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Earth and Environmental Science- Dot Points
Unit 9.3 Environments Through Time
1.1a – Geological time is divided into eons on the basis of fossil evidence of different life forms

Phanerozoic- Occurred 544 million years ago to the present time. This eon was dominated by multicellular
organisms e.g. green plants, animals, fungi etc.
 Proterozoic- Occurred 2500 million years ago to 544 million years ago. This eon was dominated by
eukaryotic life, one celled organism. Early stromatolites were abundant.
 Archaean- Occurred 3800 million years ago to 2500 million years ago. This is where scientists have
documented the oldest rock, also this is the eon where life started off and became dominated by prokaryotic
life, one celled organisms, e.g. bacteria.
 Hadean- Occurred 4600 million years ago to 3800 million years ago. This eon is thought to of have no life
in it what so ever. This was when the earth was cooling and had just finished forming.
Note: Eons are divided into Eras then Periods then Epochs. All these different division have some sort of status in
showing key events in the formation of life on earth.
1.1b- Building a time line
Refer to exercise that was done in class of building a geological time line, showing the main or key events
throughout the earth e.g. ice ages, mass extinctions, when mammals, fish , reptiles and birds became abundant on
earth.
1.2a
Cyanobacteria- Are simple celled organisms; they were one of the first prokaryotic organisms to develop
successfully. They are simple photosynthetic organisms. They do not have a well-defined nucleus; they are often
referred to as Blue-Green algae. They can tolerate extreme conditions and aren’t affected by ultraviolet rays.
Fossil evidence of cyanobacteria in Australia
Australia contains some of the most important fossils on record in the world to teach us about the pasted. The
oldest known fossil on record dates back to 3460 million years old. These fossils are identified as stromatolites
from the Pilbara region in Western Australia. The majority of the stromatolites found there are from the
Proterozoic Eon. Some other spots these are found in are North Pole, Strelley Pool and Chinaman Creek areas of
Western Australia.
1.2b-Significance of BIF’s
BIF’s date the arrival of
cyanobacteria, because
they were the first
photosynthetic
organisms and this is
what helped to make the
iron oxide in the oceans
become insoluble and
form bands of orange
colours in rocks. But
there are periods when this orange colour isn’t present this means that the cyanobacteria might have been reduced
in numbers and the up welling of the iron oxide from the oceans wasn’t reaching the surface to turn insoluble.
These provide evidence of life in primitive oceans.
By Matt Royal
1.3a-Banded Iron Formations
 Exposed Proterozoic rocks that contained high levels of iron, once became weathered released iron salts.
 Because the iron had no free oxygen to react with in the atmosphere it entered the oceans as iron salts.
 Cyanobacteria when presence, they produced a waste product called oxygen. They lived on the upper layers
of the oceans.
 As the iron salts reacted with the oxygen being produced it sank to the sea floor forming layers of an orange
colour. This helped remove the oxygen from the cyanobacteria environment because the oxygen is toxic to
them and at the same time cleaned the oceans of iron salts. As this happened they would increase their
numbers till it got to great, then when oxygen levels rose to toxic levels for them it made a mass population
die-off. This is what is shown in BIF’s as a sediment layer rather then a rich orange colour. Then the cycle
would happen all over again.
1.3b-Habitat of modern stromatolites
Modern stromatolites live in the Hamelin Pool in Shark Bay, Western Australia. This Pool is hyper-saline, twice as
saline as usual sea water is, this is because there is a Bar across the bay and rapid evaporation in shallow waters.
Fish and other organism that would feed on the stromatolites normal can’t because they can’t tolerate the high
saline conditions. Modern stromatolites also live in hot spring environments such as Yellowstone national park in
the USA, they can also be found in such places as Antarctica and Africa.
The conditions most of these stromatolites are high stress for most living things thus no competitors for the
stromatolites.
Some of the characteristics of these harsh environments include: High saline, close to limestone (mineral rich water
i.e. calcium bicarbonate), water low in nutrients and very hot or very cold temperatures.
Possible reasons for their reduced abundances
GrazingImpacted upon from the main animals e.g. crustaceans and molluscs.
Increased nutrient levelsSuper phosphate is used in fertilizers on the agricultural land surrounding lakes. The fertilizer has encouraged the
growth of the aquatic alga.
