History of life
I. Early Earth Conditions A. Time-line of earth formation 1. 4.6 BYA - sun and planets form 2. 4.6-3.9 BYA - meteoritic bombardment and volcanic activity create reducing atmosphere 3. By 3.9 BYA - reducing atmosphere (high in hydrogen content, no free oxygen, thick with water vapor) 4. 3.9 BYA onwards – first cells appear
II. How Did Life Start A. Steps necessary to evolve cells from inorganic precursors 1. Abiotic synthesis of simple organic molecules (monomers) a. PROBLEM: Early scientists assumed that organic molecules are formed only by organic life b. SOLUTION: inorganic chemistry found to create organic compounds 1. Miller/ Urey experiments 2. Hydrothermal vents 3. Extraterrestrial origins?
2. Monomers to polymers
a. PROBLEM: Complex polymers are generally created via organic enzymatic processes b. SOLUTION: Clay minerals facilitate polymer formation
3. Self-replicating hereditary material a. PROBLEM: DNA needs enzymes to replicate b. SOLUTION: RNA- the original unit of heredity 1. Self replicates 2. Self splices 3. Catalyzes 4. Possess a phenotype and genotype
4. Protobiont – aggregate of abiotically produced organic molecules suorrounded by membrane-like structure a. PROBLEM: Cell membranes associated w/ organic molecules derived from other organic cells b. SOLUTTION: Several "cell-like" structures form abiotically that can self-replicate and metabolize 1. Coacervates 2. Liposomes B. Protobiosphere 1. Multiple protobiont lineages may have independently evolved 2. Competition among lineages 3. Lineages evolve 4. Only one lineage remains today.
III. The history of Life A. First cells appear ~3.9 - 3.5 BYA
B. The first cells were chemoautotrophs 1. chemoautotrophs rely on chemosynthesis to produce glucose from chemicals, such as a. Sulfur (found at
II. How Did Life Start A. Steps necessary to evolve cells from inorganic precursors 1. Abiotic synthesis of simple organic molecules (monomers) a. PROBLEM: Early scientists assumed that organic molecules are formed only by organic life b. SOLUTION: inorganic chemistry found to create organic compounds 1. Miller/ Urey experiments 2. Hydrothermal vents 3. Extraterrestrial origins?
2. Monomers to polymers
a. PROBLEM: Complex polymers are generally created via organic enzymatic processes b. SOLUTION: Clay minerals facilitate polymer formation
3. Self-replicating hereditary material a. PROBLEM: DNA needs enzymes to replicate b. SOLUTION: RNA- the original unit of heredity 1. Self replicates 2. Self splices 3. Catalyzes 4. Possess a phenotype and genotype
4. Protobiont – aggregate of abiotically produced organic molecules suorrounded by membrane-like structure a. PROBLEM: Cell membranes associated w/ organic molecules derived from other organic cells b. SOLUTTION: Several "cell-like" structures form abiotically that can self-replicate and metabolize 1. Coacervates 2. Liposomes B. Protobiosphere 1. Multiple protobiont lineages may have independently evolved 2. Competition among lineages 3. Lineages evolve 4. Only one lineage remains today.
III. The history of Life A. First cells appear ~3.9 - 3.5 BYA
B. The first cells were chemoautotrophs 1. chemoautotrophs rely on chemosynthesis to produce glucose from chemicals, such as a. Sulfur (found at