Give the three key factors of the modern concept of evolution.

Explanation

### Step-by-Step Text Solution

1. **Understanding Evolution**: Evolution can be defined as an ordered change in organisms over time. The modern concept of evolution is based on three key factors that contribute to this process.

2. **Key Factor 1: Mutation**:
- **Definition**: Mutations are sudden changes in the chemistry of genes.
- **Impact**: These changes can lead to alterations in the genotype (the genetic makeup of an organism), which in turn can result in changes in the phenotype (the observable traits of an organism).
- **Type of Variation**: Mutations are considered non-continuous sources of variation, meaning they introduce distinct changes rather than gradual ones.
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