1. the development of the biosphere

stromatolites and black-siliceous mudstones contain high levels of carbon/other evidence of organisms 3.8 million years ago. in order for organic molecules (DNA and sugars) to form, amino acids must first arrive on Earth. multiple theories surrounding this.

Urey and Miller’s experiments (1950)

Oparin-Haldane (1920) suggested that amino acids could have slowly spontaneously reacted using UV/lightning radiation (oceans as a medium for amino acids to exist, lack of free oxygen prevent from breaking down). used gases in Earth’s early atmosphere: Methane (CH4), Water Vapour (H20), Ammonia (NH3), Hydryogen (H2), Carbon Dioxide (CO2), a spark and a heating/condensing system. by the end of the week water had turned red and contained amino acids including alanine. by restarting with differing composition of gases/carbonates in ocean nearly all of 20 amino acids were formed. transformed speculation into legitimate field of science.

communities around black smokers

investigations found that marine ecosystems of tube worms and mussels feeding on chemosynthetic bacteria around underwater hydrothermal vents (formed at divergent boundaries, carry hot water and sulphides from inside Earth) .these bacteria convert hydrogen sulfide and carbon dioxide into carbohydrates. aditionally large amounts of methane and ammonia formed around vents contain chemical necessary for organic molecules (high temperatures drive reaction, clay particles catalyse). however more evidence needed.

• black smokers: 350 celcius, iron and copper sulphides

• white smokers: 250, calcium and barium sulfates

• alkaline vents: 60, hydrogen, sulfur, silica, calcium, magnesium, nickel, iron, carbonate ions

panspermia

chemical origin could form on carbonaceous chondrite meteors and travelled distances to Earth. eg. murchinson meteorite (fell in Aus) contains number of organic materials (organic polymers, organic acids, hydrocarbons, amino acids, urea etc). same with meteors from Kuiper belt. very short (200 million years ish) between conditions stabilising and formation of life, most likely with panspermia.

geological time scale

each marked by major fossil/fossil assemblage.

eon> era> period

evidence for development of photosynthetic life

microspheres (fat-like membrane around chemicals, non-living)→ prokaryotic bacteria (chemosynthesis = changing inorganic chemicals into food, 3.5 bya)

development of photosynthetic (the process by which plants and some bacteria use sunlight to make their own food) bacteria.

cyanobacteria: bluegreen algae. first appeared in fossil records almost 3.5 billion years ago. perform photosynthesis

stromatolites:

• accumulation of sediment (eg chert) trapped in filament of cyanobacteria

• self-contained microbial ecosystens of prokaryotic, photosynthetic producers and consumers

• cyanobacteria convert CO2 and water into carbohydrates and O2 (using sunlight), purple bacteria chemosythesise CO2 and H2S into carbohydrates and O2. consumer microbes reprocess and metabolise waste. this allows to survive range of conditions

• produce fossils with distinct laminations

• found across the world, many of the oldest in Australia

evidence:

• fossilised stromatolites in chert, WA, 3.43

evidence for origin of multicellular life and impact on ecosystems

• sulfide rich oceans during early/middle proterozoic limited amounts of oxygen, drove biochemistry. created the multi-cellular ‘bangiomorpha’ 1200million years ago

• difficult to track fossil record due to lack of hard shells etc

Ediacaran Fauna (635-542 mya)

• correlates to time when snowball Earth was thawing

• soft bodied organisms, milimetres to metres across

• ranged in complexity from jelly-like blobs (Kimbrella), which formed cast fossils from sand to feathered fronds, to worms (tribrichadium)

• primarily lived in shallow marine environments

• little evidence of predation

• likely disappeared due to: rise of predators/more specialised feeding modes, development of biomineralisation allowing skeletons, increased complexity of ecosystem and organism interactions, increase in depth/intensity of burrowing animals leading to destruction of microbial matgrounds

• found in ediacaran hills south australia

Cambrian Fauna (541-485 mya)

• by about 540 mya, all 34 phyla of life today are represented. diversity of life exploded.

• animals increased in size, complexity and developed hard parts/skeletons

• factors for cambrian explosion: supercontinent Pannotia broke into Laurasia and Gondwana, global temperature rose 22 degrees, ice sheets receeded and oceanlevels rose causing change in ocean chemistry, ozone layer formed, more oxygen for development of active organisms

• predators were main driving force of evolution: shells provide protection, use of burrows, more sophisticated eyes, protective spikes

• trilobite index fossil, disappeared in permian

• burgess shale western canada

conquest of land by plants and animals

only took about 50 million years for organisms to move onto land. there were a number of pressures that needed to be overcome for organisms to survive on land:

• threat of desiccation due to lack of water: shelled eggs and internal watery environment

• absence of buoyancy due to lack of water: skeletons(vertebrate), cellulose, root systems

• greater range of temperature: behavioural (return to water occasionally), mechanisms such as sweating/shivering

• different environment for food: plants now have more CO2, different minerals. early animals carnivorous

• differing gaseous exchange: lungs and stomata

• increase in predators (as seen in Ediacaran): structures such as shells, behaviours, hard-shelled eggs etc

plants: earliest land plants emerge during ordovician, earliest vascular plants (cooksonia) occur in rocks in late silurian. vascular plants had stomata and waxy cuticle, but no true roots or leaves. true flowering angiosperms wouldn’t appear until the cretaceous.

