Question

The first cell of the human being formed after the sperm from the male parent and egg from the female parent unite is called:

• A. Zygote
• B. Ovum
• C. Embryo
• D. Blastocyst

Hint:

Keep the precise chronological sequence of early prenatal development in mind:
\[ \text{Sperm} + \text{Ovum} \rightarrow \text{Zygote} \rightarrow \text{Morula} \rightarrow \text{Blastocyst} \rightarrow \text{Embryo} \rightarrow \text{Fetus} \]

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Human development begins at fertilization, which is the biological process where a male gamete (sperm) fuses with a female gamete (ovum).

Step 2: Detailed Explanation:
- Ovum: The mature female reproductive cell, or egg, prior to fertilization.
- Zygote: The single-celled diploid eukaryotic cell formed immediately upon the successful fusion of the haploid sperm and haploid egg. This represents the absolute first stage of a new individual's life cycle.
- Embryo: The early developmental stage of a multicellular organism, starting after the zygote begins to divide (around the second week after fertilization).
- Blastocyst: A specialized structural stage of development in early mammalian embryos, consisting of an inner cell mass, a fluid-filled cavity, and an outer trophoblast layer, occurring about 5--6 days post-fertilization.

Step 3: Final Answer
Thus, the first cell formed upon fertilization is called the zygote.