Precambrian History PDF

AARHUS UNIVERSITY LIFE THROUGH EARTH’S HISTORY AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE WHAT TO EXPECT IN THIS UNIT - History of life on Earth - Earth processes th...

AARHUS UNIVERSITY LIFE THROUGH EARTH’S HISTORY AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE WHAT TO EXPECT IN THIS UNIT - History of life on Earth - Earth processes that led to life and life that led to Earth processes - An understanding of how the Earth, climate, and life are intertwined and important for holistic understanding - An understanding of timescale - Bold = potentially new vocabulary AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE GEOLOGIC TIME ACTIVITY - Get in a group of 4 - Get to work recording geologic and climate events that you discussed with Mads - 50 meters = 5 billion years… - Make the inside of the paper roll 5 Ga and the outside today - We’ll get back to this at the end of Life through Earth’s History AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE LIFE THROUGH EARTH’S HISTORY: PRECAMBRIAN AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  EARTH’S FORMATION In the first AARHUS 50-100 million years after Earth’s formation… PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY D EP ARTME NT OF GE OS CI ENCE … there was a lot of heat, volcanic activity, and radiative decay ASSISTANT PROFESSOR  THE HADEAN The Hadean AARHUS saw a lot of change… PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY …with the Moon forming, cooling, and the slow formation of continental crust D EP ARTME NT OF GE OS CI ENCE ASSISTANT PROFESSOR  THE LATE HEAVY BOMBARDMENT Because the atmosphere was so thin, meteorites and asteroids bombarded the planet. Today, AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY we’re protected from these because they burn up upon entering our atmosphere. D EP ARTME NT OF GE OS CI ENCE ASSISTANT PROFESSOR ARCHEAN VOLCANISM - Ocean was spotted with volcanos - Strong volcanic activity in the early Precambrian led to a lot of gas emission - Mostly emitted CO2 and H2O - Toxic atmosphere also contained methane, ammonia, H2, N2, and SO2 AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE HYDROSPHERE - When Earth cooled enough below boiling point, liquid rain fell out of the atmosphere - Sources of surface water include: - Outgassing from Earth’s interior - Bombardment by meteorites and icy comets AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE FAINT YOUNG SUN PARADOX - Models show the Sun was ~75% weaker - This would make Earth 25ºC lower… freezing all water - But there is evidence for liquid water going back 4.4 Ga This is the Faint Young Sun Paradox AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE FAINT YOUNG SUN PARADOX Two explanations: 1. Greenhouse effect - CO2, methane, water vapor trapped solar radiation AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE FAINT YOUNG SUN PARADOX Two explanations: 1. Greenhouse effect - CO2, methane, water vapor trapped solar radiation and/or 2. Earth had a lower albedo - Oceans must have covered even more of Earth than now - Water absorbs more sunlight than land, keeping Earth warm AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE FAINT YOUNG SUN PARADOX Two explanations: 1. Greenhouse effect - CO2, methane, water vapor trapped solar radiation and/or 2. Earth had a lower albedo - Oceans must have covered even more of Earth than now - Water absorbs more sunlight than land, keeping Earth warm AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE TODAY’S ATMOSPHERE - Protects us from radiation - Protects us from meteorites - Keeps us a stable temperature - Oxygen lets us breathe and turn food into energy AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE ARCHEAN ATMOSPHERE - Approximately 80% CO2, 10% H2, 10% N2, some methane … toxic - Very thin AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE WHAT IS LIFE? - Various definitions! - But from a biology and chemistry, it is something made of organic molecules that can respond to stimuli - Carbon is the key to life because of its atomic capability of forming bonds in a variety of ways AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE WHAT IS LIFE? - Building blocks of life - Carbohydrates (sugars), nucleic acids, proteins, and lipids AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE EVOLUTION The change of heritable characteristics or biological populations over successive generations AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE TREE OF LIFE AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE PHYLOGENETIC TREE - Cladogram - Diagram that focuses on showing points that different organisms radiated from common ancestors - Positions are based on DNA AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  CELLS OF THE 5 KINGDOMS Five kingdoms AARHUS UNIVERSITY differ in: 1. cell type, 2. single vs multi cells, 3. energy acquisition D EP ARTME NT OF GE OS CI ENCE PLANET EARTH 2024 RACHEL LUPIEN ASSISTANT PROFESSOR 1. PROKARYOTE VS EUKARYOTE CELLS - All cells have plasma membrane, ribosomes, cytoplasm, DNA - Euk. cells are larger, have membrane-bound nuclei with chromosomes - Many euk. are multicellular, aerobic, and reproduce sexually = diversity AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  2. SINGLE VS MULTICELLULAR ORGANISMS Single cell organisms are organisms with one cell, while primitive multicellular organisms have multiple cells of the same type and complex multicellular organisms have different types of cells to perform specialized functions. AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  3. AUTOTROPHS VS HETEROTROPHS Autotrophs obtain their energy from the sun or chemical sources… AARHUS UNIVERSITY … so, the first life on Earth must have been a prokaryote, single-cell autotroph. PLANET EARTH 2024 RACHEL LUPIEN ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE HOW DID LIFE BEGIN? - Must have been a prokaryote, single-cell autotroph - Autotrophs need an energy source, and photosynthesis had not yet existed (we’ll come back to this) - So the very first life on Earth may have used chemosynthesis - This is the process where food is generated using chemicals, typically in the absence of sunlight AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE HOW DID LIFE BEGIN? - Must have been a prokaryote, single-cell autotroph - Autotrophs need an energy source, and photosynthesis had not yet existed (we’ll come back to this) - So the very first life on Earth may have used chemosynthesis - This is the process where food is generated using chemicals, typically in the absence of sunlight - At hydrothermal vents along mid-ocean ridges, “black smokers” emit ion-charged solutions that build up as chimneys - And the structure and chemistry of the hollow chimneys generate a weak electrical charge that gave the first life energy AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE FIRST EVIDENCE OF LIFE 1. Chemical fossils - Biomarkers are molecular remnants of metabolism, the processes that organisms use to harvest energy 2. Isotopic signatures - More depleted carbon isotope signatures are indicative of life, which preferentially uses 12C over 13C during metabolic processes 3. Fossil forms - Depending on the depositional environment, fossils of bacteria and archaea can actually be preserved AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  FIRST FOSSILS OF LIFE – 3.2 GA Although there is earlier biomarker and isotope evidence (from ~4.1 Ga), some of the very first evidence we have of life are from AARHUS fossils of bacteria or archaea preserved in chert from South Africa. UNIVERSITY PLANET EARTH 2024 RACHEL LUPIEN ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE HOW WAS OXYGEN BEING PRODUCED? - The Precambrian atmosphere had little or no free oxygen - Free oxygen is O2, not O locked up in H2O, CO2, etc. - But we know that Oxygen rose to create the atmosphere we have today for aerobic life AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE HOW WAS OXYGEN BEING PRODUCED? - The Precambrian atmosphere had little or no free oxygen - Free oxygen is O2, not O locked up in H2O, CO2, etc. - But we know that Oxygen rose to create the atmosphere we have today for aerobic life - So how could it have been produced? 1. Photochemical Oxidation 2. Photosynthesis AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE 1. PHOTOCHEMICAL OXIDATION - Incoming UV radiation disrupted H2O molecules - Produces free O2 and H that escaped to space - Some O2 converts to ozone… we’ll come back to this AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE 2. PHOTOSYNTHESIS - Aerobic autotrophs use the energy from the Sun along with the readily available CO2 and H2O - Generate building blocks of life and O2 - But the ability to photosynthesize had to evolve AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  STROMATOLITES – 3.5 GA Stromatolites are produced by cyanobacteria (formerly known as blue-green algae – NOT algae)… AARHUS UNIVERSITY … and cyanobacteria photosynthesized to make free oxygen! PLANET EARTH 2024 RACHEL LUPIEN ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE STROMATOLITES – 3.5 GA - These bacterial mats are made up of bacteria and