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Past life, PAST CLIMATES - Coggle Diagram
Past life
Dinosaurs
First mammals:
- the earliest mammals first appeared around 210ma (late triassic) include the Morganucodon.
- have amniotic eggs like reptiles.
- have distinct jaw lines that set them apart from reptiles.
- believed to be small shrew animals that burrow
- found in patagoinia and argentina.
DINOSAURIA
- Stands upright (not sprawling like most reptiles)
- ball and socket hip joint
- straight ankle and knee joint
- ankle bones closely attached to the shin bone
dinosaurs evolved from the Archosaurs in the triassic around 230 Ma.they where smaller than the main dinosaurs. in the jurassic and early cretaceous, pangaea arrives and dinosaurs get huge. late cretaceous continents spread apart and dinosaurs are more spread out and new plants grew dinosaurs start to decline before the mass extinction.
EARLY TRIASSIC - ARCHOSAURS
- bi pedal predators 1-2m long
- Patagonia and Argentina only found fossils so far.
- during the triassic, the supercontinent Pangaea created a large, dry and hot interior. The Archosaurs thrived in this environment.
- Pangaea breaks during the Jurassic, however land bridges remained. climate was still warm, humid and large -> dinosaurs evolved.
- Type of reptiles
CRETACEOUS
- During this time, land bridges had gone and evolution moved along separate lines. Climate cooled down.
- size of dinosaur decreased. Possibly due to a change in diet as flowering plants increased due to climate change.
SAURISCHIAN
- Reptile hipped
- T-REX
- Pubis bone points forward.
- split into 2 groups:
SAURISCHIAN DINOSAURS:
- if it is carnivorous, it is saurischian.
- 'reptile or lizard hipped' dinosaurs, because they retained the ancestral hip anatomy also found in modern day lizards and reptiles.
- ALL saurischians became extinct at the end of the Cretaceous period apart from birds.
Three fingered hands that are asymmetrical.
- a little thumb allowed the hand to grasp things.
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SAUROPODA
- HUGE ( up to 30m long).
- four legged plant eaters ( herbivores) with long necks and tails.
long thin skulls, compared to the rest of the body.
- very long neck; allowed it to reach vegetation in forests that others cannot reach.
- no grinding teath; swallowed food whole aided by gastroliths and cheek teeth.
- extra bones underneath the spine; support and mobility of neck and tail.
- long tail possibly used like a whip (defence) also helps with balance.
THEROPODS
- bipedal, meat eaters, evolved into birds.
- ranged in size from T-REX >5 tonnes to turkey size
SCAVENGERS:
- Small arms - hard to grasp alive prey.
- huge back legs - slow at walking but could walk for long distances, better for scavengers.
- large olfactory lobes (very good sense of smell)
PREDATORS:
- Predators today will also scavenge for meat; just prefer fresh meat.
- not all predators need to use fore arms .
- few traces of t-rex so can't prove speed is slow.
ORNITHISCHIAN
- bird hipped
- STEGASAURUS
- Pubis bone points backward
- four legs
- small or absent teeth, replaced by a horny beak which became broader - duck billed dinosaurs.
- Armoured with bony plates- acts as a defence mechanism or for heat exchange.
- some developed horns - again likely for defence.
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EVOLUTION OF BIRDS
- birds evolved from therapod dinosaurs.
- Archaeopteryx had wings, feathers, hollow bones and a wish bone
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Evolution
EDIACARA
Precambrian life -> soft bodied organisms. -> poor preservation potential so fossilisation is rare (could have been metamorphosed, lost in subduction, destroyed) -> CHARNWOOD FOREST, charnia, a fossil of a plant
Australia and Canada:
- trace fossils of movement, organism looking for food.
- multicellular
- bilateral symmetry
- specialised body parts
- marine DEEP OCEAN so no light for photosynthesis = no plants
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CAMBRIAN EXPLOSION
there was life in the pre Cambrian but only soft bodied creatures. The Cambrian shows organisms with hard parts and have better preservation.
Ecological Explanations:
- More predators appeared so organisms developed hard parts for defence.
