Polyspermy is prevented by:

Options

A. Fertilization cone
B. Fertilization membrane
C. Jelly coats
D. Tertiary membrane

Answer

**Step-by-Step Solution:**

1. **Understanding Polyspermy**:
- Polyspermy occurs when more than one sperm fertilizes a single ovum. This can lead to abnormal development and is not viable.

2. **Role of the Ovum**:
- The ovum has protective layers that prevent multiple sperms from fertilizing it. These layers are crucial for ensuring that only one sperm can penetrate the ovum.

3. **Receptors on the Ovum**:
- The surface of the ovum contains specific receptors known as fertilizing receptors. These receptors are essential for the recognition and binding of sperm.

4. **Sperm Interaction**:
- Sperm also has anti-fertilizing receptors on its head. When a sperm binds to the ovum's receptors, it triggers a response that blocks other sperms from attaching.

5. **Formation of the Fertilization Cone**:
- Upon successful binding of a sperm to the ovum, the structure of the ovum changes to form a fertilization cone, which helps in the penetration of the sperm.

6. **Creation of the Fertilization Membrane**:
- After the sperm enters the ovum, the vitelline membrane (a protective layer) transforms into a tough fertilization membrane. This membrane is critical as it prevents any additional sperm from entering the ovum.

7. **Conclusion**:
- The primary mechanism that prevents polyspermy is the formation of the fertilization membrane, which acts as a barrier to other sperm after the first sperm has successfully fertilized the ovum.

**Final Answer**: Polyspermy is prevented by the fertilization membrane.

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