REPORT MARK DETERMINATION
SEMESTER
1
2
COMPONENT
2 x Common Tasks (research; common test Term 2)
Practical work e.g. formal reports, experimental
design, investigation follow-up
WEIGHTING
60
25
Class work e.g. informal tests/quizzes, internet
assignments, group activities, problem-solving
activities
15
Common Test Term 3
Australian Schools Science Competition
Practical Examination
Practical work e.g. formal reports, experimental
design, investigation follow-up
20
10
15
20
Class work e.g. informal tests, internet assignments,
group activities, problem-solving activities
5
Semester 2 examination
30
THE
EVOLVIN
G HELIX
BIRTH OF THE UNIVERSE
Where Did It All Begin?
The Big Bang 15-12 bybp
Formation of Solar System 5.0-4.5 bybp
Cosmogenesis
• Cosmology – the study of the universe
• Origin of the Universe – Big Bang, 13.73 bya
• Matter and energy form and the universe
rapidly expands
• ~200 million years of Dark Ages before any
stars formed and light could be emitted from
them
• After another ~200 million years, stars begin
forming galaxies
The Universe Evolves and the Rate of
Expansion Continues to Increase
Courtesy of NASA/WMAP Science Team.
Figure 01: Big Bang to now
The First 100 Seconds Produces
the Subatomic Particles of Matter
Table T01: The first 100 seconds in the life of the universe
Source: Riordan, M. and Zajc, W.A., Scientific American 294 (2006): 24-31.
The Future of the Universe
• Density of ordinary matter in the universe is
extraordinarily low, ~six hydrogen atoms per
cubic meter on average
• If the universe had contained much more
matter, it would have collapsed back on itself
• If the universe had contained much less
matter, it would have expanded forever, but
probably never formed stars
Formation of the solar
system
HTTPS://WWW.YOUTUBE.COM/WAT
CH?V=_MCC8KFACRK
Origin of the Solar System
• Interstellar dust and
gases disturbed by a
nearby supernova
• Gravity causes matter to
coalesce into the sun,
planets, moons,
asteroids, comets, etc.
• Formation requires
more than 100 million
years
Origin of the Solar System
• 5-5.6 bya Solar nebula
• 4.6 bya Sun and accretion disc
• 4.5 bya 4 inner terrestrial planets
4 outer gaseous planets
asteroids, comets, dwarf planets
Figure 03D:
Solidification of
planets
Origin of the Solar
System
Figure 03C: Condensation of nebular
material
Figure 03A: Fragmentation of an
interstellar cloud
Figure 03B: Contraction and
flattening of the solar nebula
Figure 03D: Solidification of planets
Early Earth Is Molten
Origin of the Moon
•
•
•
•
Big Whack
Earth collides with Mars-sized object
Ejected matter coalesces to form the Moon
Oldest Moon rocks are dated to 4.5 bya
The Moon Forms ―
A Major Influence on Living Systems
Theia makes a Big Splash; 30–50 million
years after the origin of the Solar System
What Makes Earth So Special?
• Size of the Sun
• Orbital distance from the
earth to the sun
• Mixture of atomic elements
• Liquid water
• Ozone layer
• Magnetic field
The Earth’s Structure
Figure 04: Section through Earth, which has a radius of 6,357 km
AUSTRALIA – THE TIME
TRAVELLER’S GUIDE
DVD 34
TIME
• studying the Earth leads to the realisation of the
immensity of time
• historical time deals with days, years and centuries
• geological time deals with thousands, millions and
billions of years
Tracks on the Beach
GEOLOGICAL TIME
• Relative time – placing rocks and
geologic events in their proper
sequence over time
• Absolute time – to define the actual
age of a particular geologic event by
radioactive dating methods
The Rock Cycle
Dating Earth’s Rocks and Fossils
• Igneous rocks
– ~65% of the total crust volume
– 17-20% of the exposed crust
• Sedimentary rocks
– ~8% of the total crust volume
– 50-55% of the exposed crust
• Metamorphic rocks
– ~25% of the total crust volume
– 25-30% of the exposed crust
Geologic Time Scale
• First geologic time scale proposed in 1913
by British geologist Arthur Holmes.
• This was soon after the discovery of
radioactivity – using radioisotopes Holmes
estimated the Earth was about 4 billion years
old.
• This was much greater than previously
believed.
Geologic Time Scale
The units of Time represent layers of sedimentary
rocks and fossils that have been identified and
described by geologists over the past two
hundred years.
Geologic Time Scale
• devised so that Time can be understood from the
largest and most general intervals, or units, to
the smallest, most specific intervals.
