A group of grass hoppers - some green and some brown lived in grassland having dry bushes and dry grass.
Name this phenomenon

Explanation

**Step-by-Step Solution:**

1. **Understanding the Environment**: The question describes a grassland with dry bushes and dry grass. This environment has changed from being green to brown due to climatic conditions.

2. **Identifying the Grasshoppers**: There are two types of grasshoppers mentioned: green and brown. The green grasshoppers are less camouflaged in the brown environment, while the brown grasshoppers blend in better.

3. **Variation and Adaptation**: Over time, some green grasshoppers may have undergone a variation that allowed them to change color to brown. This adaptation helps them survive better in their environment.

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