Origin Of Life Earth formed 4.6 billion years ago When, and how did life originate? Life is believed to have begun 3.5 billion years ago How did the first life form come to exist? Spontaneous generation theory accepted until 1862 Biogenesis paradox If life comes from life how did the first life form evolve?

Even though life does not spontaneously generate today it must have done so at the beginning. Look to changes in the planet to uncover conditions that favor this spontaneous generation of life. What was the primitive environment of Earth like? Reducing, electron adding. atmosphere No electron hogging oxygen gas was present.

Oparin and Haldane: Reducing atmosphere + high energy levels contributed to spontaneous chemical evolution New Evidence suggests that not much of the environment was reducing Life may have begun in deep sea vents Some organic compounds may have come from space Once organic monomers were formed the next stage was….

Polymer Formation Protobionts - molecules surrounded my membrane - like structures. Liposomes, microspheres and coacervates are examples of protobionts that have been spontaneously created in labs. What is still missing? Nucleic acids

RNA! RNA has the following properties: Less complex than DNA Less stable than DNA Has phenotype, can fold into diverse shapes Short strands of RNA can replicate Ribozymes, show enzymes can be non-protein molecules

Found in diverse environments: Sedimentary rock petrified (stone) trees molds left in stone preserved organisms in amber preserved bodies in areas with little decomposition (frozen in ice, in acid…)

Relative Dating fossils are frozen in time Compare similar strata of rock to obtain a relative date Radiometric Dating (Absolute Dating) gives a more exact age for the fossil Uses radioactive isotope half-lives

Geological Time Scales are establisheGeological Time Scales are established Four Eras: Precambrian Paleozoic Mesozoic Cenozoic

Earth’s history explains geographical distribution of species Continental drift has influenced major evolutionary events 250 mya all land masses converged into Pangaea Drifting of continents helps explain: marsupials of Australia matching fossils in Brazil and West Africa

Evolve novel characteristic Novel characteristic opens an adaptive zone Animal evolution of hard body may have led to Cambrian explosion Mammals with unique novelties did not diversify until dinosaurs opened up the adaptive zone to them

Permian extinction - coincides with Pangaea Cretaceous extinction - loss of dinosaurs May have been caused by asteroid

Heterotrophs – obligate anaerobes Eukaryotes Chemoautotrophs Photoautotrophs Oxygen in atmosphere results in mass extinctions Which came first autotrophs or heterotrophs? Facultative aerobes survive Cellular Respiration evolves Eukaryotic organisms Multicellular organisms

Kingdom _______________

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SHOWS MOLECULES SMALLER THAN RNA CAN SELF-REPLICATE!

C 14 has a half-life of 5600 years. How many years will it take a sample that began with 8g of C 14 to have 2g left? Converting 8g to 4 g is one half life. Converting 4g to 2g is 2 half lives. Therefore it will take 2 half lives or 5600 x 2 = 11,200 years.