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8-2 NOTES: HISTORY OF LIFE CHAPTER 14 AGE OF EARTH The earth is about 4.5 billion years old How did we measure that? https://www.youtube.com/watch?v=H2_6cqa2cP4 AGE OF EARTH The earth is about 4.5 billion years old How did we measure that? • Radiometric Dating = calculating the age of an object by measuring proportions of radioactive isotopes RADIOMETRIC DATING Radioactive Isotope = an unstable form of an element, decays into stable element, gives off energy (radiation) • Ex. Carbon-14 decays into Nitrogen • Ex. Potassium-40 decays into Argon-40 RADIOMETRIC DATING Half-life = the time it takes for half of a radioactive isotope to decay • Ex. K-40 half life is 1.3 billion years PRACTICE The half life of carbon-14 is 5,730 years. If only 25% of the original amount of carbon-14 is left in an object, how hold it the object? PRACTICE The half life of carbon-14 is 5,730 years. If only 25% of the original amount of carbon-14 is left in an object, how hold it the object? 1.Determine how many half lives have elapsed. • 25% or ¼ = 2 half lives PRACTICE The half life of carbon-14 is 5,730 years. If only 25% of the original amount of carbon-14 is left in an object, how hold it the object? 1.Determine how many half lives have elapsed. • 25% or ¼ = 2 half lives 2.Multiply this by the known half life. • Carbon half life = 5,730 years • 2(5,730 yrs) = 11,460 years FIRST ORGANIC COMPOUNDS Spontaneous Origin: organic compounds developing from non-living chemical reactions SPONTANEOUS ORIGIN Oparin: (1920) Hypothesized that primitive Earth’s atmosphere was: • NH3 (ammonia) • H2 • H2O • CH4 (methane) No Oxygen! SPONTANEOUS ORIGIN Miller-Urey: (1953) Produced organic compounds (amino acids) based on the hypothesized composition of early earth’s atmosphere FIRST LIFE FORMS - THE FIRST CELLS Prokaryotes before eukaryotes FIRST LIFE FORMS - THE FIRST CELLS Prokaryotes before eukaryotes 3 major trends all interrelated: • Anaerobic Aerobic Inferences based on early earth environment having: 1. No Oxygen Gas (anaerobic) FIRST LIFE FORMS - THE FIRST CELLS Prokaryotes before eukaryotes 3 major trends all interrelated: • Anaerobic Aerobic Inferences based on early earth environment having: 1. No Oxygen Gas (anaerobic) 2. Many organic molecules for food (hetero) 3. Extreme harsh conditions (chemosynthetic) • Heterotrophic Autotrophic • Chemosynthetic Photosynthetic THE FIRST EUKARYOTES ENDOSYMBIOSIS THEORY • Mitochondria (aerobic prok) and chloroplasts (chemosynthetic prok) are thought to be prokaryotic cells that were engulfed by a bigger prokaryote. • Created mutual beneficial relationship • Bigger prokaryote provided a beneficial environment • Smaller prokaryote provided a source of energy THE FIRST EUKARYOTES ENDOSYMBIOSIS THEORY • Mitochondria (aerobic prok) and chloroplasts (chemosynthetic prok) are thought to be prokaryotic cells that were engulfed by a bigger prokaryote. Supporting Evidence: • Both organelles contain their own DNA • DNA is circular (like other prokaryotes) • Can replicate on their own. PUT THESE IN THE ORDER IN WHICH THEY ARE THOUGHT TO HAVE ORIGINATED ON EARTH 1. Anaerobic heterotrophic prokaryotes 2. Aerobic eukaryotes 3. Chemosynthetic prokaryotes 4. Photosynthetic prokaryotes Answer: 1, 3, 4, 2 SEQUENCE OF FIRST CELLS Anaerobic Heterotrophic Prokaryotes Chemosynthetic Prokaryotes Photosynthetic Prokaryotes Endosymbiosis Occurs Here! Aerobic Eukaryotes Photosynthetic Eukaryotes
