Origin of Life

Universe formed 15 billion years ago (Big Bang) Galaxies formed from stars, dust and gas Earth formed 4.6 billion years ago

Earth 3.5 bya

Suns energy stripped away 1 st atmosphere 2 nd atmosphere formed from volcanic outgassing Primitive atmosphere: CO 2, water vapor, lesser amts of CO, N 2, H 2, HCl, and traces of NH 3 and CH 4 (3.5 bya)

O 2 came in bya Autotrophic Organisms: photosynthesis Another environmental change Result in evolution

The sum total of the chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material, etc. Anabolism- build up of complex molecules Catabolism- break down of complex molecules Metabolism

Autotrophs –Organisms that get their energy by making their own food (like plants) –Plants capture energy from the sun, use water and carbon dioxide to make sugars and starches Heterotrophs –Organisms that take in food to meet their energy needs –Animals must consume autotrophs (plants), and other heterotrophs to meet their energy needs

Earth’s Atmosphere

Oxygen Evidence for O 2 production:  Banded Iron Formations (BIF)  BIF found in ocean sediments red bands are high in Fe 2 O 3 and Fe 3 O 4 (red bands)- forms when reduced iron reacts with O 2

Photosynthesis 6H 2 O + 6CO 2 + light  C 6 H 12 O 6 + 6O 2

“Oxygen revolution” Time (billions of years ago) , Atmospheric O 2 (percent of present-day levels; log scale) Oxygen

Evolution of Ozone Accumulation of free O 2 in the atm also led to the accumulation of ozone –Ozone important for blocking incoming UV radiation Even small amounts of atm O 2 leads to enough ozone to provide some protection against UV –Partial screen likely to have formed ~ 1.9 bybp –Presence of this UV filter allowed life to move out of the oceans and onto land –Consistent with the timing of evolution of eukaryotes and higher plants

0.5 billion years ago Atmosphere O 2 to 1% current Compare to present: 78% N 2, 21% O 2, 0.04% CO 2, + trace gasses Relatively small, most single cell Start of multicellularity Increase in cell complexity

Formation of Earth’s Oceans (4 bybp): Rain Condensation Off gassing of water vapor from volcano

Life began~ 3.5 bya Organic molecules (C H O N P S) swimming in shallow seas Stage 1: Abiotic synthesis of organic molecules such as proteins, amino acids and nucleotides

Stage 2: joining of small molecules (monomers) into large molecules

Stage 3: origin of self-replicating molecules that eventually made inheritance possible

Stage 4: packaging these molecules into pre-cells, droplets of molecules with membranes that maintained an internal chemistry

Thomas Huxley- Search for origin of life Wyville Thompson: HMS Challenger ( ) found it was actually diatomacous ooze reacting with seawater and ethyl alcohol Bathybias heckali- primordial ooze

Miller and Urey’s Experiment ELECTRICITY!!! Organic molecules like amino acids

Produced: 20 amino acids Several sugars Lipids Purine and pyrimidine bases (found in DNA, RNA & ATP)

END.

RNA world The first genetic material was probably self- replicating, catalytic RNA not DNA; In “RNA world”, RNA could have provided the template on which DNA was assembled Once DNA appeared “RNA world” gave way to “DNA world” The first organisms were not photosynthetic; they were probably heterotrophic

The RNA world theory says that RNA both stored and catalysed reactions that reproduced genetic information in early evolution.

Protobionts, collections of abiotically produced molecules surrounded by a membrane-like structures Liposomes can form when lipids or other organic molecules are added to water. - Have a bilayer - Can undergo osmosis - Can “reproduce”

Protocell (Protobiont) Fatty acid membrane with ribozymes inside

Oxygen Earliest Evidences: oldest fossils  Oldest photosynthetic microbes B.Y. - Bacterium-like - Unicellular - Evidence for breakdown products of photosynthesis  Cyanobacteria, 3.5 B.Y.  Stomatolites, B.Y.

Three-domain system ExtremophilesProkaryotesEukaryotes Look at how this evolution happened!

chemosynthetic bacteria (extremophiles) Chemosynthesis: H 2 S + C02 CH S +3H 2 0 Stromatolites (bacteria & cyanobacteria) Oldest fossils found in western Australia and southern Africa ~ 3.5 byo Photosynthesis: 6H 2 O + 6CO 2 + nutrients + light energy C 6 H 12 O 6 + 6O 2

Cellular Respiration C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + energy

Stromatolites from Shark’s Bay Australia mostly cyano

Early prokaryotes may have arisen near hydrothermal vents Hydrothermal vents are rich in sulphur and iron-containing compounds needed for ATP synthesis. Temperatures can reach 120 C.

Hot springs in Yellowstone National Park – pigmented bacterial mats