Download Environments Through Time

Environments Through Time
1 Evidence from
early Earth
indicates the first
life forms survived
in changing
habitats during the
Archean and
Proterozoic eons
 identify that geological time is
divided into eons on the basis of
fossil evidence of different life
forms
 define cyanobacteria as simple
photosynthetic organisms and
examine the fossil evidence of
cyanobacteria in Australia
 outline the processes and
environmental conditions involved
in the deposition of a Banded Iron
Formation (BIF)
 examine and explain processes
involved in fossil formation and
the range of fossil types
 outline stable isotope evidence for
the first presence of life in 3.8 x
109 year-old rocks
 gather and process
information from secondary
sources to draw up a timeline
to compare the relative
lengths of the Hadean,
Archaean, Proterozoic and
Phanerozoic eons
 gather and analyse
information from secondary
sources to explain the
significance of the Banded
Iron Formations as evidence
of life in primitive oceans
 gather, analyse and present
information from secondary
sources on the habitat of
modern stromatolites and use
available evidence to propose
possible reasons for their
reduced abundance and
distribution in comparison
with ancient stromatolites
Geological time and eons:
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The geological time scale is divided into 4 eons: Hadean, Archaean, Proterozoic and Phanerozoic. They are divided
on the basis of fossil evidence of different life forms.
Hadean: (4.5-4 b.y.a) no rocks have survived from this period. Zircon (pieces of original rock have evidence of life)
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Archaean: (4-2.5 b.y.a) granitoids; greenstones; basalts and pillow rocks (only formed in the oceans therefore
oceans must have existed). All the rocks were highly metamorphosed. Cores of continents formed during this eon.
Very ancient life forms (trace fossils only)
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Proterozoic: (2.5 b.y.a-545 ma) plate tectonic super cycle established. Sedimentary rocks deposited on crust
(sandstone, conglomerate, mudstone, limestone). Fossil bacteria and algae
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Phanerozoic: (545 ma –present) Complex fossils with hard parts appear. Lots of material is added to continents at
subduction zones
Cyanobacteria, stromatolites and banded iron formations
-
Cyanobacteria were the first organism to use photosynthesis as a means to respiration
Cyanobacteria are simple photosynthetic organisms
Sunlight/chlorophil
Carbon dioxide + water --------------------------- Glucose + oxygen
Cyanobacteria and Fossils:
-
The remains of cyanobacteria can found as stromatolites in Western Australia
The North Pole district in Western Australia is home to many stromatolite fossils
Stromatelites found in Marble Bar W.A in the Pilbura Region are the oldest fossil evidence for the presence of
cyanobacteria 3.5 BYA
a stromatelite is a rocky layered deposit formed by communities of Cyanobacteria
Modern Stromatolites require:
-
shelter from predators
warm water
hyper saline shallow water
low amounts of tidal flushing
form domes, mats, columns or cones
Conditions which stromatolites needed:
-
Required protection from UV light, a few metres under water was suitable
warm; shallow; hypersaline water, shelter from predators and low amounts of tidal flushing.
-
Stromatolites have declined over millions of years this is due to an increase in oxygen concentration , this would
reduce the population of cyanobacteria
Banded iron formations and chemical precipitation:
-
Banded iron formations are sedimentary deposits of banded iron oxide which are composed in alternating layers
Formed through chemically precipitated iron oxide
Most Banded iron formations were deposited 2 – 2.5 bya
Chemical Precipitation:
-
Photosynthetic cyanobacteria produced oxygen and oxygenated the upper layers of the ocean. This oxygen caused
chemical precipitation
The ocean was rich in dissolved in iron, oxygen reacted with this iron to create iron oxide, which precipitated to the
bottom of the sea floor and formed alternate layers
The formation of banded iron moderated and controlled the amount to oxygen in the atmosphere, when all the
dissolved iron was precipitated there was an explosion of oxygen in the atmosphere
Discuss the significance of BIF’s as evidence of life in primitive oceans:
- BIFs provide evidence of primitive life in the oceans by the presence of oxygen that must have been caused by
photosynthesis by life forms.
