Early Earth and the Origin of Life Logical Progression Possible Scenarios Supporting Data Problems Abiotic Synthesis of Monomers Reducing Atmosphere Deep SeaOuter SpaceMiller- Urey Experi ment Imbedded organic compounds found in vents Organics found in meteors and comets Abiotic Synthesis of Polymers Concentrated hot monomers form polymers as evaporation and cooling takes place Process fits all scenarios above but differs in location Minerals, clay, “pyrite”, iron & nickel sulfides could be used as catalysts Monomers form polymers when dripped on hot sand, rock, or clay Polymers have been found embedded in deep sea vents Origin of Genetic Information “It’s an RNA world” RNA was the first genetic molecule(genotype) that functioned also as an enzyme (phenotype)genetic molecule(genotype Natural selection picked the best RNA molecules as it replicated and “metabolized” available monomers RNA-amino acid interaction by molecular cooperationmolecular cooperation Short sequences of RNA can replicate with zinc as catalyst RNA can act enzyme like (ribozyme) RNA types allow natural selection Formation of Protobionts membrane bound “cells” with some properties of life Abioticly produced molecules interact to maintain a constant internal environment showing irritability and metabolism Protobionts called Liposomes form from lipid, COH, and protein that have:Liposomes 1. Lipid bilayer that shows osmosis 2. Voltage across membrane (membrane potential) 3. Engulf and split 4. Simple metabolism A.A.  Protein Sugar  Starch Nucleotides  DNA C+H+N+O  Amino acids simple sugars lipids H20,H, CH4, NH3 + Energy  amino acids. Nucleotides sugars Vents used iron and sulfur and hot water to build from CO2 and ammonia Comets, meteors, space dust showered earth with organic molecules 3.5 bya fossilized stromatolites (layered clay rock) formed by 1 st prokaryotes

Timeline of Key Life Events on Earth 4.6 bya Present Earth forms Prokaryotes appear Prokaryotes photosynthesize; O 2 revolution by cyanobacteria, kills most prokaryotes, leads to cell respiration O 2 revolution Eukaryotes appear!!! Endosymbiont theory Endosymbiont theory – mitochondria and plastids are former small prokaryotes that lived in larger cells Evidence: Multicellular organisms appear (algae & soft- bodied animals in water) Cambrian Explosion! Most phyla form Colonization of land ~adaptations to combat desiccation & gravity 1. Inner membrane is like those of prokaryotes 2. They replicate like prokaryotes 3. Have cell machinery (i.e. ribosomes) like prokaryotes 4. Similar size, have circular DNA, & RNA sequences like pros

Amino Acids and other organic compounds found in sample Miller and Urey Experiment 1953 (testing Oparin and Haldane’s idea) Reducing Atmosphere Energy source (Lightning) Slide 1

A Model for Gene Replication RNA WAS THE ORIGINAL GENETIC MATERIAL

Slide 1 “Life-Like” Activities of a Liposome Simple ReproductionSimple Metabolism

Slide 1 Cooperation of RNA and Proteins

Slide 1 Primitive Earth: Reducing Atmosphere?

Slide 1

Clock Analogy for Key Events in Earth’s History Slide 2

Rise of Earth’s Atmospheric Oxygen Slide 2