This contributed to the decline in stromatolites.
Oxygenation of the oceansCyanobacteria work anaerobic, so when their waste product (oxygen) became abundant in the oceans it became a
harmful product for the cyanobacteria became they needed carbon dioxide to work. As the cyanobacteria died out
and oxygen became less abundant in the oceans it was shown in stripes called Banded Iron Formations.
These became a cycle where the oxygen would decrease and the cyanobacteria would become abundant and then
die out. But once all soluble iron was all used up in the oceans, it made the cyanobacteria to become restricted to
only harsh environments in now of days, e.g. Black smokers, hot springs high saline lakes etc.
1.4a The formation and range of fossil types
Fossil - Any remains, trace, or imprint of a plant or animal that has been preserved in the earth’s crust since some
past geologic or prehistoric time.
Types of fossils:
Original soft parts, unaltered: Very rare, needs special conditions to occur. E.g. insects in amber, animals in
permafrost and tar pits.
Original hard parts, unaltered: Most common with marine animals that had shells.
Original hard parts, altered: Internal structures may have been preserved.
Carbonisation: Nothing remains besides the carbon from the organism.
By Matt Royal
Coprolites: Organism waste products.
Premineralisation or Petrification: The impregnation of porous parts after burial in sediment, by mineral bearing
solutions
Impressions: these include casts moulds, tracks and trails.
How fossils form:
 Has to have a quick burial and most commonly have hard parts.
 Must stay undisturbed.
 Mainly occurs in water.
 Needs a continuous supply of sediment throughout time.
1.5a Stable isotope evidence for the first presence of life
Rocks older then 3 500 million years are subjected to experience intense metamorphism. This is one reason why
microfossils could have been obliterated.
Most livings things use carbon in some way there are two isotopes of carbon, Carbon 12 and Carbon 13.
During photosynthesis, cells preferentially build carbon-12 atoms into their tissues, leaving carbon-13 to
accumulate in the environment. So carbonates that come from living things should have a higher concentration of
carbon-12. The result is that the carbon in living cells and the carbon in the sedimentary carbonate have isotopic
compositions that can be matched.
This method has been used to find life that has been dated back 3 800 million years ago in Greenland, Australia
and South Africa.
But this has no relationship with the first life that was Arheaobacteria.
Part 2 The Environment of the Phanerozoic eon
2.1a Chemical relationship between the ozone and oxygen
Oxygen is made up of 2 oxygen atoms. It is generated by photosynthesis. When an oxygen molecule is struck by
ultra violet rays it is broken down into single oxygen atoms. This means single oxygen atoms that are floating
around will combine with 2 oxygen atoms to make Ozone (O3).
O2 + UV light → O + O then O + O2 = O3 (ozone)
Both UV-A radiation and UV-C radiation are totally absorbed by ozone but when UV-B radiation hits the Ozone it
breaks it back down into O2 + O. This becomes a cycle of breaking down and reforming.
2.2a Changes in Oxygen concentrations and the development of the ozone layer
 Oxygen was produced as a waste product from the first photosynthesising organisms, cyanobacteria. This
was used up by the sediment of soluble iron in the oceans. Once this stopped oxygen became free.
 Once oxygen became free in the atmosphere it started to form ozone with the formula from above.
 Once an ozone layer formed of the whole earth it blocked out harmful UV radiation that helped the
production of life.
 Thus making it suitable for land organism to be produced that would use aerobic respiration.
 But recently CFC’s have been breaking down the ozone layer and letting harmful UV radiation in.
2.3a The role of ozone in filtering out ultra violet light
 Ozone absorbed the UV radiation and thus remaking oxygen in the process.
 The ozone layer protects all living things that live on the surface of the earth from harmful UV radiation.
 Most organisms were anaerobic to start off with in the Precambrian times.
By Matt Royal


As oxygen accumulated in the atmosphere aerobic respiration could now take place.
Ozone also helped life to emerge on land at the beginning of the Phanerozoic eon.
2.1b Identify the major era subdivisions.
Era
Cainozoic (Cenozoic)
Time (Mya)
General life forms present
65
Mesozoic
248
Palaeozoic
545
1st primates. E.g. Mammals, birds
and Angiosperms dominated. Last
dinosaurs
1st Dinosaurs, Mammals and
flowering plants. Dinosaurs
dominated. Primitive marsupials
appeared.