• originally created using relative time
• structure of the geologic time scale:
Eon, Era, Period, Epoch
Correspondence Among Data Sets
• When several independent lines of evidence are in
agreement, the confidence in the results is greatly
increased.
• Today geologists can use the following evidence to
document the evolution of species and communities
through time:
1. fossils and transitions between fossil types and even
fossil communities (index fossils)
2. evidence from the study of geologic columns and rock
strata
3. evidence from Radiometric and Geomagnetic Dating
4. evidence from Tectonic Plate Movements
Relative Time
A Geologic Column is a vertical diagram of the layers of rock strata at a particular
location. No column at any location on earth contains all the strata from the entire
geologic record. For decades, study of relationships among columns was the only way
sedimentary stratato establish relative dates.
Years of age
500
Tree Rings
8_27
Annual-ring similarities
show correlation
Current year
50
400
100
150
200
Tree
growth
rings
A
B
C
D
A
Sediment layers
with tree logs to
be collected for
dendrochronology
B
C
D
Buried tree
logs
How Fossils are
Formed
• The remains of extinct animals that
persist have escaped the appetites of
scavengers, decomposers, and later
tectonic shifting of the Earth’s crustal
plates in which they reside
• Most surviving fossils are of dead
animals that quickly became covered by
water and escaped the notice of
marauding scavengers
• As more and more silt is deposited over
time, the fossil becomes even more
deeply buried in soil compacted into
hardened rock
• For the fossil held in the rock to be
exposed, the Earth must open either by
fracture or by the eroding action of a
river
How impression fossils form (the most common type)
8_10
Shells
settle on
ocean
floor
Cast forms when mold
is filled in with mineral
water
Rock broken
to reveal
fossil cast
Shells
buried in
sediment
Mold, or cavity,
forms when original
shell material
is dissolved
Rock broken
to reveal external mold
of shell
Methods of Science
Law
• states a relationship that is always the same
under the same conditions
Theory
• serves as a unifying principle that can be
used to explain the laws and the behaviour
and facts about a phenomena
• if it fails to explain new facts it is revised or
rejected
Important Principles of Geology
• Faunal Succession – fossil organisms change
through time and may be used to give relative ages
to strata in different locations
• Faunal Succession - earlier fossil life forms are
simpler than more recent forms, and more recent
forms are more similar to existing forms
– [We now recognize that earlier fossil life forms are not
always simpler than more recent forms.]
Building a Chronology of Fossils
• Each exposure of rocks can be of a different age
from other exposures
• To build up an overall sequence of fossils, various
exposures can be matched where they share similar
sedimentary layers (layers of the same ages)
Stratigraphic Principles
Stratigraphy – branch of Geology that
studies the relationships between rock layers
in order to interpret the history represented by
these rock layers.
Stratigraphy
• Sediment settling out of
water collects at the
bottom of lakes
• As more sediment
collects, the deeper
layers are compacted by
the ones above until they
harden and become rock
• Animal remains become
embedded in these
various layers
Stratigraphy
• Deeper rock forms first
and is older than rock
near the surface
• Logically, fossils in
deeper rock are older
than those above, and
their position within
these rock layers gives
them a chronological age
relative to older (deeper)
or younger (surface)
fossils
Stratigraphy
• Fossil animals and plants occur in sedimentary rocks
deposited on oceanic shorelines, one atop the other
• Subsequent cracks in the Earth’s surface, weathering,
or erosion by a river open these ancient sedimentary
deposits, exposing fossils.
Southern lakes track glaciation
Dating with Lake Varves
Very
little
or no
runoff
Heavy
runoff
into
lake
Ice
Summer
Turbid water
Summer layer
(coarse, thick, and
light-colored)
Winter
Clear water
Winter layer
(fine, thin, and
dark-colored)
Modern Lakes, just count back from present. Fossil pollen track climate.
Correlation
• Matching strata of similar ages in different regions
is called correlation
Correlation
Correlation is a relative geological time
scale.
• It is the process of comparing rocks and
events in adjoining areas to try and
determine
– relative ages of the rocks
– sequence in which the rocks were
layered
• It looks for similar rock types
• It looks for the presence of similar fossils
Correlation
• Principle of fossil succession
• fossil organisms succeed one another in a
recognisable order
• thus any time period is defined by the type
of fossils in it
• Index Fossils - useful for correlation
• existed for a relatively short time
• were widespread and common
Examples of index fossils
• Ammonites were common during the Mesozoic Era (245 to 65 mya),
They were not found after the Cretaceous period, as they went extinct
during the K-T extinction (65 mya).
