## The Theory of Evolution

The theory of evolution explains how life on Earth changes over time through a process of descent with modification. Here are the core components:

### Basic Principles

- **Common Descent** - all living organisms share ancestors, with life branching out over billions of years
- **Variation** - individuals within a population differ from one another genetically
- **Heredity** - traits are passed from parents to offspring
- **Natural Selection** - individuals with traits better suited to their environment tend to survive and reproduce more successfully

### How It Works

Populations accumulate genetic changes (mutations) over generations. When certain variations improve survival or reproduction, those traits become more common over time. Given enough time and reproductive isolation, populations can diverge into distinct species.

### Key Supporting Evidence

- Fossil record showing gradual changes over time
- Genetic similarities between related species
- Observable evolution in bacteria, viruses, and other organisms
- Comparative anatomy and embryology
- Geographic distribution of species

### What It Covers
- Explains the **diversity of life**
- Explains why organisms are **adapted** to their environments
- Does **not** address the origin of the universe or the origin of life itself

### Important Note
It is called a "theory" in the scientific sense, meaning a **well-substantiated explanation** supported by extensive evidence, not a guess or speculation.

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