Cambrian Explosion of life occurs,
many marine invertebrates. Also 1st
fish, 1st amphibians and 1st reptiles,
these all dominated.
Plants such as 1st corals, seaweed
and fungi, land plants these all were
dominate in this period.
Part 3 The Cambrian Event
3.1a Relative age of a fossil from a stratigraphic sequence
Sedimentary strata are laid down horizontally one on top of the other, to form a stratigraphic sequence. Meaning
that the oldest layer is at the bottom of the strata and the youngest at the top of the strata. So when an organism
becomes fossilised in one of these layers we can match up the layer to the age of the fossil. Therefore if a fossil is
at the top of a layer then it is the youngest, if it is at the bottom it is the oldest.
3.2a and 3.3a Uses and distinguishing between of absolute and relative dating
Relative dating: refers to the process of determining the age of a rock, fossil or event with respect to the standard
geological time scale. There is no reference to actual ages, say in years. Such dating relies on comparison with
other the rock layers, fossils or events such as intrusions, folding and faulting.
Absolute dating: is based on the decay of naturally occurring radiogenic isotopes in rocks to determine the age of
rocks in years. The age of a sample can be calculated from the measured proportions of parent to daughter isotopes.
E.g. Potassium – Argon dating, Half life =1.3 billion years
Uses:
Relative Dating: Determining the age of rocks or fossils by correlating stratigraphic sequences. This how the
geological time scale was developed.
Absolute dating: Determining the actual age of rocks or fossils in years by using radiometric or fission track dating
techniques. More volcanic rocks are used for this.
Half lives are used to determining the age of break down from when the parent rock first formed.
By Matt Royal
3.4a - The importance of hardened body parts explaining the Cambrian explosion.
There are 4 main points why hardened body parts explain the Cambrian explosion are:



Hard shells provided support for soft-bodied organisms and allowed a degree of protection from environmental
influences and predators.
Skeletons allowed the various animal groups to adopt new ways of life and to spread into previously
unoccupied areas on the seafloor.
The hard shells or armour developed by organisms of the early Cambrian period are easily fossilised, as
moulds, casts or altered by chemical means.
The fossil record increases in the number and type of fossils found due to the increase in organisms with hard
parts, so an apparent explosion of life seems to take place in the Cambrian period.
3.5a – possible advantages that hard shells and armouring would have given these life forms compared to
soft body organism
Firstly the shell or armouring of a organism gave it great chance of living on compared to the soft body organism
that were exposed to anything.
Predation Because of this new shell the organisms weren’t confined to a natural shelter. This means that they could
move around move in search of food.
 They had great manoeuvrability in aquatic environments by using the exoskeleton or limbs. This would
allow hard bodied organism to predate on the Ediacara metazoans.
Protection It was a natural shelter for the organism to hide in when a predator approached. This was much a greater
advantage because Ediacara metazoans had no way of protecting themselves.
 The shells also allowed protection from environmental factors, meaning that these hard bodied organisms
could with stand a drying out condition or dangerous conditions such as pounding sand and rock
particulars. This was much more better then the soft bodied organisms
Defence Having a hard shell deters predators. It also allows protection from any injuries from a predators attack.
Therefore having a hard shell or armouring was of great value to then next step in evolution and a good fossil
record.
3.1b – refer to other sheet
Part 4 Exploiting New Environments
4.1a Theory of Natural Selection.
Darwin and Wallace proposed the ‘Theory of evolution by Natural Selection.’ Wallace was studying African
mammals at the same time when Darwin was studying finches. (Refer to spot light pg50)
There theory is summarised below:
1. Each organism must face a constant “struggle to survive” and those best adapted to their environment will
survive best.
2. A species produces more offspring than can possibly survive.
3. There is variation within a species population and some individuals have types of variations that favour
their survival.
4. Organisms that survive will pass their favourable characteristics on to future generations.
5. The environment selects those individuals best suited for survival by the mechanism of natural selection.
By Matt Royal
4.2a Recall Evidence that present day organisms have developed from different organisms in the past
One the theory of that present day species had evolved from pasted organisms is that once the super continents
started to break up the species started to evolve into better equipped organisms to suit there environment and
climate conditions.