• Brachiopods (mollusk-like marine animals) appeared during the
Cambrian (540 to 500 mya); some examples still survive.
• Graptolites (widespread colonial marine hemichordates) that lived from
the Cambrian period (roughly 540 to 505 million years ago) to the early to
mid-Carboniferous (360 to 320 million years ago).
• Nanofossils are microscopic fossils (the remains of calcareous
nannoplankton, coccolithophores) from various eras. Nanofossils are very
abundant, widely distributed geographically, and time-specific, because of
their high evolutionary rates. There are enormous numbers of useful
nanofossils, including radiolarians and foraminifera. Nanofossils are the
primary method of dating marine sediments.
• Trilobites were common during the Paleozoic Era (540 to 245 mya);
about half of the Paleozoic fossils are trilobites. They evolved at the
beginning of the Paleozoic Era and went extinct during the late Permian
period (248 million years ago).
Index Fossils for Major Epochs
Index Fossils
• After careful study at many well-dated sites, paleontologists can confirm
that certain fossils occur only at restricted time horizons (in specific rock
layers)
• These distinctive index fossils are diagnostic fossil species used to date
rocks in new exposures
• In this example, the absence of index fossils confirms that layer B does not
exist at the third location
• Perhaps rock-forming processes never reached the area during this time
period, or the layer was eroded away before layer C formed
CORRELATION OF ROCK LAYERS
• Matching strata of
similar ages in
different regions is
called correlation
Correlation of Layers
Correlation Activity – Example A
Correlation - Example B
Important Principles of Geology
• Superposition - strata, if undisturbed, form a
vertical time line, whether sedimentary or
volcanic/igneous or a mixture; younger rocks are on
top of older
• Original Horizontality - sediments form horizontal
layers; volcanic/igneous material may or may not;
any tipping or bending must have occurred later
• Cross-Cutting Relationships - when strata break and
faults develop, the faults are younger than the
surrounding strata and any material which fills into
a fault is younger still
Important Principles of Geology
• Intrusive Relationships - when volcanic/igneous
material penetrates into sedimentary strata, it is
younger
• Inclusions - newly formed strata (sediments or
igneous flows) may surround older material such as
gravels, cobbles, or boulders
Stratigraphic Principles
Law of Superposition
• in an undisturbed
sequence of
sedimentary rock
layers, each layer of
rock is older than the
layer above it and
younger than the rock
layer below it.
Younger
Older
The Grand Canyon
Law of Superposition
Stratigraphic column on
north shore of Isfjord,
Svalbard, Norway.
Since there is no
overturning, the rock at
the bottom is older than
the rock on the top by the
Principle of Superposition.
Stratigraphic Principles
Law of Original Horizontality
• sediments like sand, gravel and mud, are
deposited on the earths surface as flat,
continuous sheets
• if they are no longer flat or are irregular,
then they necessarily have had something
happen to them after they formed.
Stratigraphic Principles
The Law of
Original
Horizontality says
that those layers
were first deposited
flat, and later tilted.
For example, in the Grand Canyon, about ¾ of the way below the rim, towards the river,
there are a series of tilted rock layers
Stratigraphic Principles
Law of Cross-cutting Relationships
– the rock layers that are cut by another geologic
feature must have formed before the feature that
cuts through them
Law of Cross-cutting Relationships
An igneous
intrusion would
have to be
younger than the
rock that was
already there
volcanic dyke
Law of Cross-cutting Relationships
If a rock is cut by a fault, the rock had to be there first and
then cut later
fault
Faulting and Erosion
HTTP://WWW.WWNORTON.COM/C
OLLEGE/GEO/ANIMATIONS/GEOLO
GIC_HISTORY.HTM
Correlation of strata
Sections are incomplete
Match with fossils and lithology
Data from five sites in the southwest United States: overlapping time intervals allow
paleontologists to build a chronology of fossils greater than that at any single site
Law of Cross-cutting Relationships
Erosion into a rock layer (like erosion of a valley
or gulley) would have to occur after the rock
layers the erosion cuts into had been formed
Unconformity
• discontinuity in the geological history of
an area
• may be caused by extensive weathering
and erosion of previously deposited
layers
• a gap in time is produced in the rock
record
Formation of an Unconformity
Unconformity
Unconformity
500 million year old
sandstone
unconformity
1 billion year old granite
Formation of an angular unconformity
Stratigraphic Principles
Folding of rock layers
Stratigraphic Principles
Folding of rock
layers
Geological Profile Diagram
limestone
Youngest event
__________
__________
__________
granite
Oldest event
Geological Profile Diagram
limestone
Youngest event
B
C
A
granite
Oldest event
Geological Profile Diagram
Youngest event
__________
__________
__________
__________
__________
Oldest event
Geological Profile Diagram
Youngest event
A
D
C
B
E
Oldest event
Geological Time Intervals
• The Earth’s history, from its beginnings ~4.6 billion
years ago, is divided into four major eons of unequal
length:
1. Hadean
2. Archean
3. Proterozoic
4. Phanerozoic
• Each eon is divided into periods, and periods into
epochs
The Geologic Time Scale
Youngest
Oldest
Geologic Time
• The Universe is
approximately 14 billion
years old.