Fossil formation and fossil types
-
Fossils are the preserved remains or impressions of prehistoric life forms or evidence for their existence
-
MOULD - the shape/imprint of the organism
CAST - the imprint filled in with new minerals
Conditions required for fossil formation: (BSCA)
1. Burial (rapid)
2. Sediment (continual supply of sediment to avoid erosion)
3. Compaction (of sediment)
4. Anoxic conditions
-
Fossil formation is unlikely for a number of reasons
o Many deceased organisms are eaten by scavengers or broken down by microbes
o The conditions for burial are not met ie rapid burial, continual supply of sediment, compaction and anoxic
conditions
Fossil forms:
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Unaltered soft parts – When bacteria and mould are prevented from acting of soft tissue
Unaltered hard parts – Soft tissue is decomposed, however, hard parts remain eg bones
Altered hard parts – When fossils undergo physical and chemical changes. Eg hard parts replaced by with silica,
pyrite or iron oxide.
Trace fossils – Fossils leave a mould which is filled in by minerals creating a cast. These can be in the forms of
imprints of organisms and burrow
Fossil types:
- Examples
o Unaltered soft parts
 Mammoths in Siberia
 Animals trapped in tar pits
o Unaltered hard parts
 Shells of mollusks
 Hard parts of insects in tree resin
o Altered hard parts
 Petrified wood
 Carbonisation where a fossil turns to black carbon
o Trace fossils
 very common
 impressions and moulds
 Casts of original organisms
 Footprints of organisms eg dinosaurs
Evidence for first life:
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The earliest evidence of life is found in metamorphosed sedimentary rock 3.8 b.y.o found in ISUA, WEST
GREENLAND. The graphite minerals enriched in Carbon 12 in these rocks provides a “signature” of life. There is a
high Carbon 12: Carbon 13 ratio
2 The environment
of the
Phanerozoic eon
 outline the chemical relationship
between ozone and oxygen
 explain the relationship between
changes in oxygen concentrations
and the development of the ozone
layer
analyse information from secondary sources to
identify the major era subdivisions used to
describe the Phanerozoic and describe the
general differences in life forms in each era
 describe the role of ozone in
filtering ultraviolet radiation and
the importance of this for life that
developed during the Phanerozoic
eon
Chemical Relationship between ozone and oxygen:
-
Ozone is formed in the stratosphere (upper atmosphere
Ozone is formed when UV rays separate 02 (oxygen) into separate 0 molecules
As 0 atoms are extremely unstable they are forced to react with a nearly atoms usually other 0 atoms or 02 atoms
If they react with 0 atoms then 02 will be formed, however, if reacted with 02then 03 (Ozone) will form
0 + 02  03
Changing oxygen concentrations and development of ozone layer
The presence of oxygen in the atmosphere:
– increased ozone production and therefore reduced UV radiation that reached earth
– This allowed for organisms to evolve into more complex life reducing the UV damage emitted by the sun
– increased oxygen lead to global cooling (previously the Archaean was very warm as it had high CO2 levels)
Role of Ozone and importance:
-
the introduction of ozone layer meant that life could evolve beyond the deep areas of the ocean
ozone is able to filter and prevent most of the dangerous UV radiation from reaching earth therefore moderating
and controlling global temperature
This is important as UV radiation is very damaging. Terrestrial organisms need ozone in order to prevent cellular
death by disrupting DNA, mutations (cancer), cataracts (in eyes), sunburn, and death of some organisms
Identify the major era subdivisions used to describe the general differences in life forms in each era: The Phanerozoic Eon
Eon
Era
Life Forms
Cenozoic (144 ma-present)
-mega fauna extinction
Phanerozoic
-mammals, birds and flowering plants dominate
-homo sapiens
Mesozoic 248-144 ma
-flowering plants
-land organisms dominate
-reptiles and dinosaurs
Paleozoic 540-248 ma
-first jawed fish
- vertebrates
-amphibians
-land plants
3 The Cambrian
event
 interpret the relative age of a fossil
from a stratigraphic sequence
 compare uses of relative and
absolute dating methods in
determining sequences in the
evolution of life forms
 distinguish between relative and
absolute dating
 discuss the possible importance of
the development of hardened
body parts in explaining the
apparent explosion of life in the
Cambrian period
 process information to
examine at least one example
of a stratigraphic sequence
and describe any fossils found
in this sequence
 use available evidence,
including computer
simulations, models and
photographs to examine the
changes in life forms that
occurred during what is
commonly referred to as the
‘Cambrian event’
 deduce possible advantages that
hard shells and armouring would
have given these life-forms in
comparison with the soft-bodied
Ediacara metazoans of the late
Proterozoic, in terms of predation,
protection and defence
