SEMESTERCOMPONENTWEIGHTING 1 2 x Common Tasks (research; common test Term 2)60 Practical work e.g....

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SEMESTER COMPONENT WEIGHTING

2 x Common Tasks (research; common test Term 2)

Practical work e.g. formal reports, experimental design, investigation follow-

Class work e.g. informal tests/quizzes, internet assignments, group activities,

problem-solving activities

Common Test Term 3 20Australian Schools Science Competition 10

Practical Examination 15Practical work e.g. formal reports,

experimental design, investigation follow-up

Class work e.g. informal tests, internet assignments, group activities, problem-

solving activities

Semester 2 examination 30

REPORT MARK DETERMINATION

THE EVOLVI

NG 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

Figure 01: Big Bang to nowCourtesy of NASA/WMAP Science Team.

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/WATCH?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

• 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

Figure 03A: Fragmentation of an interstellar cloud

Figure 03B: Contraction and flattening of the solar nebula

Figure 03C: Condensation of nebular material

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 ScaleThe 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

strata3. evidence from Radiometric and Geomagnetic Dating4. evidence from Tectonic Plate Movements

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 to establish relative dates.sedimentary strata

Relative Time

Sediment layerswith tree logs tobe collected fordendrochronology

Annual-ring similaritiesshow correlation Current year

Years of age

50 100 150 200400

Buried treelogs

Treegrowthrings

Tree Rings

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

Rock brokento reveal external moldof shell

Rock brokento revealfossil cast

Shellsburied insediment

Mold, or cavity,forms when originalshell materialis dissolved

Cast forms when moldis filled in with mineralwater

Shellssettle onoceanfloor

How impression fossils form (the most common type)

Methods of Science

Law• states a relationship that is always the

same under the same conditionsTheory• 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.

Turbid water

Heavyrunoffintolake

Very little or norunoff

Summer layer(coarse, thick, andlight-colored)

Clear water

Winter layer(fine, thin, and dark-colored)

Summer Winter

Dating with Lake Varves

Modern Lakes, just count back from present. Fossil pollen track climate.

Southern lakes track glaciation

Correlation• Matching strata of similar ages in different regions

is called correlation

CorrelationCorrelation 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 correlationhttp://www.uwsp.edu/geo/faculty/ozsvath/images/stratigraphy.jpg

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 PrinciplesLaw 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.

The Grand Canyon

Younger

Law of SuperpositionStratigraphic 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.

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.

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

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

volcanic dyke

An igneous intrusion would have to be younger than the rock that was already there

Law of Cross-cutting Relationships

If a rock is cut by a fault, the rock had to be there first and then cut later

HTTP://WWW.WWNORTON.COM/COLLEGE/GEO/ANIMATIONS/GEOLOGIC_HISTORY.HTM

Faulting and Erosion

Correlation of strata

Sections are incompleteMatch 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 RelationshipsErosion 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

1 billion year old granite

500 million year old sandstone

unconformity

Unconformity

Formation of an angular unconformity

Folding of rock layers

Geological Profile Diagram

Youngest event

__________

Oldest eventgranite

limestone

Youngest event

Oldest eventgranite

limestone

Youngest event

__________

Oldest event

Geological Profile DiagramYoungest event

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. Archean3. Proterozoic 4. Phanerozoic • Each eon is divided into periods, and periods into

epochs

The Geologic Time ScaleYoungest

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 LifeNow Runs Some4.6 Billion Years

> 99% of allspecies arealready extinct!

Continental Drift

• Changing continental positions through most of the Phanerozoic era. Time, in millions of years, is approximate.

Laurasia &Gondwana

Pangaea

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 to establish relative dates.sedimentary strata

Absolute Time

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

RadiometricDating

• (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.

RadiometricDating

• (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

8_24Atoms split intosmaller particles,among them neutrons

Neutrons strikenitrogen atoms

Nitrogen atoms lose aproton and becomescarbon-14

C-14 mixes with atmospheric oxygento produce CO2

CO2 taken upby plants

C-14 absorbedby livingorganisms

CO2 dissolvedin water

C-14 intake ceases when organismdies; C-14 concentration decreases

Cosmic raysbombardatmospheric atoms

Carbon-14

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

RadiocarbonDating

• 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 DOCUMENTARYhttp://www.youtube.com/watch?v=MCOc7Xqj-kQ

Natural SelectionNatural 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 Evidencefor 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

GalapagosIslands

Falkland Islands

The Voyage Of The Beagle

SouthAmerica

Rio deJeneiro

England

Cape Verde Islands

AustraliaSydney

New Zealand

Mauritius

CocosIslandsTahiti

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

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