History of Life

Fossil Record 1.Evidence about the history of life on Earth 2.How different organisms changed over time 3.What organisms lived during the same time periods 4.What organisms lived that are now extinct

Relative Dating Fossil’s age is estimated by comparison to other fossils Index fossils are found in specific layers and are used to estimate ages of others.

Radioactive Dating 1. Age is calculated based on the amount of radioactive isotopes contained in a sample 2. Carbon Dating measures the ratio of C-12 to C-14 ratio in a sample (60,000 yrs) 3. More C-12 = Older

Which process is more accurate? Radioactive dating gives an absolute age, while Relative Dating is an estimate.

Earth’s Early Atmosphere 1. Hydrogen Cyanide 2. Carbon Dioxide 3. Nitrogen 4. Hydrogen Sulfide 5. Water

First Organic Molecules Miller and Urey experimented with organic compounds Produced amino acids by passing electrical sparks through: Hydrogen, Methane, Ammonia and Water

How has the atmosphere changed? First Life evolved in the absence of Oxygen –Prokaryotes Then Photosynthetic bacteria Photosynthesis produces Oxygen which accumulated in the atmosphere

Oxygen… Deadly Poison? Oxygen accumulated and those organisms unable to adapt became extinct Other organisms evolved with different metabolic pathways, using oxygen for respiration

Origin of Eukaryotic Cells Endosymbiotic Theory: Eukaryotes arose from a symbiosis among prokaryotic organisms Mitochondria and Chloroplasts are organelles that were one thought to be independent organisms

Lynn Margulis – U Mass Amherst and Boston University

Anaerobic / Aerobic Ancient aerobic and photosynthetic bacteria may have been engulfed by primitive eukaryote Mitochondria and Chloroplasts are organelles that were one thought to be these independent organisms