Lineages change over times and sometimes diverge (speciate) Natural selection occurs and leads to adaptation. If life on earth evolved from a single ancestor we should see: Some traits held in common by all life. Evidence of changes in the organisms present on earth over time. Evidences that organism arise from previous organisms: transitional forms, vestigial characters, common pathways underlying development. Protest diversity (habitat, structure, reproduction, metabolism, locomotion) Properties of life conditions that must be met to be alive. Earth was formed ~4. 6 billion years ago. Emergent properties = complex patterns that are the outcome of simple processes. Ex// the shape of moving school of fish = emergent property or individual decisions (avoiding risks) Oparin-haldane hypothesis: chemicals in atmosphere of primordial earth + energy = formation of organic molecules required for life. Deep-sea vent hypothesis: chemicals in deep sea + heat energy + nutrient sources = formation of organic molecules required for life.