create a diploid zygote.
• The question asks for the exact biological term for nuclear fusion of gametes.

Concept / Approach:
The correct term is fertilisation (also called syngamy or karyogamy, depending on emphasis). Other listed words describe broader processes or different stages and are not specific to nuclear fusion.

Step-by-Step Solution:

Verification / Alternative check:
Standard texts define fertilisation as the union of male and female gametes to form a zygote.

Why Other Options Are Wrong:

Common Pitfalls:
Using everyday language instead of precise biological terms.

Final Answer:
Fertilisation.