Correct sequence of embryo development :

Options

A. Gamete `to` Zygote `to` Morula `to` Blastula `to` Gastrula
B. Gamete `to` Zygote `to` Blastula `to` Morula `to` Gastrula
C. Gamete `to` Neurula `to` Gastrula
D. Gamete `to` Neurula `to` Morula

Answer

To determine the correct sequence of embryo development, we can break down the stages as follows:

### Step-by-Step Solution:

1. **Gamete Formation**: The process begins with the formation of gametes, which are the male (sperm) and female (egg) reproductive cells.

**Hint**: Remember that gametes are haploid cells that combine during fertilization.

2. **Fertilization**: The sperm fertilizes the egg, resulting in the formation of a zygote, which is the fertilized egg.

**Hint**: Think of fertilization as the union of two gametes to form a diploid cell.

3. **Zygote Stage**: The zygote undergoes cleavage, which is a series of rapid cell divisions without growth, leading to the formation of two cells.

**Hint**: Cleavage is important for increasing the number of cells while maintaining the same overall size.

4. **Two-Cell Stage**: After the first cleavage, the zygote develops into a two-cell stage.

**Hint**: This is the initial division of the zygote.

5. **Four-Cell Stage**: The two-cell stage further divides to form a four-cell stage.

**Hint**: Each division doubles the number of cells.

6. **Morula Stage**: The four-cell stage continues to divide, resulting in an eight-cell stage known as the morula.

**Hint**: The morula resembles a solid ball of cells.

7. **Blastula Stage**: The morula transforms into a blastula, which is characterized by a fluid-filled cavity called the blastocoel.

**Hint**: The transition to blastula involves the formation of a hollow structure.

8. **Gastrula Stage**: Finally, the blastula develops into a gastrula, where the germ layers (ectoderm, mesoderm, and endoderm) begin to form.

**Hint**: Gastrulation is a critical phase where the basic body plan is established.

### Correct Sequence:
Thus, the correct sequence of embryo development is:
- Gamete Formation (egg and sperm)
- Zygote
- Morula
- Blastula
- Gastrula

### Final Answer:
The correct answer is: Gamete → Zygote → Morula → Blastula → Gastrula.