- in previously unexploited areas a poorly adapted organism may exist for a time (eg after glaciation)
Environmental Explanation:
- an increase of oxygen: more complex organisms, respiratory systems, circulation.
- BUT there was no sudden increase at the boundary. it is a slower change
- Glaciation: snowball earth -> when ice melts the few surviving species adaptively radiate into unoccupied habitats.
- BUT snowball earth occurred 90Myrs before Cambrian explosion. this times well with the Ediacara Fauna.
developmental: genome (genetic material) becomes complex enough that many different body plans can be produced
CAMBRIAN LIFE: the Burgess Shale:
Trilobites,
Hallucigenia (legs and spikes)
Opabinia (lots of eyes)
Anomalacaris - Predator.
EVOLUTION
Phyletic gradualism = Darwin-wallace theory, survival of the fittest. A GRADUAL CHANGE BUT NOT MUCH SUPPORT IN FOSSIL RECORD.
- Also shown by Graptolites, Humans and Trilobites
Punctuated equilibrium = long periods of no change and then a sudden change. seen in the fossil record. Fits most of what we see in the fossil record, but does not make it correct as the fossil record is incomplete and biased to marine animals.
SEPKOSKI'S CURVE: shows marine diversity and an overall increase in diversity through the Phanerozoic
- Cambrian fauna: Trilobites (burgess shales)
- Palaeozoic fauna: cephalopods , brachiopods, corals (reefs) and crinoids. More predator pressures
- Modern fauna: bivalves, fish and vertebrates (burrowing is common)...
How did life evolve?:
- Bombardment
During its early history, earth was bombarded by meteorites so life couldn't thrive.
- In the sea:first living things
life evolved slowly after the bombardment, the first living things were bacteria.
- Oxygen
early photosynthetic bacteria produced oxygen and released it as a waste product.
this added oxygen to the atmosphere for the first time.
- small multicellular life, 1400 ma
- algae evolved sexual reproduction, 1200 ma
- ediacara fauna 630-542 Ma
- Cambrian explosion, 541 ma.
Organism types:
- prokaryotes: cells with DNA strands floating in a capsule. these include various types of bacteria. These were the first living things on earth.
- Eukaryotes: complex cells that have compartments with special jobs and DNA in a nucleus.They need Oxygen to survive. e.g animals, plants, fungi. these appeared later.
Evolution of plants:
- the emergence of plants onto land occurred about 500ma (Cambrian) as the most primitive of the living plants today with shallow root systems.
- they probably formed a spreading mat over the surfaces of wet soils and created a habitat which animals could begin to colonize.
plants as food
- the first animals to come onto land were either carnivores or detritivores (living off dead organic matter).
- however 420ma fossil coprolites excreted by millipedes and related animals contain the remains of plants, showing that the first herbivores where insects.
First forests
- 380 ma, some plants had trunks that formed leafy canopies.
- at the same time plants were changing the way they reproduced. the earliest plants had reproduced with spores, as ferns do today. Now they have developed seeds.
- once the seeds had evolved, the plants had the capacity to colonise dry land away from the coast.
First tropical rainforests
- 300ma life on land was really thriving.
- across Europe and North America the first tropical rainforests developed, which when they died created thick layers of coal.
- fossils show that these rainforests were inhabited by a rich diversity of animals including giant sized dragonflies and millipedes.
Evolution of Amphibians:
- the first land dwelling creature with four legs known as Tetrapods. They evolved from lobe finned fish in the late Devonian to early carboniferous
understanding not fully correct. most are terrestrial animals -> fossil record is bias to marine fossils.
lobe finned fish: members of a largely extinct group with fleshy lobed fins with an arrangement of central bones inside, similar to the structure of bones in a hand. This allowed for mobility on land. - The problem was there was no STRENGTHENING GIRDLE connecting the bones at the extremities to the rest of the skeleton, this gave areas of weakness.
- the fins later evolved to hands.
lobe finned fish also have the ability to breathe in and out of water due to their advanced lungs that were modified swim bladders. swim bladders are sack like structures that fish use for buoyancy by filling it with gas or fluid.
similarities of lobe-finned fish and early amphibians:
- four fins
- limbs in the same position, fin bones are also in a similar configuration as a hand.