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The Cambrian Event
The Cambrian explosion/event was the almost immediate radiation of shelled organisms during the early Cambrian
The Cambrian Period marks the boundary between the Proterozoic and Phanerozoic eons and the almost
instantaneous appearance of a variety of shelly animal fossils which are ancestors of present day life e.g. the Pikara
Graciens
At this boundary there is a distinct transition between soft-bodied organisms to hard shelled creatures
50 ma after the Cambrian boundary there is an increase in complexity of fossils
possible events that caused the Cambrian explosion
o Increased oxygen supply allowed larger organisms to survive
o Predation allowed organisms to obtain more nutritious food supply (theory not proven)
o Genetic mutations increased the rate of evolution (theory not proven)
Distinguish between relative and absolute dating
- Relative dating is a type of dating, whereby the rock is compared to other rock layers. Ie rock layer 2 is older then
layer 3 but younger then layer 1
Law of superposition, states that the rock layer on top of the previous rock layer is older. (see below)
-
Absolute dating determines the age of specimens
Absolute dating is achieved through radiometric dating
Components of atoms
o Neutrons (n)
o Protons (p)
o Electrons (e)
Compare uses of relative and absolute dating methods in determining sequences in the evolution of life forms
Relative dating
refers to determining rock/fossil age in reference to other rock layers and the geological time scale. It does not
classify a rock strata in terms of years.
Absolute dating
- determining the exact age of a rock/fossil in years
- The rock must be igneous
- Radioisotope dating is based on the decay of radio isotopes found in the rocks to determine the fossil/rocks age in
terms of years. Half lives are used to determine the age of breakdown from when the parent rock first formed.
Half Life, the half life of an isotope is how long it takes for half of the parent isotope to decay into the daughter
isotope.
If the rate of decay of isotopes is known then it is possible to compare the amount of parents isotopes present with
the amount of daughter isotopes present to determine age
Example:
o Potassium – 40 -> Argon – 40
o Carbon – 14 -> nitrogen - 14
Discuss the possible importance of the development of hardened body parts in explaining the apparent explosion of life in
the Cambrian Period
There are 2 main points why hardened body parts explain the Cambrian explosion:
1. Hard parts provided support for muscle joints and internal organs in organisms and offered protection from
predators and harmful UV rays allowing these organisms to better survive and move onto life where food availability
was higher
2. Hard parts are easily fossilized unlike soft parts leading to an increase in fossils with hard parts found so a sudden
explosion of life seems to occur during the Cambrian Period.
Deduce possible advantages that hard shells and armoring would have given these life-forms in comparison with the soft
bodied Ediacara metazoans of the late Proterozoic, in terms of predation, protection and defense
–
Hard parts provided animals with
o protection from predators
o a skeleton to provide a framework to support feeding organs of filter feeders and suspension feeders
o skeletons allow organisms to grow larger and therefore more protection from predators
o skeletons also provide firm points for muscle attachment to improve mobility
o protection from UV
o stops organisms in intertidal zones from drying out during low tides
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The Cambrian animals had an advantage over the Ediacara Metazoans as they had hard parts and were more mobile
which allowed them to escape from their predators and move to areas where more food was available.
4 Exploiting new
environments
 outline the theory of evolution by
natural selection
 outline evidence that present-day
organisms have developed from
different organisms in the distant
past
 gather and analyse
information from a geological
time scale and secondary
sources to identify and date
the major evolutionary
advances made by plants and
animals
 summarise the main evolutionary
changes resulting from the
selection of living things exhibiting
features that allowed them to
survive in terrestrial environments
 gather information from
secondary sources to
summarise the features and
distribution of some of the
first land plants, amphibians
and reptiles
 outline the major steps in the
expansion to the terrestrial
environments by land plants,
amphibians and reptiles
 gather information from
secondary sources to
compare the diversity and
numbers of organisms from a
fossil site
 identify the advantages the
terrestrial environment offered
the first land plants and animals
Outline the theory of evolution by natural selection
-
Organisms that are best suited to the environmental conditions will survive. These organisms will multiply producing
offspring with their favorable characteristics/genes. They will dominate the population and the others will die out.