But a better way to show that present day species had evolved from past organism is the evolution of the horse.
The early ancestors of the modern horse walked on several spread-out toes. But when grasses became more
dominate the ancestor of the horse had to adapted to these new environments and therefore developed longer and
durable teeth, at the same time because there environment became more open and easier for predators to spot them
they had to be capable of out running them so the toes retracted and made one limb, this made the organism faster.
By retracting these limbs the organism became much large in size. Thus making it to what we see the species as
today. The horse shares a common ancestor with the tapirs and rhinoceros.
Another way of telling that present day organisms evolved from past species is the fossil record it shows the
gradual progression of simple life forms into more complex organisms.
4.3a Main evolutionary changes that organisms faced to survive on terrestrial environments
Animals
 Different gas exchange systems were developed. Lungs for breathing air which need to be supported and
kept moist internally.
 Development of a strong skeletal structure to support them with gravity, also to support organs.
 A whole different ear structure was developed for hearing.
 Internal fertilization some still lay eggs, mammals had internal development of young.
 Protective skin was needed to stop harmful sun rays.
 Management of a greater temperature, two different systems were developed Ectotherms (need the sun to
warm them up and get active for a certain time of period) and Endotherms (can produce there own body
temperature and adapted to other temperatures)
 Better ways of obtaining food, strong limbs, large teeth etc.
 Well developed circulatory systems.
Plants




Strong stems and support systems to support against gravity.
Waxy cuticles on leaves to stop evaporation of needed water from leaves.
Specialized leaves for gas exchanges and minimize water loss, development of stomates.
Extensive root systems to obtain water.
4.4a Outline major steps in expansion to the terrestrial environment by land plants, amphibians and
reptiles.
Plants
1.
2.
3.
4.
5.
6.
7.
8.
Small vascular plants near water
tough spores for reproduction
developed roots – better transport, then better shoots and leaves ( better transport and photosynthesis)
leaves with waxy leaves
leaves with stomata for gas exchange
woody tissue –larger, more support
first seeds in cones – survival with out water for reproduction
flowering plants – internal seeds and fruits – better dispersal and woody fruits resist drying
By Matt Royal
Amphibians
1. first amphibians similar to fish ancestors – they had 4 limbs, gills and were fully aquatic
2. moved into rivers and lakes onto banks – development of stronger legs and joints
3. stronger limbs and backbone
4. decreased toes
5. more defined neck
6. developed lung breathing
7. modification to the ear to allow better hearing
8. skin development
Reptiles
1. First reptile – late carboniferous
2. Scaly skin protects against desiccation
3. no gills, better developed lungs
4. waterproof, tough eggs – will not easily rupture on land or desiccate
5. small short, less heavy skull
6. chewing jaw
7. three dimensional movement of head on neck – better vision
8. later reptiles were hatched in more developed state – larger yolk
9. embryo floats in amniotic fluid
4.5a Identify Advantages enjoyed by first land dwellers
1. Abundant oxygen
2. More light for photosynthesis
3. More food production
4. Reduced competition for food and space
5. Easier to extract carbon dioxide from the air
6. protection from predators
4.1b Developed geological time scale –identify and date major evolutionary advances made by plants and
animals
Plants
Archaean Eon
 First eukaryotic organism – 1st single cell plants
Proterozoic Eon
 Stromatolites became very abundant
 First marine plants
3000mya
2400mya
1000mya
Phanerozoic Eon
Palaeozoic Era
 Cambrian event (mass explosion of life)
 First land plants (green plants and fungi)
 First vascular plants (Whisk ferns)
 Green plants become diverse on land
 Large primitive trees
By Matt Royal
Cambrian
Ordovician
Silurian
Devonian
Carboniferous
545mya
488mya
420mya
385mya
326mya



Conifer forest become abundant
1st cycads
Mass extinction
Carboniferous
Mid-Permian
End Permian