insects: arthropods appeared in the Silurian period. small, lightweight, chitin shell, primitive respiritive/vascular systems. open vascular system

vertebrates:

eg. labyrinthodont

non-vertebrate fish → vertebrate fish → jawed fish → tetrapods (devonian) → amphibians (could live on land, but still aquatically dependant)→ reptiles carboniferous (water-tight skin and eggs) → dinosaurs, mammals (more capable brain, faster metabolism, placental uterus) and birds jurassic

appeared in middle devonian. vertebrate fish became dominant, however took 15 million years to evolve first tetrapods that actually walked on land. lobe fins became tetrapods eg. Acanthostega, that had four feet, could occasionally clamber ashore,

animals land → sea: acanthostega, ichthyostega, tiktaalik

2. changes in the geosphere, atmosphere and hydrosphere

effect of photosynthesisng cyanobacteria

atmosphere: cyanobacteria photosynthesised CO2, produced O2 which was released into oceans and then atmosphere. O2 started to accumulate, creating ozone layer. photoclonical reactions formed ozone layer, most concentrated in stratosphere. snowball earth. removal of CO2 created global cooling. O2 reacted with methane in atmosphere, accelerating cooling. caused multiple ice ages eg. Huronian glaciation (2.4-2.1 bya)

hydrosphere: O2 reacts with iron ions in early oceans to form insoluble iron oxides.

geosphere: O2 react with iron ions, precipitate, settle at bottom. O2/iron is depleted, silica sediment is precipitated. more iron leaches into ocean from land, more O2 is produced. cycle repeat for 500 million years, because this is depth of BIFs. after this, atmosphere was oxidised instead. took another 200 million years to stabilise.

3. plate tectonic supercycle

process has repeated at least 6 times, evidence includes Appalachian mountains in North America and Caledonian mountains in North-West Europe. separated due to seafloor spreading.

first cratonic landmasses likely formed during the Archean Eon.

craton:stable masses of ancients continental crust, forming the nucleus of a continent

continent: made up of several cratons

Here's a mnemonic for the letters E J M D T RS:

Every Jolly Monkey Dances To Rhythmic Sounds.

You can use this sentence to remember the letters in order: E J M D T RS.

effect of supercycle including climate and evolution

break up = warmer, large igneous provinces, weathering decrease as sea level rise

amalgamate = cool, orogeny and weathering of rocks draw in CO2 eg. carbonates, thermally uplifted supercontinent

linking plate tectonic supercyle to Proterzoic oxygenation event

as continents drift apart, more CO2 is released to the environment (outgassing, basaltic magma etc), forming more carbonic acid rain. This acidic rain weathers terrestrial rock, increasing flow of phosphorus and other nutrients to oceans, including to photosynthetic bacteria, thus influencing oxygen produced.

4. fossil formation and stratigraphy

revision: laws of stratigraphy

• uniformitarianism: proccesses that alter Earth’s crust are the same that occurred millions of years ago, and produce the same result. can see result in fossil record and assume process eg. ripple stream marks

• original horizontality: sediment is deposited horizontally and will remain in layers until a force alters this

• superposition: oldest at bottom, youngest at top

• cross cutting relationships: a rock must already be in place to be cut by a fault, igneous intrusion or erosion ie. the rock cutting is younger

• original continuity : sediment is originally deposited in a continuous horizontal sheet until it meets some obstacle

fossils are the preserved remains and impressions of ancient biological organisms.

• sediment deposits (common in oceans)

• amber

• tar pits (natural tar covered in thin layer of water)

• cave systems

can occur by replacement: organic material replaced by inorganic materials such as quartz (silicification), clacite (calcification) or pyrite (pyritisation)

natural moulds can form when remains are washed away, leaving impression in the rock.

rules:

1. organism must be buried quickly to prevent decomposition etc

2. must be no contact with oxygen (promotes decomposition)

3. after burial must be no disruption to specimen

types of fossils:

• moulds: organism buried in sediment, slowly decomposes, leaving exact mould. if this is filled with another material eg. more sediment, it will produce exact copy, produces cast

• trace fossil: evidence of organism eg. tracks, burrows, freeding trails, coprolites

• soft flesh: rare, found mammoths in siberian ice

• actual hard parts: eg. bones and teeth of vertebrate animals/shells of invertebrate animals

• carbonisation: when buried rapidly with little/no oxygen. soft parts are converted to carbon-rich residue (dark imprint)

• petrification: preservation of skeletal material in its organic mineralised form

index fossils: used to define a period of geological time. must have distinctive appearance, short geological timeframe, widespread geographic distribution, hard parts to increase chance of fossilisation.often occur in ocean, as majority of fossil-bearing rocks found there. ediacaran: cloudinia (tiny shells) cambrian: trace fossils of treptichnus pedum (large, soft bodied animals with complex feeding patterns)

principle of uniformitarianism: geological changes are the result of observable, measurable natual processes that cause gradual change over long periods. “the present is the key to the past” and “the past is the key to the future”. broaden defintion to include cataclysmic events.

principle of superposition: within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence.

evolution of cambrian fauna

• evolution of jaws provided hard parts that fossilised well

• marked by layer where vertebrates appeared. however easy to locate at 541 +- 1 mya, because diversity/abundance of organisms

• zircon crystals in volcano magama chamber rocks dated using U/Pb dating

mass extinction events: