A4bbysashichez A4bbysashichez 08-12-2016 Biology contestada help please! The approximate age of Earth is: 6,000 years 150,000 years 4.5 billion years 13.5 billion years 2. On Aristotle's Scala Naturae, humans were: on the bottom rung on the top rung on the same rung as animals lower than plants 3. Which of these ideas is not a central theory for modern biology? evolution creationism cell theory gene theory