311mya
270mya
251mya
Mesozoic Era




Cycads and conifers dominant
Conifers dominant
1st angiosperms (flowering plants)
Major extinction event
Triassic
Jurassic
Cretaceous
End Cretaceous
250 MYA
161 MYA
100 MYA
70 MYA
Tertiary
65 MYA
Cainozoic Era

Angiosperms dominant
Animals
Proterozoic Era
 1st metazoans (Ediacara fauna)
640mya
Phanerozoic Eon
Palaeozoic Era
 1st shells (invertebrates with hard parts)
 1st Chordates and vertebrates (fish)
 1st corals, bryozoans
 Trilobites, brachiopods abundant
 1st land animals (arthropods)
 Tril, Brac, molluscs, fish abundant
 1st land vertebrates (amphibians)
 1st modern fish
 Coral reefs widespread
 1st reptiles
 Trilobites decline
 1st winged insects
 1st mammals-like reptiles
 1st beetles – insects dominant
 Major extinction event – most corals/tril die
Mesozoic Era
 1st mammals, dinosaurs
 1st large marine reptiles, turtles, frogs
 Molluscs, crustaceans common in ocean
 1st birds
 Dinosaurs dominant
 Dinosaurs dominant
 Major extinction event ( end of dinosaurs)
By Matt Royal
Cambrian
600mya
Ordovician
450mya
Silurian
440mya
Devonian
410mya
Carboniferous
350mya
Permian
290mya
End Permian
250mya
Triassic
240mya
Jurassic
205mya
Cretaceous
End Cretaceous
135mya
65mya
Cainozoic Era
 Mammals dominant (many types)
 1st humans (5mya)
 Modern humans
Tertiary
60mya
Quaternary
1.6mya
4.2b Summarize features and distribution of 1st land, amphibians, reptiles and compare to nearest modern
relatives
Earliest
Form
Features
Distribution
Modern
Form
Features
Land plants
e.g. liverworts
Small, simple,
spore bearing, non
vascular (no
xylem and
phloem)
Restricted to in
or near water
Land Plants Larger. Vascular with
e.g.
true roots, stem and
Angiosperms leaves.
Flowers with internal
fertilization.
Amphibian
Earliest is
Icthyostega
Crocodile like,
large head has
a tail fin,
covered in
scales
May still of used
gills, development
of primitive lungs,
strengthen of
backbone and
limbs to support
body.
Able to survive
out of water for
short periods.
Highly
dependent on
water for
breathing.
Therefore most
around lagoons
lakes oceans
and seas
Amphibians
e.g. frogs,
toads,
salamanders
Moist, smooth skin,
lungs in adults, gills in
offspring’s, eggs laid
in water
Mostly
dependent on
water but some
adapted to drier
conditions.
Reptiles
Evolved from
amphibians,
then arose into
mammal-like
reptiles e.g.
tortoises
Earliest know
reptile was
Westlothiana
Quite small,
Might of lived
looked similar to
close to water
living lizards,
small, short skull,
chewing jaw, three
dimensional
movement of neck
joint,
waterproofing of
eggs
Reptiles
Lizards,
crocodiles,
snakes,
turtles
Scaly, dry skin, well
developed jaws, eggs
protected by hard shell
World vast
adapted to arid
areas.
4.3b Compare the diversity and numbers from a fossil site
Fossil site- Riversleigh
Location: North-west Queensland
 Fossils from 25mya to present – This shows continuous change to present
By Matt Royal
Distribution
Many
environmentseven dry




It has 250 different sites that contain hundreds of species and thousands preserved
Shows the diversification of marsupials
Species found in this site include: early monotremes, marsupials, placental (bats), etc.
It has enhanced and broadens our understandings of the origins and evolution in animals of Australia.
Part 5 Past extinction and mass extinction events
5.1a Compare models of explosive and gradual adaptations and radiations of new genera
following mass extinction events


Gradual evolution, as proposed by Charles Darwin, is a process of slow and gradual change at a constant rate.
The number of species increases steadily.
Explosive evolution is characterised by periods of low and gradual change, followed by periods of rapid
change and diversification, with a rapid increase in the number of species.
Comparison:
 In both cases of gradual and explosive adaptations and radiations the organisms that are affected change to
suit their environmental changes. These can be expressed in a simple equation.
Low extinction rate = low adaptive radiation rate
High extinction rate = high adaptive radiation rate


An example of an explosive adaptation is the Cambrian explosion. Because organisms with hard parts
radiated so rapidly was because they had a significant advanced over the soft body organism for protection,
building of limbs, to use new area that was unoccupied.
