Diversity of living organisms is due to `:`

Options

A. mutation
B. gradual change
C. long term evolutionary change
D. short term evolutionary change

Explanation

**Step-by-Step Solution:**

1. **Understanding Diversity:** The question asks about the diversity of living organisms. Diversity refers to the variety of species and forms of life present in the world.

2. **Species Count:** It is noted that there are approximately 1.5 to 1.7 million described species, with many more that are yet to be discovered. This indicates a vast array of life forms.

3. **Common Ancestor:** All living organisms share a common ancestor. This means that the diversity we see today has evolved from a single or a few ancestral species over time.

4. **Evolutionary Changes:** The diversity of species is primarily due to long-term evolutionary changes. These changes occur over extended periods and lead to the development of new species from common ancestors.

5. **Short-term vs Long-term Changes:** Short-term evolutionary changes are not sufficient to account for the vast diversity of species. It is the long-term changes that have allowed for significant adaptations and speciation.

6. **Role of Mutations:** While mutations play a role in evolution, they are typically small changes. They alone cannot explain the large number of species we observe today.

7. **Conclusion:** Based on the above points, the correct answer to the question is that the diversity of living organisms is due to long-term evolutionary changes.

**Final Answer:** The diversity of living organisms is due to long-term evolutionary changes.

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