Question

Arrange the following stages in sequence shown for human embryogenesis: A. Zygote, B. 8-cell stage, C. Gastrula, D. Blastula, E. Morula Choose the correct answer from the options given below:

• A. A, B, C, E, D \
• B. A, B, E, D, C \
• C. A, B, D, C, E \
• D. B, A, C, E, D

Hint:

Remember the classic developmental sequence: Zygote $\rightarrow$ Morula (solid ball) $\rightarrow$ Blastula (hollow ball) $\rightarrow$ Gastrula (three layered embryo).

Answer 1

The Correct Option is B

Step 1: Concept Embryogenesis is the developmental timeline that begins at fertilization and progresses through rapid cell divisions and structural rearrangements to shape the early embryo.

Step 2: Meaning The early embryo transitions through distinct structural forms as it grows from a single cell into a multilayered organism.

Step 3: Analysis Let us follow the chronological stages of early development: 1. Fertilization joins sperm and egg to create a single-celled diploid Zygote (A). 2. The zygote undergoes cleavage divisions, quickly reaching the early 8-cell stage (B). 3. Continued division produces a solid, mulberry-like ball of cells called a Morula (E). 4. Fluid accumulates inside the morula, hollow-out the center to form a fluid-filled sphere called a Blastula or blastocyst (D). 5. Cells migrate internally during gastrulation, transforming the single-layered sphere into a three-layered structural form called the Gastrula (C).

Step 4: Conclusion The correct chronological order of these developmental milestones is A $\rightarrow$ B $\rightarrow$ E $\rightarrow$ D $\rightarrow$ C, matching option B. Final Answer: (B)