An example of gradual adaptation is the tectonic movement of Australia from Pangaea to its present state. As
Australia drifted its environment became cooler, drier then warmer and drier, this made the rainforests to
recede to the coastline and vegetation evolved into woodlands, more grasslands and eventually desert. An
animal that evolved with these environmental changes is the kangaroo and relatives. From dwelling in
rainforests that made them small to becoming large with powerful legs to escape predators in open regions.
Both these theories explain some aspect of adaptation and radiation and that extinction is final.
5.2a Distinguish between mass extinction and smaller extinctions
Mass extinction: These include a world wide extinction of both terrestrial and aquatic organisms dieing out.
They have been shown that all the mass extinction has always wiped out more then 30% or more life on earth.
Examples include the end Permian extinction where 95% of all life died on the planet and the K-T event
(cretaceous, tertiary).
Smaller or regional extinctions: This happens when only some species die out in only one environment, weather
it is terrestrial or aquatic. Example of this is the extinction of the mega fauna.
Background extinction: this is the normal extinctions of a species in environmental changes. E.g. the dodo.
By Matt Royal
5.3a and 5.4a Analyse smaller extinction events involving several large species e.g. mega
fauna in Aust. (marsupials, birds and reptiles) and compare to mass extinction events
Mass extinctions
 5 major extinctions – more than 76% of all species were killed in these events in both aquatic and terrestrial.
 They affect species worldwide
 These are caused by massive catastrophic events e.g. comets (bolides), mass lava flows (Siberian traps),
major climate change (ice ages), change in sea levels
 Most species become extinct and survives usually become the dominate species. (explosive adaptive
radiation)
Small extinctions
 These aren’t affect whole ecosystems or change them.
 They are more localised then worldwide. (usually only happen in one region of the world)
 There are many different smaller extinctions in the geographical time scale
 Example:
The mega fauna of Australia that became extinct between 60 000 – 20 000 years ago. These mega beasts were
affected by the Aboriginals of Australia that used fire to altered and reduce the ecosystem on which the mega fauna
depended on, also hunting of the mega beasts for clothing and food, but at the end of the last glaciations these
organisms could not adapt to the shift from cold dry to warm dry conditions. Some examples of these Australia
mega fauna that were affected are:
 Genyornis, a large bird which was probably hunted to extinction
 Diprotodon, a marsupial weighting 1200kg
 Procoptodon, a 3m high kangaroo
 Thylacoleo, The so called Marsupial Lion was a tree dweller
 Zaglossus, a sheep sized echidna the largest monotreme ever
 Dromornis, a huge flightless bird; 3m high
 Megalania, Was a enormous carnivores goanna 7 m long
In more recent times since the European settlement of Australia it has lost 18 species of mammals and 100 plant
species.
5.5a Asses hypotheses proposed for the end Permian extinction with the popular bolide
impact theory for the end Cretaceous event
Permian – Triassic extinction
It occurred approx. 251 million years ago. It was the earth most serve extinction event, it killed off 96% of all
marine species and 70% of terrestrial vertebrate species. This event changed the environment that much it is
regarded as the boundary between Palaeozoic and Mesozoic Eras.
The major groups that were completely extinct by the end of this event include:
 Tabulate and rogues corals
 Almost all brachiopods
 Graptolites
 Trilobites
 Major fish groups
 Many land plants
 Many land vertebrates
Groups that survived sustained heavy losses, some survivors didn’t last for long after. The ones that barely
survived produced diverse and long lasting lineages. Recovery was very slow biodiversity took 6million years to
appear.
By Matt Royal
Theory 1
Bolide Impacts
June 2006 the discovery of the Wilkes Land crater in east Antarctica. It is 300miles wide more than a mile beneath
the ice sheet.
The Bed out Crater is found off the north-western of Australia. It has a 200km diameter. It also fits the time it was
thought to of hit. This is confirmed by the discovery of shocked quartz and brecciates mudstone. Caused worldwide catastrophic events.
Theory 2
Supernova
This occurred 32.6 light years away and could have depleted the ozone layer that would have caused major climate
change. No independent evidence is support to have happened at the right time.