- both lacked claws and nails
- skull morphology; jaw bone and teeth are alike
- early amphibians still had tails
- streamlined shape
- early amphibians had scales.
Adaptations to life on land ( differences ) :
- Development of girdle connecting limb bones to the skeleton; better movement on land.
- more robust skeletons including strengthened rib bones.
- eyelids formed to help keep eyes moist as they weren't always in the water.
- three chambered heart so more cells could be provided with oxygen.
- a tongue formed; catching prey
- Ears grew; hearing for prey.
- could have eggs on land
differences of lobe finned fish and early amphibians:
- streangthening girdle link.
- stronger ribs to support weight and protect organs.
- eye lids to keep the eyes moist on land.
From amphibians, evolved reptiles
-> amniotic egg - allows terrestrial mode of life.
- evolved into dinosaurs. the Archosaurs in the triassic.
- Konzentrat-lagerstatten= many organisms in one bed.
- Konservat-lagerstatten= exceptional preservation- very fine detail and perhaps some soft tissue.
mass extinctions
Extinction of a species occurs when deathrate > birth rate for a sufficiently long period of time.
They are common and occur due to factors like competition with another species or a local change in environment.
This 'normal' rate of extinction is termed background extinction.
When the extinction rate increases significantly above this background extinction in a geologically small period of time, this is called a mass extinction. >30% become extinct.
PERMO-TRIASSIC/ END PERMIAN EXTINCTION:
- around 252 ma
- gradual decline in species over 15 million years.
- around 95% of marine life became extinct. Including trilobites, corals and brachiopods.
- land plant, vertebrates and insects extinctions.
- evidence found worldwide.
SUMMARY
- Siberian Traps. Major volcanic activity. (ash blackout that cools down the earth- blocks sunlight. Magma heats up the methane hydrates)
- Super continent formation/Glaciation (oceans and coasts disappear)
- Methane Hydrates. (global warming)
Sea levels: some researchers presenting evidence for a sea level rise at the boundary but others say sea level fall.
- With a transgression oxygen poor deep water could have moved onto continental shelf- suffocating many species.
END CRETACEOUS MASS EXTINCTION 66MA:
- A meteroite that landed in Chixulub, Mexico
- Deccan Traps, India. Major volcanic activity = Sunlight blockage. Magma heating up methane hydrates = global warming. long term temperature rise.
- a fall in sea level meant that shallow marine animals where declining
- fern spike and fossil record shows a decline in species from background extinctions.
THE K-Pg BOUNDARY
- The presence of a thin 2cm iridium-rich clay is found worldwide in sedimentary rocks. They all date back to the same time 66 ma.
- iridium is rare on earth as it is a transition element and is common in meteroites.
TEKTITES
- natural glass rocks up to a few cm in size.
- most scientists agree they are formed by the impact of large meteorites on Earth's surface.
- Tektites are black or olive-green in colour and their shape varies from rounded to quite irregular
- they where found inside the crater
ASTEROID IMPACT LOCATION
- Location of possible impact site discovered in Chixulub, Mexico.
- a circular depressio with about 180km diameter
- In addition, sulphur released into the atmosphere reacted with water droplets to create sulphuric acid -> acid rain.
-this would have killed many plants and marine organisms would have their calcite shells dissolved due to the acidic increase in the sea water .
SHOCKED QUARTZ
- Found worldwide as a thin layer at the boundary between the Cretaceous and the Palaeocene rocks.
- First discovered at nuclear testing sites and later in meteorite craters.
- shocked quartz has a microscopic structure different from normal quartz.
- under intense pressure, but relatively low temperature, the crystalline structure of quartz is deformed along planes inside the crystal.
- These planes, which show up as lines under a microscope are called PLANAR DEFORMATION FEATURES or SHOCK LAMELLAE
SOOT FROM WILDFIRES
- the k-pg layer has high concentrations of carbon in some locations, suggesting that the asteroid impact may have generated wildfires.
- large areas of vegetation would have been destroyed in a short time.
- soot would be blown by the wind so fires themselves where not global.
