2. Natural Selection: The Four-Step Logic

The main engine of evolution is natural selection, an idea from Charles Darwin. It follows a clear four-step logic — remember it as V-I-S-T.

• Variation — individuals in a population differ.
• Inheritance — some of those differences are passed to offspring.
• Selection — more offspring are produced than can survive, so there is competition; individuals with helpful inherited traits tend to survive and reproduce more.
• Time — over many generations, the helpful traits become more common in the population.

Crucially, the environment decides which traits are 'helpful.' A trait that helps in one place (thick fur in the cold) may be unhelpful in another (the same fur in a hot desert). Selection has no goal — it simply favors whatever works right now, in this environment.

⚠️ Common misconception: traits do not appear because an organism needs them. Natural selection acts on variation that already exists; it doesn't create new traits on demand.

💡 Tip: V-I-S-T — Variation, Inheritance, Selection, Time. The environment is the 'judge.'