Natural Selection

Variation + Adaptation – increase an individuals chance of surviving and reproducing; happens with heritable traits


  • grasshoppers can be either yellow or green
  • green is an adaptation → blend with environment + are less visible to predators
  • green grasshoppers have a higher fitness than yellow → survive + reproduce more often
  • green grasshoppers became more common than yellow over time


  • genetic variation to produce different heritable traits
    • mutations, random assortments of genes
  • environmental forces
    • survival from predators
    • Example: bird beaks → same shapes are better for certain foods