1. History of our Understanding of Life

2. How is Life Classified? A short history… 1700s 300s BC 1977 Aristotle Carl Linnaeus Carl Woese

3. How is Life Classified? Until the late 1800’s, scientists thought that all living things were either plant or animal. Period. But wait!

4. How is Life Classified? By the 1950s and 1960s, most biologists figured out that fungi, protists and bacteria did not fit in the categories that existed.

5. How is Life Classified? So, the understanding changed! Life was now divided into 5 Kingdoms: PlantAnimalProtistFungusBacteriaand…

6. How is Life Classified? And biologists made 2 divisions based on cell structure… BACTERIA -cells have no nucleus -they don’t have cellular structures like mitochondria! -they are called PROKARYOTES THE REST (PLANTS, ANIMALS, PROTISTS, FUNGI) -cells DO have a nucleus! -they all have cellular structures like mitochondria. -they are called EUKARYOTES But wait… we’re not done!

7. How is Life Classified? Turns out that about 30 years ago (ONLY 30 years ago!), a scientist in Illinois was studying bacteria and figured out that SOME kinds of bacteria were VERY different from other kinds of bacteria. Too different to group them together! So, he proposed yet another change and about 10 years ago, it happened…

8. The Three Domains