ECOL 182R 1st Edition Lecture 14 Outline of Last Lecture I Deuterostomes II Echinoderms A Key lineages III Chordates IV Vertebrates V Primates Outline of Current Lecture I Cosmology II Origins of Life III Exobiology A Life nearby IV Mass Extinctions A The Big Five B Recent future extinctions Current Lecture Cosmology 13 7 BYA billion years ago big bang happened 400 million years later first stars population III stars made of H and He only They were massive and short lived These stars cookied heavier elements by nuclear fusion Collapsed on their own weight and became supernovas then population II stars began Population II stars were more metal rich than III They had elements beyond H and He As pop II stars ran out of fuel they generated even more metals before becoming novas Then pop I stars metal rich Result from pop II stars exploding carbon and iron Everything above He resulted from the ash of exploded stars Life death of a massive star ending in a gamma ray burst Formation of the sun 5 BYA our sun a pop I star formed Age of earth is roughly 4 5 billion years Oldest material zircon crystals Heavy meteorite bombardment ends around 3 9 billion years ago Stable crust formed around this time First signatures of life 3 85 BYA is the suggestion of organic molecules contains carbon in rocks from Greenland 3 6 BYA we had signals of methane producing bacteria and hydrogen sulfide photosynthesis 3 5 BYA microfossils 2 5 BYA cyanobacteria starts forming oxygen via photosynthesis 2 2 BYA aerobic respiration Origins of life Haldane Oparin Miller Urey Minicells and hypercycles RNA world Metabolism based models Aleksandr Oparin Published Origins of Life Argued that a primeval soup or organic molecules could be created in an oxygen less atmosphere through sunlight Life self replicating chemical reactions arose in this soup Also said that this is now impossible because 1 the conditions found in early earth have changed 2 the presence of living organisms would immediately consume any products of such reactions J B S Haldane About the same time as Oparin Said that Earth s prebiotic oceans would have formed a hot dilute soup where organic compounds could have formed Said that living matter could evolve from self replicating but non living molecules Steps in the orgins of life Form complex organic molecules Self replicating systems Protein synthesis Put all these in the first cell Origins of complex organic molecules Nucleosynthesis in stars to form complex molecules Molecular clouds Very significant fractions of earth carbon came from comets to primitive Earth Model systems for prebiotic evolution The Miller Urey experiment Take glass cylinder and fill with stuff that we think is from early Earth spark in with gases from early Earth Precipitate them then something accumulates Showed that complex organic molecules were in there like amino acids Compartmentalization Fox s microspheres Sidney Fox showed that by heating certain proteins microspheres form spontaneously Under the right conditions microspheres bud new spheres Model system for compartmentalization critical step in the origin of life Catalytic RNAs Problem biological systems use complex proteins for their chemical reactions The first self replicating systems used RNA which can both cleave itself as well as polymerase itself One solution to the chicken vs egg problem Don t need proteins as RNA can act as an enzyme Tom Cech self cleaving RNA Carl Woese said the first earth may have been an RNA world Makes sense because DNA synthesis required RNA primer RNA not DNA is used in protein synthesis Reverse transcriptase RNA DNA Information storage Eigen Schuster Hypercycles By linking replication LOTS more info can be stably maintained in an early self replicating system EXOBIOLOGY Life Beyond Earth Also called astrobiology Models for the origin of life suggest that the ey for life as we know it is liquid water Search for life in our solar system and on other stars SETI Search for Extraterrestrial Intelligence Life nearby Europa 4th largest moon of Jupiter Mars Titan largest moon of saturn Enceladus 6th largest moon of saturn Europa Roughly the size of our moon Liquid water under ice tectonic activity and therefore possibility of hydrothermal vents Metallic core Life may exist around hydrothermal vents Uses chemical energy rather than light Mars Ice caps of carbon dioxide Evidence of significant past flows of liquid water billions of years ago What shook up Mars Allan Hills 84001 Meteorite from Mars found in Antarctica Suggestions of fossil life Other tests showed organic molecules Still highly debated if real or artifact Titan Really big Contains methane and hydrocarbons Lakes of liquid methane and hydrocarbons on the surface Cryovolcanoes vent water and ammonia from its core into the atmosphere Enceladus Liquid water under surface Cryovolcanoes Tectonic activity Planetary conditions for life sun like stars If it s too big shorter life and not enough time to evolve If it s too small not enough heat Liquid water or water ammonia mixtures Extrasolar planets are common Planets on other stars Gliese 581 red dwarf has four planets and is within the habitable zone Drake equation the number is 10 MASS EXTINCTIONS Have occurred throughout history when a large fraction goes extinct over a short period of time Fundamentally changed progression of life The Big Five Ordovician Silurian Late devonian Permian Triassic the great dying Cause unknown Siberian traps one of the largest volcanic events Allowed dinosaurs to take over Cretaceous Tertiary shut down the dinosaurs Probably a comet or asteroid More recent Quaternary extinction Climate change maybe Paul Martin U of A Killed off by arrival of early human hunters Toba Super volcano in Sumatra largest in last 25 MY Caused huge climate change Future death extinctions Gamma ray burst within 8 10 TLY from earth can be because by close binary stars when the companion stars fall into each other Nearby candidate is the star system Wolf Rayet 104 Rotational axis of system 16 degrees of earth direct target for a GRB jet Comet asteroid impact happened to Jupiter