Correct sequence in development is :

Options

A. Fertilization `to` Zygote `to` Cleavage `to` Morula `to` Blastula `to` Gastrula
B. Fertilization `to` Zygote `to` Blastula `to` Morula `to` Cleavage `to` Gastrula
C. Fertilization `to` Cleavage `to` Morula `to` Zygote `to` Blastula `to` Gastrula
D. Cleavage `to` Zygote `to` Fertilization `to` Morula `to` Blastula `to` Gastrula

Answer

To determine the correct sequence in the development of an embryo, we need to understand the stages that occur after fertilization. Here’s a step-by-step breakdown of the process:

1. **Fertilization**: This is the first step where the sperm fuses with the ovum (egg) to form a single cell called the zygote.

2. **Zygote Formation**: After fertilization, the zygote is formed. This is a diploid cell that results from the fusion of the sperm and egg.

3. **Cleavage**: The zygote undergoes a series of rapid cell divisions known as cleavage. This process does not increase the overall size of the embryo but divides the zygote into smaller cells.

4. **Morula**: After several rounds of cleavage, the zygote develops into a solid ball of cells known as the morula. This typically occurs around the 8-12 cell stage.

5. **Blastula**: The morula then undergoes further cleavage and transforms into a hollow sphere of cells called the blastula. This stage is characterized by the formation of a fluid-filled cavity known as the blastocoel.

6. **Gastrula**: Finally, the blastula undergoes a process called gastrulation, where it develops into the gastrula. This stage involves the formation of germ layers that will eventually differentiate into various tissues and organs.

Based on this sequence, the correct order of development is:
- Fertilization
- Zygote
- Cleavage
- Morula
- Blastula
- Gastrula

Thus, the correct answer is **Option A**: Fertilization, Zygote, Cleavage, Morula, Blastula, Gastrula.