Outline evidence that present-day organisms have developed from different organisms in the distant past
- the fossil record shows the gradual progression of simple life forms into more complex organisms
- Comparative embryology
o The comparison of embryos in organisms
- Anatomy
o The structure of an organism such as the pentadactyl limb found in a variety of organism including humans,
horses, lizards, cats and birds
- Biogeography
o Where similar things live and their habitats
o For example the golapocus islands
o The crimson rosella and the eastern rosella
- Physiology
o The functioning of an organism
o Eg Hemoglobin
- Biochemistry
o The analysis of DNA and Proteins.
o Many organisms have similar cell structure and function.
o The more similar the DNA and proteins in organisms the more closely related they are
o DNA analysis has become the most sophisticated and used means to determine evolution and similaritie
TGA fly
TGA Frog
TAG Mouse
GGG cockatoo
DNA sequencing
TGA common ancestral sequence
Summaries the main evolutionary changes resulting from the selection of living things exhibiting features that allowed
them to survive in terrestrial environments
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Water
o Plants developed roots to ground themselves into the soil and absorb water
o Plants also developed an epidermis which reduced the amount of water lost
o Animals developed more complex nervous systems which would allow for animals to sense and locate water
o Animals developed skin which reduced the amount of water lost
Oxygen
o Plants developed stomates which stopped water imbalances through respiration
o Plants created oxygen the process of photosynthesis
o Animals developed lungs which allowed for aerobic respiration
Reproduction
o Evolved seeds which were able to spread via the wind, water and by other animals thus transporting
offspring over large areas
o Animals developed internal fertilization
Energy
o Plants developed a supportive structure which allowed them to be closer to the sun and as such
photosynthesis would occur easier
o Animals waited until plants moved to the terrestrial environment as plants were an energy source for
animals
Identify the advantages the terrestrial environment offered the first land plants and animals
Advantages
Disadvantages
- more abundant O2
- direct exposure to air=drying out therefore animals
developed scaly skin
-
more light for photosynthesis
-
new mode of fertilization needed which lead to the
development of internal fertilization and hardshelled eggs for protection
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more available habitats
-
lung development needed (evolution)
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less competition for food
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gravity force is greater on land and therefore
skeletons (fauna) and lignin (plants) were developed
to hold against gravity
Outline the major steps in the expansion to the terrestrial environments by land plants, amphibians and reptiles
- All life was marine based until the Ordovician. Early plants colonized near shore environments which encouraged
animals to move closer to the food supply
1) Plants
2) Insects
3) Animals
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Precambrian
o Cyanobacteria
o Metazoans
Cambrian
o Anthropods
o Brachiopods
Ordovician
o Fish
Silurian
o First vascular land plants – liverworts
o First land animals
Devonian
o Amphibians
o Land plants
Carboniferous
o Reptiles
Permian
o Mammal like reptiles
o Ammonites
Triassic
o First mammals
o Dinosaurs
Jurassic
o Flowering plants
Tertiary
o Hominoids
Lobe
Jawless bony – plated fish
Fish with Jaws
Bony Fish
Cartilaginous fish
Early amphibians
Modern amphibians
Primitive reptiles
Modern birds
Modern reptiles
Mammals
5 Past extinction
and mass
extinction events
 compare models of explosive and
gradual adaptations and radiations
of new genera and species
following mass extinction events
 distinguish between mass
extinctions and smaller extinctions
 explain the recent extinction of the
marsupial, bird and reptile
megafauna in Australia, as an
example of smaller extinction
events involving several large
species.
 compare these smaller extinction
events with widespread
‘catastrophic’ events in which
entire ecosystems collapse with
the extinction of many entire
classes and orders
 gather, analyse and present
information from secondary
sources to compare two
different concepts used to
explain mass extinction
events
 gather information from
secondary sources and use
available evidence to identify
the relationship between
mass extinctions and the
divisions of the geological
time scale
 analyse information from
secondary sources on at least
two different hypotheses
used to explain the extinction
of the megafauna
 assess a variety of hypotheses
proposed for the mass extinctions
at the end of the Permian and at
the end of the Cretaceous
Compare models of explosive and gradual adaptations and radiation of new genera and species following mass extinction
events
- Radiation:
o occurs after extinctions when the remaining groups of organisms undergo rapid evolutionary expansion to
replace the lost organisms.
o The new genera or species that radiates have similar features to their ancestors but are specifically adapted
to their environment.
o After this, rates of evolution slow dramatically due to increased competition for food/shelter and predators
therefore only new genera or species evolve opposed to phyla and classes.
