What is common in birds and mammals?

Options

A. Presence of claws
B. Bipedal
C. Four chambered heart
D. Presence of Pinna.

Answer

To answer the question "What is common in birds and mammals?", we can follow these steps:

### Step 1: Understand the Classification
- Birds belong to the class Aves, while mammals belong to the class Mammalia. Both classes fall under the sub-phylum Vertebrata, which means they share certain characteristics due to their vertebrate nature.

**Hint:** Look for classifications and groupings in biology to understand relationships between different organisms.

### Step 2: Identify Common Characteristics
- We need to identify characteristics that are shared between birds and mammals. Some options might include features like claws, bipedalism, heart structure, and external ear structures (pinna).

**Hint:** Consider anatomical and physiological traits that might be present in both groups.

### Step 3: Evaluate Each Option
1. **Presence of Claws**:
- Claws are primarily found in birds, specifically on their hind limbs. This is not a common feature in mammals.

**Hint:** Think about which species exhibit specific traits and whether those traits are universal across the groups.

2. **Bipedalism**:
- Bipedalism is characteristic of birds, as they primarily walk on two legs. While some mammals can be bipedal, it is not a common trait across all mammals.

**Hint:** Consider how animals move and whether that movement is shared by both groups.

3. **Chambered Heart**:
- Both birds and mammals have a four-chambered heart, which is a significant characteristic that aids in efficient circulation. This is a common feature.

**Hint:** Focus on organ systems, particularly the circulatory system, to find shared features.

4. **Presence of Pinna**:
- The pinna, or external ear structure, is found in mammals but not in birds. Thus, this is not a common feature.

**Hint:** Look for structures that are unique to one group and not shared with the other.

### Step 4: Conclusion
- The common characteristic between birds and mammals is the presence of a **four-chambered heart**. This feature is crucial for their efficient circulatory system and is a defining trait of both classes.

**Final Answer:** The common feature in birds and mammals is the **four-chambered heart**.