What are the anatomical structures called that share a common ancestry?

Options

A. Analogous structures
B. Homologous structures
C. Evolutionary structure
D. Vestigial structures.

Answer

To answer the question "What are the anatomical structures called that share a common ancestry?", we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Types of Structures**:
- There are different types of anatomical structures in biology, including homologous structures, analogous structures, vestigial structures, and evolutionary structures.

2. **Definition of Homologous Structures**:
- Homologous structures are defined as traits that are shared due to a common ancestry. This means that these structures have a similar origin and are derived from a common ancestor, even if they may serve different functions in the present-day organisms.

3. **Examples of Homologous Structures**:
- A classic example of homologous structures is the forelimb of different animals such as humans, birds, and whales. Despite their different functions (e.g., grasping, flying, swimming), the underlying bone arrangement is similar, indicating a shared ancestry.

4. **Distinguishing from Other Structures**:
- **Analogous Structures**: These are features of different species that are similar in function but differ in structure and do not share a common ancestor.
- **Vestigial Structures**: These are structures that have lost their original function through evolution and are remnants of ancestral species.
- **Evolutionary Structures**: These are structures that develop due to environmental changes or the needs of the time, but they do not necessarily indicate a common ancestry.

5. **Conclusion**:
- The anatomical structures that share a common ancestry are referred to as **homologous structures**.

### Final Answer:
The anatomical structures that share a common ancestry are called **homologous structures**.

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