A new factor in the modern synthetic theory of organic evolution is

Options

A. sexual reproduction
B. mutation
C. isolation
D. natural selection

Answer

To solve the question regarding the new factor in the modern synthetic theory of organic evolution, we can analyze each option provided.

### Step-by-Step Solution:

1. **Understanding the Modern Synthetic Theory of Evolution**:
- The modern synthetic theory, also known as the modern synthesis, integrates Darwin's theory of natural selection with Mendelian genetics. It explains how evolution occurs through genetic changes in populations over time.

2. **Analyzing the Options**:
- **Option 1: Sexual Reproduction**:
- Sexual reproduction involves the combination of genetic material from two parents. While it is a crucial mechanism for genetic variation, it is not a new factor introduced in the modern synthetic theory. Therefore, this option is incorrect.

- **Option 2: Mutation**:
- Mutation refers to changes in the DNA sequence that can lead to new traits. This is indeed a new factor that was incorporated into the modern synthetic theory, as it provides the raw material for evolution by introducing genetic variation. Thus, this option is correct.

- **Option 3: Isolation**:
- Isolation refers to the separation of populations, which can lead to speciation. While it is an important concept in evolution, it is not a new factor in the context of the modern synthetic theory. This option is incorrect.

- **Option 4: Natural Selection**:
- Natural selection, proposed by Charles Darwin, explains how organisms better adapted to their environment tend to survive and reproduce. This concept has been a foundational element of evolutionary theory and is not a new factor in the modern synthesis. Therefore, this option is incorrect.

3. **Conclusion**:
- After analyzing all the options, the only new factor introduced in the modern synthetic theory of organic evolution is **mutation**.

### Final Answer:
The correct answer is **mutation**.

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