Polyspermy is common in

Options

A. Frog
B. Man
C. Birds
D. Sea urchin

Answer

### Step-by-Step Solution:

1. **Understanding Polyspermy**:
- Polyspermy refers to a condition where an egg is fertilized by more than one sperm. This results in the formation of a zygote with multiple sets of chromosomes.

2. **Chromosome Count in Polyspermy**:
- Normally, diploid organisms have two copies of each chromosome (one from each parent). In the case of polyspermy, the resulting zygote may contain three or more copies of each chromosome, leading to an abnormal genetic makeup.

3. **Consequences of Polyspermy**:
- The zygote formed through polyspermy is usually inviable, meaning it cannot develop into a viable embryo. This is because the genetic imbalance disrupts normal development.

4. **Occurrence of Polyspermy**:
- Polyspermy is more likely to occur in environments where sperm competition is high. This is often seen in certain species due to selective pressures.

5. **Identifying Common Instances of Polyspermy**:
- Among the options provided (frogs, man, birds, sea urchins), it is noted that polyspermy is commonly observed in certain groups such as reptiles, elasmobranchs (like sharks), and notably, birds.

6. **Final Answer**:
- Based on the information, the correct answer to the question "Polyspermy is common in" is **birds**.