Deposition of calcareous shell around zygote occurs in

Options

A. birds and reptiles
B. birds and mammals
C. mammals and reptiles
D. all of these.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the deposition of a calcareous shell around the zygote. A calcareous shell is primarily made of calcium carbonate and serves as a protective layer.

2. **Identifying the Context**: The deposition of a calcareous shell is typically associated with oviparous animals, which are organisms that lay eggs.

3. **Examples of Oviparous Animals**: Common examples of oviparous animals include birds and reptiles. These animals produce eggs that are often surrounded by a calcareous shell for protection.

4. **Differentiating Between Oviparous and Viviparous**: It is important to distinguish between oviparous animals (like birds and reptiles) that lay eggs and viviparous animals (like most mammals) that give birth to live young. Viviparous animals do not have a calcareous shell surrounding their zygotes since they develop the embryo inside their bodies.

5. **Conclusion**: Based on the above analysis, the correct answer to the question is that the deposition of a calcareous shell around the zygote occurs in birds and reptiles.

**Final Answer**: The deposition of a calcareous shell around the zygote occurs in birds and reptiles.

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