Find out the correct sequence in embryonic development of animal:

Options

A. cleavage, zygote, fertilization, morula, glastula, gastrula
B. Fertilization, zygote,cleavage, morula, blastula,gastrula
C. Fertilization, cleavage, morula, zygote, blastula, gastrula
D. Fertilization, zygote, blastula, morula, cleavage, gastrula

Answer

To find the correct sequence in embryonic development of animals, we need to understand the stages that occur after fertilization. Here is the step-by-step solution:

### Step-by-Step Solution:

1. **Fertilization**: The process begins with the fertilization of the male and female gametes (sperm and egg), which occurs in the female's reproductive tract. This is the first step in embryonic development.

2. **Zygote Formation**: After fertilization, a single cell called the zygote is formed. This zygote contains genetic material from both the sperm and the egg.

3. **Cleavage**: The zygote undergoes a series of mitotic divisions known as cleavage. This process results in the formation of multiple cells from the zygote without an increase in overall size.

4. **Morula Formation**: Following cleavage, the cells continue to divide and form a solid ball of cells known as the morula. The morula typically consists of 8 to 16 cells.

5. **Blastula Formation**: The morula then develops into a hollow structure called the blastula. The blastula is characterized by the presence of an inner cell mass and an outer layer known as the trophoblast.

6. **Gastrula Formation**: The blastula undergoes further differentiation and folding to form the gastrula. The gastrula is a cup-shaped structure that contains three primary germ layers: ectoderm, mesoderm, and endoderm.

7. **Embryo Development**: From the gastrula stage, further differentiation occurs, leading to the development of the embryo and eventually the fetus.

### Correct Sequence:
Based on the above steps, the correct sequence in embryonic development is:
- Fertilization → Zygote → Cleavage → Morula → Blastula → Gastrula

### Final Answer:
The correct option is **B**: Fertilization followed by Zygote, Cleavage, Morula, Blastula, Gastrula.

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