Where did life on earth begin? Origins of Life Where did life on earth begin?

What is the difference between a law and a theory? Law – a statement about the relationship between two or more things Describes what is happening, rather than why or how Laws describe what is happening, while theories seek to explain laws and why something is happening. Theories do not become laws, theories explain laws. Not all scientific laws have accompanying explanatory theories. Teacher will explain that “law” and “theory” mean different things in different disciplines. Theory – an explanation of why certain laws and facts exist A well tested explanation

Primitive Earth (Early Earth) So… WHERE DID LIFE BEGIN? HOW DID LIFE BEGIN? In Margins of your notes… Early Earth conditions: Atmosphere contained CO2, water, methane, and ammonia Lacked Oxygen (O2) Without oxygen, life (as we know it today) could not be supported

Key Ideas in the Origin of Life Spontaneous Generation (Abiogenesis): Living organisms develop from non-living matter Biogenesis: Living things can only arise from other living things

Failed Attempts at Explaining the Origin of Life Redi Tested hypothesis of Spontaneous Generation (Abiogenesis) Results: Disproved Spontaneous Generation Pasteur Actual success Sided with: Biogenesis Results: Life did not arise from non-life

EXPERIMENTS Redi Pasteur What do you think this diagram is saying?

SUCCESS STORIES Miller-Urey Experiment Simulated chemical conditions present on primitive earth Made organic compounds from inorganic material Compounds important to life could form on pre-biotic Earth

SUCCESS STORIES Endosymbiosis Endo- Inside Symbiotic- working Together Mitochondria and Chloroplast were prokaryote cells that were eaten by a eukaryote cell Prokaryotic cells gave rise to eukaryotic cells EVIDENCE: Both mitochondria and chloroplast have their own DNA

Endosymbiotic Theory