What is produced when a haploid egg and a haploid sperm unite?

• A. Blastula
• B. Zygote
• C. Ovum
• D. Fetus

Answer: (B)

When a haploid egg and a haploid sperm unite, the primary result is the formation of a zygote. This zygote represents the first diploid cell of a new organism and contains a complete set of chromosomes, half from the mother (via the egg) and half from the father (via the sperm).

The zygote undergoes subsequent cell divisions and differentiation, eventually leading to the development of a multicellular organism. This process establishes the foundation for the entire development of the organism, transitioning from a single-cell stage to more complex structures.

In contrast, a blastula is a later developmental stage that arises after the zygote undergoes cleavage, while an ovum refers specifically to the mature egg cell before fertilization, and a fetus is a more advanced developmental stage that follows embryonic development, which also begins from the zygote. Thus, the correct answer captures the immediate outcome of the fertilization event that initiates the life cycle of the organism.