• Cosmic gases coalesced
under gravity’s pull to create
the solar system and Earth
approximately 4.6 billion
years ago
• Life remained rare, simple
and small (“microbial”) until
the Cambrian period, or
slightly earlier, when the
various metazoans appeared,
0.54 Billion Years Ago.
The History of Life
Now Runs Some
4.6 Billion Years
> 99% of all
species are
already extinct!
Continental
Laurasia &
Drift
Gondwana
Pangaea
• Changing continental positions through most of the
Phanerozoic era. Time, in millions of years, is approximate.
Absolute Time
A Geologic Column is a vertical diagram of the layers of rock strata at a particular
location. No column at any location on earth contains all the strata from the entire
geologic record. For decades, study of relationships among columns was the only way
sedimentary stratato establish relative dates.
Radioactive Decay
Radioactive Decay
Radioactive Decay
Radiometric Age Determinations
of the Earth
• the age of the Earth is thought to be about 4.6
billion years
• based on the radioisotope dates obtained from
meteorites and samples of rocks collected on
the moon (assumed to have formed at the same
time)
ZIRCON CRYSTALS AND
RADIOMETRIC DATING
http://www.earth-time.org/movs.html
A Closer Look at Radiometric Dating
Parent and Daughter Isotopes
Used in Radiometric Dating
Radiometric Dating
Radiometric
Dating
• (a) Sand flows regularly from one state (upper portion) to another (lower portion)
in an hourglass. The more sand in the bottom, the more time has passed. By
comparing the amount of sand in the bottom with that remaining in the top and by
knowing the rate of flow, we can calculate the amount of time that has elapsed
since the flow in an hourglass was initiated.
• Similarly, knowing the rate of transformation and the ratios of product to original
isotope, we can calculate the time that has passed for the radioactive material in
rock to be transformed into its more stable product.
Radiometric
Dating
• (b) Half-life. It is convenient to visualize the rate of radioactive decay in terms of
half-life, the amount of time it takes an unstable isotope to lose half its original
material. Shown in this graph are successive half-lives. The amount remaining in
each interval is half the amount present during the preceding interval.
• (c) A radioactive material undergoes decay, or loss of mass, at a regular rate that is
unaffected by most external influences, such as heat and pressure. When new rock
is formed, traces of radioactive materials are captured within the new rock and
held along with the product into which it is transformed over the subsequent
course of time.
• By measuring the ratio of product to remaining isotope, paleontologists can date
the rock and thus date the fossils it contains.
