Early Earth and the Origin of Life AP Biology Crosby High School

History of Life 3.5 – 4 bya 3.5 – 2 bya Earth heavily bombarded Oldest fossils 3.5 bya 3.5 – 2 bya Rich fossil record of Prokaryotes Bacteria and Archae diverged Stromatolites

History (cont.) 2.7 bya 2.1 bya Emergence of Cyanobacteria O2 appeared in atmosphere First dissolved in Water Excess react with Iron Corrosive to chemical bonds 2.1 bya Eukaryotes evolved from symbiosis Chloroplasts could account for O2 increase

History (cont.) 1.2 bya Multicellular organisms arrise from cell divisions and specialization Larger multicellular org. arrive around 600 mya Snowball Earth (750 – 570 mya) Limited locations of organisms 1st major diversification occurred 570 mya

Early Cambrian Most animal Phyla originated in 1st 20 my of Cambrian 500 mya Fungi aid plants in taking water and nutrients Plants supply food for Fungi Plants transformed the landscape and allowed for terrestrial life Insect  Amphibians  Reptiles Reptiles became birds and mammals

Biogenesis Paradox Spontaneous Generation Louis Pasteur Life – from – Life Original Earth was very different Little atmospheric O2 Abundance of Energy

Four-Stage Hypothesis for Life Abiotic synthesis of small organic molecules Joining of small molecules to form polymers Origin of self-replicating molecules that made inheritance possible Packaging of molecules into “Protobionts”

Abiotic Synthesis of Monomers A.I. Oparin and J.B.S. Haldane (1920) O2 prevents chemical bonds from forming O3 blocks radiation Younger suns produce more UV Stanley Miller and Harold Urey (1953) Using early earth conditions a.a. were formed “Atmosphere” Contained H2O, H2, CH4, NH3 Electrodes created lightning

Formation of Abiotic Polymers Drip solutions of monomers onto hot sand, clay, or rock Rain or waves could have washed monomers onto rocks Polymers created and then washed back to sea

RNA as First Genetic Material Molecular Replication in RNA world Solution of nucleotides with RNA makes copies of RNA Thomas Cech (1980s): RNA acts as catalyst Natural Selection in RNA world RNA contained both a genotype and phenotype RNA may have held some a.a. long enough for them to bind

Protobionts form by Self Assembly Liposomes form when organic ingredients contain lipids Lipids organize into molecular bilayer Stored energy as membrane potential Liposomes sometimes engulf other liposomes Liposomes sometimes create smaller liposomes

5 Kingdom System Robert H. Whittaker (1969) Monera: All prokaryotes Eukaryotes: separated according to diet Plants: Produce food Fungi: Heterotrophic decomposers Animals: Ingestion followed by cavity digestion Protista: Eukaryotes that did not fit into Plant, Animal, or Fungi

3 Domain System Three domains exist above the Kingdoms Archae Bacteria Eukarya Monera Kingdom now obsolete

RNA Replication

Miller and Urey

Pasteur