TSUNAMI DEPOSITS
- It is thought that the asteroid impact occurred in the sea and initially produced a crater 100km wide and 30m deep.
- this would have displaced vast volumes of seawater nd generated a series of very large tsunamis possibly over 100m in height.
- the tsunamis would have travelled inland over to Texas where there is large-scale sandstone deposits thought to be of tsunami origin.
the meteorite hit an area with a significant amount of gypsum that flew into the atmosphere and reacted with h2o to create sulphur dioxide and thus acid rain and make the oceans acidic and dissolve shells
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PAST CLIMATES
The Wilson cycle
- (stage A) continental rifting:
- rising mantle
- tension
- thinning of continental crust
- (Stage B) rifting of continental lithosphere
- divergent plate margin formed
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- Drifting/ ocean formation
- opening of an ocean basin.
- central ridge
- passive margins on each side.
- ocean getting bigger/wider until subduction begins at margins.
- the lithosphere in the middle of the ocean gets older and more cold, dense and has negative buoyancy so it starts to subduct.
- Closure:
- subduction
- convergent Plate Margin
- Closing ocean
- collision and closure
- trenches = subduction
- ocean getting smaller
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if there is lots of mountain building, then there is an increase in chemical weathering.
- The long term carbon cycle
- co3 ions carried in solution to the ocean
- used in shells etc
- less co2 in the atmosphere
- global temperature decreases.
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Climate + weather
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MODERN CLIMATE SYSTEMS
Atmospheric circulation: is the large- scale movement of air, and the means (together with the ocean circulation) by which heat is distributed on the surface of the earth.
- The warm air found around the equator can mix with cold air from the poles.
- This air movement forms convection cells and jet streams ( fast moving air currents between areas of great temperature differences)
- the large-scale structure pf the atmospheric circulation varies from year to year, but the basic structure remains fairly constant.
Factors that influence the temperature of the earth's surface:
- heat output from the sun
- distance between the Earth and the sun
- the tilt of the Earth
- speed of rotation of the earth
- composition of the earth's atmosphere
- the albedo of the earth which varies with:
- cloud cover
- the area of the ice sheets
- the amount of volcanic activity; clouds or ash
Atmospheric circulation 2:
- the earth is spinning and we have more sunlight and heat on the equator and less at the poles.
- the wind belts and the jet streams circling the planet are steered by three cells:
- the Hadley cell.
- the Ferrel cell
- the polar cell
- This is also due to water having a higher specific heat capascity than land and therefore water absorbs and releases heat less readily than land.
- even at micro sales, this effect is noticeable: it is what causes the sea breeze, air cooled by the water, ashore in the day, and carries the land breeze, air cooled by contact with the griund, out to sea during the night.
- for example, the pacific cell is the site of the El Niño or Southern oscillation
The Hadley cell: is best understood. it forms a closed circulation loop, which begins at the equator with warm, moist air lifted aloft in equatorial low pressure areas to the tropopause and carried towards the pole.
- At about 30°N/S lattitude, the air depends in a cooler high pressure area. some of the defending air travels equatorially along to surface, closing the loop of the Hadley cell and creating the trade winds.
Ocean circulation:
- sinking cool water, rising warm water and wind help to form global ocean current systems.
- it is the second way heat is distributed over the globe. this is done by surface currents and also deep global currents.
surface currents
- the ultimate reason for the world's surface ocean currents is the sun. The heating the earth by the sun has produced semi-permanent pressure centres near the surface as we saw in the last slide. When wind blows over the ocean around these pressure centres, surface waves are generated by transferring some of the wind's energy, in the form of momentum, from the air to the water. This constant push on the surface of the ocean is the force that forms the surface currents.
Driven by the sun. the sun heats the planet and creates high and low pressure. The wind blows over the ocean around pressure centres and drags the water with it.
Deep currents
- there is also global circulation which extends to the depths of the sea called the Great ocean conveyor. Also called the thermohaline circulation, as it is driven by differences in the density of the sea water which is controlled by differences in the density of the sea water which is controlled by temperature and salinity.
Driven by the density differences (which in turn link to temperature). Also called thermohaline circulation.