[A]: Homologous organs have similar struc- ture but different functions.
[R]: It is believed that homologous structures were created for different purposes and their present function is secondarily achieved out of necessity

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

**Step-by-Step Solution:**

1. **Understanding Homologous Organs**: Homologous organs are defined as organs that have a similar structure but perform different functions. This indicates that these organs share a common evolutionary origin.

2. **Divergent Evolution**: The concept of homologous organs is closely related to divergent evolution. This is the process where species that share a common ancestor evolve different traits or functions due to adapting to different environments or ecological niches.

3. **Example of Darwin's Finches**: A classic example of homologous organs and divergent evolution is seen in Darwin's finches. These birds originated from a common ancestor, a small black bird, but over time, they adapted to different food sources available in the Galapagos Islands. Some became frugivorous (fruit-eating), while others became insectivorous (insect-eating).

4. **Secondary Functionality**: The reason states that homologous structures were created for different purposes, and their current functions are achieved out of necessity. This means that while the original structure may have been adapted for a specific function, as species evolved, these structures took on new roles based on environmental demands.

5. **Conclusion**: Both the assertion and the reason are true. The reason correctly explains the assertion, as it illustrates how homologous organs can evolve from a common structure to serve different purposes in different species.

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