Which one of the following correctly describes the homologous structures?

Options

A. Organs with anatomical similarities, but performing different functions.
B. Organs with anatomical dissimilarities, but performing same function.
C. Organs that have no function now, but had an important function in ancestors
D. Organs appearing only in embryonic stage and disaappearing later in the adult.

Answer

To determine which option correctly describes homologous structures, let's analyze the definitions and characteristics of homologous structures step by step.

### Step-by-Step Solution:

1. **Understanding Homologous Structures**:
- Homologous structures are anatomical features in different species that share a common ancestry. Despite having different functions, they exhibit similar structural features.

2. **Evaluating the Options**:
- **Option 1**: "Organ with anatomical similarity but performing different functions."
- This option correctly describes homologous structures. For example, the forelimbs of humans, whales, and bats have similar bone structures but serve different purposes (grasping, swimming, and flying, respectively).

- **Option 2**: "Organ with anatomical dissimilarity but performing the same function."
- This describes analogous structures, not homologous ones. An example would be the wings of insects and birds, which serve the same function (flying) but have different anatomical structures.

- **Option 3**: "Organ have no function now but had an important function in ancestors."
- This describes vestigial organs, such as the human appendix, which are remnants of structures that had important functions in ancestral species.

- **Option 4**: "Organ appearing only in embryogenic stage and disappearing later in adult."
- This option refers to structures that may be present during embryonic development but do not persist in the adult form, which is not a defining characteristic of homologous structures.

3. **Conclusion**:
- The correct description of homologous structures is given in **Option 1**: "Organ with anatomical similarity but performing different functions."

### Final Answer:
**The correct option is: Organ with anatomical similarity but performing different functions.**

---