Theory 3
Mass Volcanism
The Siberian traps was the largest volcanism recorded in history, it covered 200,00km². It happened over rich coal,
the heating of this released vast amounts of CO² and methane into the air causing serve global warming. There is
small timing difference between massive lava flows and the end Permian extinction, the direct and indirect impacts
on life would have been enormous. It was highly likely climate change occurred as a result.
It is likely that a very large impact would be associated with large volcanic emissions and massive climate change
except for the supernova theory, all the others fit into sink.
K-T event
It occurred 65.5 million years ago. It might not be as big as the end Permian but it is the most significant, it caused
major change in both marine and land ecosystems.
It exterminated the dinosaurs and affected sessile marine life.
The main groups that died out are:
Marine
 Ammonoids
 Rudists
 Mosassaurs and Plesiosaurs
 Planktonic organisms
Land
 Non – avian dinosaurs
 Pterosaurs
Ones that suffered heavy losses are:
 Birds
 Marsupials
 Freshwater mussels and snails
The organisms mostly unaffected are:
 Insects
 Amphibians
 Turtles
By Matt Royal
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



Plesiosaurs
Crocodilians
Modern birds
Monotremes
Placentals
Theory 1
Bolide
Sedimentary layers found all around the world at the C –T boundary contain a concentration of iridium hundreds of
times greater then normal. Iridium is highly rare.
It is suggested a bolide hit at the right time frame of the K - T event and is supported by composition of the K – T
boundary layer.
The problem was there was no crater that was documented; the Chicxulub crater was what fitted the description it
is a strong theory supported by several independent areas of research.
Theory 2
Mass Volcanism
The Deccan traps in India may be responsible for, or contributed to, the extinction. It was thought it happened in 1
million years but still it was too slow for this mass extinction.
Theory 3
Sea level regression
The sea level fells in the final stage of the Cretaceous. It would have greatly reduced the continental shelf area, it
would have caused climate change and reduced the albedo effect and increased global warming.
We only know of one sequence of rocks (the hell creek and lance formations around Montana) which has given a
detailed and continuous record of the final stages of the Cretaceous. This makes the bolide impact most in favour
of the mass extinction.
5.1b Compare two different concepts used to explain mass extinction events
What does ‘concepts’ mean here???
Interpretation 1
Mass extinctions may be of 3 types:
1. Catastrophic – very sudden
2. Stepwise – More extended, in pulses or episodes
3. Gradual – still over a fairly small time interval
Consider: A bolide impact may cause an immediate loss. Alternatively rapid climate fluctuations could trigger
episodic losses e.g. very warm conditions may follow very cold conditions. Similarly, losses of one group triggers
loss of another e.g. loss of forests leads to death of herbivores and then carnivores. Mass extinction may be a
mixture of the above: The end Cretaceous extinction may have begun with mass extinction due to an impact, then
mass lave flow followed causing further loss, the species may have become extinct as food sources disappeared.
Interpretation 2
Consider ‘concepts’ to be extinction mechanisms e.g. meteorite impacts, rapid climate change etc.
By Matt Royal
5.2b Identify the relationship between mass extinctions and the geological time scale
Mass extinctions caused large amounts of organism to become trapped and fossilized in a short period of time; this
is why more life is known around these mass extinction times because that is when most of the organisms are able
to become fossilized. Mass extinction usually occurs at the end of an Era because this is when a new environment
has been formed and doesn’t resemble the past environment, thus making it a new Era. With this it is clear that the
geological time scale has been planned to show the information of new life and environments that have evolved
from mass extinctions.
5.3b Two Hypotheses to explain the extinction of the mega fauna.
The kill theory: When humans arrived on the continent from other surrounding places the mega fauna that lived in
most of the southern countries didn’t have a chance because they had no idea that they were being hunted the only
mega fauna that is still alive today is the large organisms of Africa because the evolve with the humans with there
hunting skills and knew what was happening but because these hunters became so good at hunting there skill were
to developed for any other mega fauna to adapt to this change.
The Chilli theory: The theory suggests that large climate change from an ice age kill the mega fauna. Because of
this major climate change there habitat that they were adapted to was destroyed and because they were so fined
tuned to this environment they couldn’t adapt to the new environmental conditions. The problem with this theory is
it happened to slow for this rapid extinction.
By Matt Royal