Urinary bladder is absent in

Options

A. Aves
B. Reptiles
C. Amphibians
D. Mammal

Answer

**Step-by-Step Solution:**

1. **Understanding the Urinary Bladder**: The urinary bladder is a sac-like structure in many animals that temporarily stores urine before it is excreted from the body.

2. **Identifying the Groups of Animals**: The question asks in which group of animals the urinary bladder is absent. We need to consider different classes of animals, such as mammals, reptiles, amphibians, and birds.

3. **Analyzing Birds**: Birds belong to the class Aves. It is important to note that birds have specific adaptations for flight, which influence their body structure.

4. **Reason for Absence in Birds**: The urinary bladder is absent in birds primarily because they need to maintain a lightweight body for efficient flight. Having a urinary bladder would add unnecessary weight.

5. **Conclusion**: Based on the analysis, we can conclude that the urinary bladder is absent in birds (class Aves).

**Final Answer**: Urinary bladder is absent in birds (class Aves).

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