The phenomenon that is not part of Darwin's theory was :

Options

A. Survival of the fittest
B. Arrival to the fittest
C. Branching descent
D. Struggle for existence

Answer

To solve the question regarding which phenomenon is not part of Darwin's theory, we will analyze the given options based on our understanding of Darwin's principles.

### Step-by-Step Solution:

1. **Understand Darwin's Theory**:
- Darwin's theory primarily includes concepts such as natural selection, survival of the fittest, branching descent, and struggle for existence.
- The key idea is that organisms that are better adapted to their environment tend to survive and reproduce more successfully.

2. **Analyze the Options**:
- **Survival of the fittest**: This is a key concept in Darwin's theory, referring to the idea that individuals best adapted to their environment are more likely to survive and reproduce.
- **Arrival of the fittest**: This term is not used in Darwin's theory. Instead, Darwin emphasized the idea of "survival" rather than "arrival."
- **Branching descent**: This concept is part of Darwin's theory, referring to the idea that species evolve from common ancestors through a branching process.
- **Struggle for existence**: This is another fundamental concept in Darwin's theory, highlighting the competition for limited resources among organisms.

3. **Identify the Correct Answer**:
- From the analysis, the term that does not belong to Darwin's theory is **"arrival of the fittest."**

### Final Answer:
The phenomenon that is not part of Darwin's theory is **arrival of the fittest**.

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