1. The History of Life 14.2 The origin of Life

2. The Origin of Life: Early Ideas People saw maggots appear on rotting meat  People saw mice appear in food storage  Thought that living things sprouted from the non-living

3. The Origin of Life: Early Ideas  Spontaneous generation is the idea that non-living material can produce life

4. The Origin of Life: Early Ideas  In 1668 Francesco Redi showed that living things did not come from non- living

5. The Origin of Life: Early Ideas  People still believed that life must arise from somewhere –Maybe from some vital force in the air

6. The Origin of Life: Early Ideas  In mid-1800s Louis Pasteur showed that living things would not arise from air

7. The Origin of Life  Biogenesis – the idea that living things come only from other living things  Biogenesis became cornerstone of biology  But how did the first life on Earth begin?

8. The Origin of Life: Modern ideas  For life on Earth to begin –Molecules that contain carbon form  Organic molecules –Then are organized into complex molecules  Proteins, carbohydrates, nucleic acids

9. The Origin of Life: Modern ideas  1930s Russian Alexander Oparin said –Heat from lightning on the oceans triggered formation of organic molecules  1953 Americans Miller and Urey –Simulated the conditions of early Earth –Supported Oparin’s hypothesis

10. The Origin of Life: Modern ideas  1950s experiments showed that organic molecules in heated water form complex molecules like proteins, ATP  American Sydney Fox showed that amino acid chains can form protocells

11. The Origin of Life: Modern ideas  Protocells are large structures with a membrane that carry out life activities like growth and division  Protocells evolved to prokaryotes

12. The Origin of Life: Modern ideas  The first prokaryotes were –Anaerobic – without oxygen –Heterotrophs – don’t make own food

13. The Origin of Life: Modern ideas  Next: Archaebacteria –Prokaryotes that live in harsh environs –Autotrophs – make own food –Chemosynthesis – get energy from inorganic compounds in the environment

14. The Origin of Life: Modern ideas  Then: Prokaryotes that get food from photosynthesis  Start to make oxygen

15. The Origin of Life: Modern ideas  Eukaryotes evolve when prokaryotes team up –Proposed by American Lynn Margulis 1960