Which one of the following describes correctly the homologous organs ?

Options

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

Answer

To determine which option correctly describes homologous organs, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Homologous Organs**:
Homologous organs are those that have a similar anatomical structure but may serve different functions in different species. This similarity indicates a common evolutionary ancestor.

2. **Analyze the Given Options**:
- **Option 1**: "Organs which have no function now but had an important function in ancestors."
- This describes vestigial organs, not homologous organs.
- **Option 2**: "Organs appear only in embryonic stage and disappearing later in adulthood."
- This describes embryonic structures, not specifically homologous organs.
- **Option 3**: "Organs with anatomical similarities but performing the same function."
- This describes analogous organs, which serve similar functions but do not share a common ancestor.
- **Option 4**: "Organs with anatomical similarities but performing different functions."
- This correctly describes homologous organs.

3. **Identify the Correct Option**:
Based on the analysis, **Option 4** is the correct description of homologous organs.

4. **Provide Examples**:
Examples of homologous organs include the forelimbs of mammals such as humans, whales, bats, and cheetahs. All these limbs have similar bone structures (humerus, radius, ulna, carpals, metacarpals, phalanges) but serve different functions (grasping, swimming, flying, running).

5. **Conclude**:
Therefore, the correct answer is that homologous organs are those with anatomical similarities but performing different functions.