Early Earth and the Origin of Life

Conditions on early Earth made the origin of life possible

-Earth formed about 4.6 billion years ago -Earth cooled about 3.9 billion years ago -The first atmosphere: thick water vapor various compounds released by volcanic eruptions nitrogen and its oxides, Carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide -Lightning, volcanic activity, and UV radiation were much more intense than today

Protocells

-Replication and metabolism are key properties of life and may have appeared together in protocells -Protocells may have formed from fluid-filled vesicles with a membrane-like structure -In water, lipids and other organic molecules can spontaneously form vesicles with a lipid bilayer -All organisms must be able to carry out both reproduction and energy processing (metabolism) and a metabolic source of building blocks may have appeared together in early protocells -abiotically produced vesicles can exhibit certain properties of life, including simple reproduction and metabolism, as well s the maintenance of an internal chemical environment different from that of their surroundings -abiotically produced vesicles can reproduce on their own and they increase in size without dilution of their contents -A vesicle self-replicating, catalytic RNA could grow and pass its RNA molecules to its "daughters," the "daughters" would be protocells

Self-replicating RNA

-The first genetic material was probably RNA -RNA molecules called ribozymes have been found to catalyze reactions ex: ribozymes can make complementary copies of short stretches of RNA RNA may have provided the template for DNA

Alkaline vents

-deep-sea vents -release water that has a high pH and is warm rather than hot, an environment that may have been more suitable for the origin of life

Hydrothermal vents

-hypothesis that organic compounds were first produced in deep sea hydrothermal vents -areas on the seafloor where heated water and minerals gush from eArth's smokers, release water so hot that organic compounds formed there may have been unstable

The first life may have evolved through four stages

1) Abiotic synthesis of small organic molecules, amino acids and nitrogenous bases 2) Joining of molecules into polymers, proteins and nucleic acids 3) packaging of molecules into "protocells" 4) Origin of self-replicating molecules that eventually made inheritance possible