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The geological timescale indicates that there is a constant cycle of extinction and radiation.
The fossil record indicates that evolution has occurred gradually and quickly (in geological terms)
Gradual: When evolution occurs over a long period of time through continuous changes in
Explosive: punctuated equilibrium theory proposed by Eldridge and Gould suggests that evolution occurs by rapid
bursts of change within an organism followed by long periods of stability
Past extinction and mass extinction events
Extinction: when species die out. They occur due to meteorites, volcanoes, regression/transgression.
Radiation: when the survivors of the extinction radiate and flourish replacing the lost organisms
Ecological Niche: the place of a plant or an animal within its ecosystem or community
Distinguish between mass extinctions and smaller extinctions
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Mass extinctions
o Affect a variety of species over a large area potentially globally or in most areas of the world
o Typically relatively brief and followed by explosive radiation bringing about new species and a new genetic
variety
o Such as the K/T Cretaceous and Permian extinction
Smaller extinctions
o Affect only a relatively small amount of species in a relatively small area
o Such as extinction of Australian megafauna
Explain the recent extinction of the marsupial, bird and reptile mega fauna in Australia, as an example of smaller
extinction events involving several large species.
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The Australian megafauna extinction is considered a small extinction as it occurred in one particular geographical
area and a number of species managed to survive
There are two theories to explain the extinction, it could have been a combination of the two
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Climate change
o occurred 18 000-22 000 years ago
o Australia’s climate became more arid as it drifted northward- changed from cold and dry to warm and dry
o ecosystems changed from forest to grassland and surface water became scarce
o many organisms lost their habitats and these pressures were too extreme to adapt quickly enough
o Smaller species managed to survive as they are in need of less food and are able to reproduce more
offspring
-
Human intervention
o Aboriginal human intervention at fault
o mega fauna’s large size made them slow making them vulnerable to human predation
o human arrival coincides with the beginning of the extinction
o Some evidence of attacks on megafauna found in fossil remains of bones
o humans also induced vegetation change such as back burning
o unable to adapt to the introduction of human predation
Compare these smaller extinction events with widespread ‘catastrophic’ events in which entire ecosystems collapse with
the extinction of many entire classes and orders
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The Permian extinction occurred at the end of the Permian
The extinction caused the death of almost 95% of species on Earth
The extinction was on a global scale affecting all species
The extinction was either caused by a catastrophic event ie a bolite collision, a gradual event such as sea level
changes or a combination of both
Assess a variety of hypotheses proposed for the mass extinctions at the end of the Permian and at the end of the
Cretaceous
Catastropic: Cretaceous K/T
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Suggests a bolide (meteorite ) hit earth killing all organisms
o The bolite may have triggered large tsunamis
o Caused bushfires on a large scale
o Caused death to organisms in immediate vicinity
o The resulting ash cloud may have caused a global cooling affect
Evidence for bolide impact:
o Impact crator (chixulub crator)
 Located in the golf of Mexico
 10km radius dated back 65 million years
 Iridium levels are high at the KT boundary layer. Clay in these rocks contain unusually high iridium
which are typically found in meteors
 There are three unusal deposits found at the KT boundary
 Tsunami deposits
 Impact debris (tektites)
 Fullereness in boundary clay indicating high temperature and combustion
Gradual: Permian
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Transgression/regression
o A sudden drop in sea level globally causing geologically unstable oceans and placing immense stress on
marine organisms especially since most organisms at the time were in shallow areas
o Later the sea level rose, again placing stress on species, when they had already adapted to the previous
ocean levels
o This may have also affected rain on a global scale altering rainfall and altering climatic conditions
Volcanic pulses
o Theory suggests that
 Volcanic eruptions lasting up to 10,000 caused a the cooling of the Earth by blocking the sun
 The ash then settled and CO2 caused global warming
 Oceans may have then warmed and became anoxic