An ovule generally has a single embryo sac formed from a megaspore through

Options

A. Reduction divisions
B. Mitotic divisions
C. Mitotic division followed by meiotic division
D. Meiotic division followed by mitotic division

Explanation

**Step-by-Step Solution:**

1. **Understanding the Structure of the Ovule:**
- The ovule is a part of the female reproductive system in flowering plants, located within the ovary. It contains the embryo sac, which is crucial for reproduction.

2. **Formation of the Megaspore:**
- Inside the ovule, there is a tissue called the nucellus. Within the nucellus, a specialized cell called the megaspore mother cell (or megasporangium) is present. This cell is large and has a prominent nucleus and dense cytoplasm.

3. **Meiosis in the Megaspore Mother Cell:**
- The megaspore mother cell undergoes meiosis, a type of cell division that reduces the chromosome number by half. This process results in the formation of four haploid cells known as megaspores.

4. **Degeneration of Megaspores:**
- Out of the four megaspores produced, three typically degenerate, leaving only one functional megaspore.

5. **Development of the Embryo Sac:**
- The surviving megaspore undergoes a series of mitotic divisions. Initially, it is a single haploid cell with one nucleus. Through mitosis, this cell divides to produce two nuclei, which then migrate to opposite poles of the cell.

6. **Further Mitotic Divisions:**
- The process continues, with the single megaspore undergoing additional mitotic divisions, resulting in a total of eight nuclei within the embryo sac.

7. **Formation of the Embryo Sac Structure:**
- Eventually, cell walls form around these nuclei, leading to the development of the embryo sac, which consists of seven cells and eight nuclei. The arrangement includes:
- One egg cell and two synergids at one end (micropylar end).
- Two polar nuclei in the center (forming the central cell).
- Three antipodal cells at the opposite end (chalazal end).

8. **Conclusion:**
- The embryo sac is formed from a single megaspore through mitotic divisions, leading to the characteristic structure of the female gametophyte in flowering plants.

**Final Answer:**
The embryo sac in the ovule is formed from a megaspore through mitotic division.

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