The idea not related to the Darwinian evolutionary theory is :

Options

A. survival of the best
B. struggle for existence
C. inheritance of acquired characters
D. origin of species by natural selection

Answer

To solve the question regarding which idea is not related to the Darwinian evolutionary theory, we can analyze each option provided.

### Step-by-Step Solution:

1. **Understand Darwinian Evolutionary Theory**:
- Charles Darwin's theory primarily revolves around natural selection, where organisms that are better adapted to their environment tend to survive and reproduce more successfully.

2. **Evaluate the Options**:
- **Option 1: Survival of the Best**:
- This phrase is often paraphrased from Darwin's idea of "survival of the fittest," which aligns with his theory. Thus, this option is related to Darwinian theory.

- **Option 2: Struggle for Existence**:
- This concept is also a part of Darwin's theory, referring to the competition among organisms for limited resources. Therefore, this option is also related to Darwinian theory.

- **Option 3: Inheritance of Acquired Characters**:
- This idea is attributed to Jean-Baptiste Lamarck, who proposed that traits acquired during an organism's lifetime could be passed on to its offspring. This concept is not part of Darwin's theory, making this option the correct answer.

- **Option 4: Origin of the Species by Natural Selection**:
- This is a fundamental aspect of Darwin's theory, as it describes how species evolve through the process of natural selection. Hence, this option is also related to Darwinian theory.

3. **Conclusion**:
- After evaluating all the options, the idea that is not related to the Darwinian evolutionary theory is **Option 3: Inheritance of Acquired Characters**.

### Final Answer:
The idea not related to the Darwinian evolutionary theory is **Inheritance of Acquired Characters**.