KEY CONCEPT The origin of life on Earth remains a puzzle.

1. KEY CONCEPT The origin of life on Earth remains a puzzle.

2. Earth was very different billions of years ago. • There have been many hypotheses of Earth’s origins. • The most widely accepted hypothesis of Earth’s origins is the nebula hypothesis. • Sometimes also called the Big Bang Theory • Age of Earth: 4.5-4.6 billion years old https://vimeo.com/11188228

3. https://vimeo.com/11188228

4. electrodes “atmosphere” water “ocean” heat source amino acids Several sets of hypotheses propose how life began on Earth. • There are two organic molecule hypotheses. • Miller-Urey experiment

5. electrodes “atmosphere” water “ocean” heat source amino acids The Miller-Urey Experiment was based on Oparin’s Hypothesis: • Early Earth was warm, with lightning • Gases present: Water vapor, Hydrogen, Ammonia (NH3), Methane (CH4) • These combined to make first organic molecules. • The Miller-Urey Experiment made amino acids.

6. Meteorite Hypothesis • Amino acids may have arrived on Earth through meteorite or asteroid impacts. • Evidence: Scientists have found amino acids on meterorites.

7. Iron-sulfide bubbles hypothesis • Biological molecules first combined in compartments of chimmney-like structures on ocean floor • Compartments were first cell membranes. • There are different hypotheses of early cell structure.

8. Lipid membrane hypothesis • Lipid spheres (liposomes) could form around a variety of organic molecules, acting as early cell membranes. • There are different hypotheses of early cell structure.

9. A hypothesis proposes that RNA was the first genetic material. • Ribozymes are RNA molecules that catalyze their own replication. • DNA needs enzymes to replicate itself.