archaea colonies - They trap sediment which sticks to layers of cells that causes them to die - This cycle causes compaction and layer formation that we can see in the geologic record AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE FIRST MASS EXTINCTION: 2.3 GA - Who remembers what happened around 2.3 Ga? AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  GREAT OXYGENATION EVENT: 2.5-2.3 GA Cyanobacteria contributed to oxygenic photosynthesis for up to 1 billion years before we have any evidence for a Great Oxygenation Event starting at 2.5 Ga… AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY … Transition from Archaean to Proterozoic, meaning “earlier life” D EP ARTME NT OF GE OS CI ENCE ASSISTANT PROFESSOR  BANDED IRON FORMATIONS: 2.5-1.8 GA BIFs are produced under water where iron is being oxidized to precipitate out and form rock… AARHUS UNIVERSITY … 90% of the BIFs on Earth were generated in a relatively short period of time. PLANET EARTH 2024 RACHEL LUPIEN ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE REDOX REACTIONS Redox = reduction + oxidation = transfer of electrons - Ferrous (Fe2+ reduced) - Ferric (Fe3+, oxidized iron oxides like hematite and magnetite) Fe2+ + O2 + H2O → Fe3+2O3 (aqueous) (gas) (liquid) (solid) AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  GREAT OXYGENATION EVENT: 2.5-2.3 GA Around 2.3 Ga, there was a “sudden” increase in atmospheric oxygen… AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY …Once iron had precipitated and the ocean became saturated with O2… D EP ARTME NT OF GE OS CI ENCE ASSISTANT PROFESSOR  RED BEDS: 2.3 GA Red beds indicate that there was now enough free oxygen in the atmosphere to start precipitating Iron Oxides on the continent UNIVERSITY~2.3 Ga. AARHUS PLANET EARTH 2024 RACHEL LUPIEN ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE THE PROTEROZOIC - Free O2, which also means ozone (O3) - The Ozone Layer provides a lot of protection from UV radiation - Meaning land was then habitable - Going into the Proterozoic, most life was Prokaryotic… AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE ANCIENT FOSSILS: OLDEST EUKARYOTES AARHUS Oldest known eukaryote (1.2 Ga) Oldest macrofossil (2.1 Ga, algae) PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE ENDOSYMBIOSIS IN EUKARYOTES - One organism absorbs another – living together - 2.0 Ga – first occurrence - Aerobic bacteria become mitochondria in all eukaryotes - Photosynthetic bacteria (Guess who!) become chloroplasts in plants AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE PROTEROZOIC - Animals finally appeared in the Neoproterozoic at the end of the Precambrian around 800, 700, 600 Ma… - First evidence for animals are worm burrows in sediment - We know this from both fossils and trace fossils AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  THE EDIACARAN FAUNA The Ediacaran AARHUS was the last period of the whole Precambrian… PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY … and named for the region in Australia where fossils were found and is known for a general group of fauna. D EP ARTME NT OF GE OS CI ENCE ASSISTANT PROFESSOR THE EDIACARAN FAUNA - Found on all continents except Antarctica - Consists primarily of multicellular soft-bodied organisms - Trace fossils: impressions, burrows, trails - Discussed generally, because not much is known AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  THE EDIACARAN ENVIRONMENT Other kinds AARHUSof fossils from the Neoproterozoic include jellyfish-like impressions, burrows (horizontal) and maybe PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR fossils from worms, and several animals with skeletons, or at least partial skeletons. D EP ARTME NT OF GE OS CI ENCE CAMBRIAN EXPLOSION: 541 MA AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE PRECAMBRIAN LIFE 4.6 Ga: Earth formed 4.1 Ga: First anaerobic prokaryote single-cell life 3.5 Ga: First photosynthetic life = stromatolites 2.5 Ga: O2 production = BIFs appear 2.5-2.3 Ga: Great Oxygenation Event 2.3 Ga: O2 in atmosphere = red beds appear 2.0 Ga: First multicellular eukaryote organisms ~700-550 Ma: Ediacaran fauna, first animals AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE  Early Earth 34 2 1 No free O2 Free O2 AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE HOMEWORK FOR THURSDAY - Answer questions on Precambrian Life on Brightspace on your own - In class, we’ll then pair up and compare answers - And address any questions AARHUS PLANET EARTH 2024 RACHEL LUPIEN UNIVERSITY ASSISTANT PROFESSOR D EP ARTME NT OF GE OS CI ENCE AARHUS UNIVERSITY