Origin of Life prebiotic before life autocatalysis a reaction in which the products of the reaction result in an increase in the rate of product formation
Age of Universe estimated 13.798±0.037 billion years Age of solar system 4.6 billion years Prebiotic atmosphere - mostly methane, carbon dioxide, ammonia, hydrogen, nitrogen and water - virtually no free oxygen
Stanley Miller and Harold Urey s 1953 flask discharge experiment sparking (to simulate lightning) of water and simulated prebiotic atmosphere, i.e., methane, ammonia, and either hydrogen or nitrogen spontaneously produces aldehydes and hydrogen cyanide which react to form aminonitrile which reacts with water to form the amino acid alanine or with formaldehyde and water to form glycine
flask discharge end products (within a few days) all of the 20 (and more) amino acids found in life forms on earth the building blocks of life this could have filled the world's oceans with amino acids in concentrations to 10-4 M in only 10 million years the blink of an eye in geological time also produced: nucleotide purines and pyrimidines ribose sugar but these do not spontaneously combine to form deoxyribonucleotides or ribonucleotides
Why RNA was probably the first genetic material ATP and GTP are used as energy sources by all living organisms its components (i.e., nucleotide bases and ribose sugar; not RNA itself) are formed spontaneously in flask discharge experiments it has both genotypic and phenotypic properties (unlike DNA or amino acids which do only one or the other) genotypic: it self replicates with sequence fidelity (autocatalytic); it is the genetic material of many viruses phenotypic: it folds to produce secondary structure with protein-like functions, e.g., ribozymes, ribosomes, self polymerization, self splicing it has sequence-specific affinity for amino acids, i.e., translation transfer RNAs and ribosomal RNAs are synapomorphies of all living organisms
but did life begin on earth? carbonaceous chondrite a type of meteorite that includes water, carbon, hydrocarbons, and amino acids (including some that do not occur in organisms on earth) Panspermia hypothesis extraterrestrial origin of life bacteria have survived extraterrestrial conditions on US space flights
Geology - the study of earth and rocks types of rocks igneous from molten magma metamorphic from deformed sedimentary rocks sedimentary the type of rock that often preserves fossils stratigraphy the study of sedimentary layers superposition the notion that younger strata rest on top of older ones (barring deformation), introduces the concept of relative dating
relative measures of geological time superposition, indicator fossils, magnetic reversals absolute measure of geological time radioisotopic decay (probablistic) different elements for different time intervals based on half-life 235 Ur 207 Pb - 0.7 billion year half-life only good for dating inorganic rocks 40 K 40 Ar - 8.4 billion year half-life only good for dating really old inorganic rocks 14 C 12 N - 5730 years only good for dating quite recently living things
Review of Plate Tectonics island chain Distilling of lighter silicates hotspot Subduction zone at continental plate-ocean plate boundary
Seismic Activity
vectors and rates of plate movement
fossil record of life on earth all cellular life on earth believed to have a common origin the evidence comes from the same genes that are shared by ALL living things Phanerozoic 600 million years to present; the period of time during which fossils of organisms with hard body parts are preserved; Once thought to be the complete fossil record In fact, fossil microbes at least ~3.5 billion years old
Eons Hadeon 4.6 to 4 billion years ago condensation of earth and moon frequent bombardment by asteroids turnover of early crust Archean 4 to 2.5 billion years ago formation of most continental crust origin and proliferation of anaerobic cyanobacteria Proterozoic 2.5 billion to 550-500 million years ago plate tectonics in action evidence of supercontinent ( Rodinia ) build-up of atmospheric free oxygen ends with protracted Ediacaran transition to Cambrian soft-bodied multicellular plants and animals at least by Ediacaran Phanerozoic 550-500 million years ago to present proliferation of hard bodied multicellular organisms
stromatolites - precipitated by blue green algae (cyanobacteria)
Sectioned stromatolites
fossil cyanobacteria ~3.5 billion years old
Newly discovered in 2017 nanotubules of possible bacterial origin between 3.77-4.22 billion years old, just 340 million years after the formation of the planet, Nuvvuagittuq Formation CA
Xiao, Zhang,& Knoll (1998) Three-dimensional preservation of algae and animal embryos in a Neoproterozoic phosphorite. Nature. 391: 553-558.
cleavage
Precambrian Embryos (and/or colonial protists) Neoproterozoic (570 +20 MY) Doushantuo Formation China
Precambrian multicellular algae Neoproterozoic (570 +20 MY) Doushantuo Formation, China living Porphyra algae
Dickinsonia costata Ediacaran (late pre-cambrian 635-542MY) Australia (soft-bodied invertebrate, lichen or colonial microbe?)
The Phanerozoic Eon Eras Periods comments Paleozoic 541-252 MYA Pangean supercontinent Cambrian Ordovician Silurian Devonian Carboniferous Permian ends with first great extinction Mesozoic 252-66.5 MYA ( Age of Reptiles ) Laurasia and Gondwana supercontinents separated by equatorial Tethys Sea Triassic Jurassic Cretaceous ends with second great extinction Cenozoic 66.5 MYA-present ( Age of Mammals ) modern continents Paleogene Neogene
Era Periods comments Paleozoic 541-252 MYA Cambrian Ordovician Silurian Devonian Carboniferous Permian Pangean supercontinent first animals with hard body parts most invertebrate Phyla present brachiopods and cephalopods dominant all animals marine first land plants first cephalochordates and agnathans extensive continental seaways jawless fish flourish first jawed fishes land arthropods all fish present first amphibians first winged insects tropical/subtropical, wet lobe finned fishes dominant first reptiles breakup of Pangea continental elevation cooler ends with first great extinction
Era Periods comments Mesozoic 252-66.5 MYA ( Age of Reptiles ) Laurasia and Gondwana supercontinents separated by equatorial Tethys sea hotter and arid Triassic Jurassic Cretaceous Gymnosperms dominant first mammal-like reptiles first dinosaurs formation of Atlantic Ocean begins development of continental seaways first birds Angiosperms ends with second great extinction
Chicxulub Crater from http://www.atlasobscura.com/places/chicxulub-crater
Chicxulub Meteor impact-generated wildfires Daniel D. Durda, NASA/UA Space Imagery Center's Impact Cratering Series http://www.lpi.usra.edu/science/kring/epo_web/impact_cratering/enviropages/wildfires.html
Era Periods Epochs comments Cenozoic 66.5 MYA - present ( Age of Mammals ) Paleogene Paleocene Archaic mammals Eocene Oligocene modern mammals and birds first anthropoids Antarctic circumpolar current latitudinal thermal stratification global cooling first apes Miocene Pliocene first hominids Neogene Pleistocene first humans Holocene
Ordovician Echinoderms sessile crinoid (above) free-swimming cystoids
Ostracoderms: the earliest jawless fishes Ordovician-Silurian
Devonian Ostracoderms from Wyoming
Ostracoderm head armor
Ostracoderm nervous system pharynx
Placoderms: earliest jawed fishes Silurian-Devonian
Placoderm head armor Paired appendages Bothriolepis Devonian Wyoming
Dunkleosteus (arthrodire placoderm) Devonian apex predator
Sarcopterygii: fleshy finned fishes Devonian-Carboniferous Dipnoi: lungfishes Crossopterygii: coelocanths