Carbon Dating - Dating with carbon-14
• Half-life only 5730 years
• Used to date very young rocks
• Carbon-14 is produced in the upper
atmosphere
• Useful tool for geologists who study
very recent Earth history
Carbon-14
Atoms split into
smaller 8_24
particles,
among them neutrons
Cosmic rays
bombard
atmospheric atoms
Neutrons strike
nitrogen atoms
Nitrogen atoms lose a
proton and becomes
carbon-14
C-14 mixes with atmospheric oxygen
to produce CO2
C-14 absorbed
by living
organisms
CO2 taken up
by plants
CO2 dissolved
in water
C-14 intake ceases when organism
dies; C-14 concentration decreases
Carbon Isotopes
• While alive, organisms
accumulate both ordinary
carbon (C12) and its unstable
isotope carbon-14 (C14)into
their tissues in proportion to
their availability in the
atmosphere
• During its lifetime, an organism
continually replenishes its
supply of C14 by photosynthesis,
respiration and absorbing or
ingesting nutrients
Radiocarbon
Dating
• When the organism dies, stable C12 persists, but unstable
C14 decays to N14 at a constant rate and is slowly lost from
the fossil
• To measure the amount of radiocarbon left in a fossil,
scientists burn a small piece to convert it into carbon
dioxide gas
• Radiation counters are used to detect the electrons given
off by decaying C14 as it turns into nitrogen
Radiocarbon (C14) Dating
• The more time that passes, the
more C14 is lost from the fossil,
thereby changing the
proportion of C14 to C12 with
the passage of time
• Consequently by measuring
the proportion of C12 to the
remaining C14, scientists are
able to calculate the geologic
age of the fossil
C14 / C12
Evolution
Charles Darwin (1809-1882)
• born into a privileged, powerful family
• studied medicine and theology – intended to be
ordained into the Church of England
• in 1831 was invited to travel around the world on the
HMS Beagle surveying plant and animal life in the
southern hemisphere
• compared the religious theory he had been taught
with reality and could not reconcile the two
• proposed his theory of natural selection in On The
Origin of Species published in 1859
DARWIN’S DANGEROUS IDEAS –
PBS DOCUMENTARY
http://www.youtube.com/watch?v=MCOc7Xqj-kQ
Natural Selection
Natural selection is based on two points:
1. The reproductive capacity of organisms exceeds the
carrying capacity of the environment
2. Variation in organisms makes survival a non-random
event
–
–
Some variants are more likely to survive in a given environment
of the organisms that are produced the most “fit for the
environment” survive, reproduce and pass their characteristics on
to the next generation
Darwin’s Contributions to Geology
and Paleontology
• Darwin had training as a geologist
• Darwin made extensive observations and
collections of strata and their fossils while on
excursion from the Beagle
• Darwin studied coral reefs and atolls and
explained their formation by incremental growth
• Darwin linked geographical distribution of
organisms to the geology of their locations
Darwin’s Evidence
for Evolution
• Darwin’s The Origin of Species (1859)
– documents that fact that evolution has occurred
– gives examples of artificial and natural selection to
explain the mechanism of evolution
– includes considerable evidence from comparative
anatomy and comparative embryology
– invokes Uniformitarianism to give time for gradual
change
– relies very little on the fossil record, a record still quite
meager in the 1850s
DARWIN – DECENT WITH
MODIFICATION
- WE'VE DEFINED EVOLUTION AS
DESCENT WITH MODIFICATION FROM A
COMMON ANCESTOR.
HTTPS://WWW.YOUTUBE.COM/WATCH?
V=FARLFSYMKEY
The Voyage Of The Beagle
England
Cape Verde
Islands
Tahiti
Galapagos
Islands
South
America
Cocos
Islands
Rio de
Jeneiro
Falkland
Islands
Mauritius
Sydney
Australia
New
Zealand
The Logic Of Darwin
• The fossils in South America were different from the
animals that lived there now, but some seemed to be
related in some way
• If fossils were a record of the past then there must
have been change (evolution) between the past and
now
• Change is happening slowly thus to get change must
have taken a long time
• The rock strata took a long time to form thus lots of
time is available for evolution
• Organisms evolved over LONG periods of time
Evolution by Natural Selection
• in any population of organisms there are
differences (variation)
• in any generation there are offspring that
do not survive and reproduce – their
features are removed from the population
Evolution by Natural Selection
• organisms that survive and reproduce are
well adapted to the environment – they have
favourable variations
• favourable variations are passed on to
offspring and become more common in the
population
• “survival of the fittest for the environment”
EVIDENCE FOR EVOLUTION
The Fossil Record
Chronological appearance of organisms - bacteria invertebrates - fish - amphibians - reptiles - birds mammals, with the occasional evidence of
intermediate forms (evolutionary transitions) between
groups of organisms
Comparative Anatomy
Comparative Embryology
Above are sketches of embryos of the tortoise, chicken,
pig, fish, human, cow, salamander and rabbit at the
same stage in development.
Which one is the human embryo?
Comparative Embryology
The Mechanism Of Evolution
• Darwin was not the first to propose evolution,
Lamarck and others had done it before him
• Darwin’s real contribution was a credible
mechanism for evolution
- Natural Selection
“I have called this principle, by which each
slight variation, if useful, is preserved, by
the term Natural Selection. “
- Charles Darwin, The Origin of Species
Tree of Life
Common
descent: the
idea that all living
things share
common
ancestors
Darwin and Naturalism
• Naturalism - The belief that all phenomena
can be explained in a rational way, in terms
of natural causes, without invoking the
supernatural
• Because Darwin proposed a natural cause
(natural selection) for organisms’ origin his
theory is considered scientific
• religious accounts invoking the supernatural
are not
Darwin and Evolution
A few million years ago one species of finch
migrated to the Galapagos from the mainland of
South America - several different species then
evolved due to variations in the environment