2.2 &2.3 Fossils and 2.2 &2.3 Fossils and Geological time scaleGeological time scale

Think About It . . . Think About It . . . Can you name any Can you name any

dinosaurs?dinosaurs? Do you know what Do you know what

they looked like or they looked like or how they moved?how they moved?

Scientists have been Scientists have been able to tell us many able to tell us many things about things about organisms (such as organisms (such as dinosaurs) that lived dinosaurs) that lived millions of years ago.millions of years ago.

How do scientists How do scientists learn about these learn about these organisms if they’ve organisms if they’ve never seen them?never seen them?

Fossils!Fossils! Fossils = the preserved remains or Fossils = the preserved remains or

imprints/evidence of an organism that lived imprints/evidence of an organism that lived long ago- either in part or a whole organismlong ago- either in part or a whole organism

There are 4 Types of fossilsThere are 4 Types of fossils

Types of FossilsTypes of Fossils

OriginalOriginal

ReplacementReplacement

Carbon FilmCarbon Film

Indirect FossilsIndirect Fossils

OriginalOriginal- Organism - Organism preserved and original preserved and original chemical structure chemical structure remains almost the remains almost the samesame

E.g complete Skeleton, E.g complete Skeleton, bones or tooth or shellbones or tooth or shell

Made of calcium Made of calcium carbonate resistant to carbonate resistant to decaydecay

Replacement FossilsReplacement Fossils Forms when part of the Forms when part of the

organisms is chemically organisms is chemically changedchanged

Takes a long timeTakes a long time Usually the calcium Usually the calcium

carbonate turns into carbonate turns into silica- silicon dioxide- silica- silicon dioxide- like sand.like sand.

Sometimes it turns into Sometimes it turns into opal! Another form of opal! Another form of silicasilica

If the material If the material being replaced is being replaced is wood- it is referred wood- it is referred to as petrifiedto as petrified

PetrificationPetrification Minerals can replace Minerals can replace

tissues (organs, muscles, tissues (organs, muscles, skin)skin)

In animals, minerals fill the In animals, minerals fill the tiny spaces in the hard tiny spaces in the hard tissues (like bone)tissues (like bone)

In trees, minerals replace In trees, minerals replace the wood, so the wood the wood, so the wood becomes rock.becomes rock.

Carbon Film & Indirect Carbon Film & Indirect FossilsFossils

Occur when dead Occur when dead bodies partially decay bodies partially decay leaving thin black leaving thin black layers of carbonlayers of carbon

Also called carbon Also called carbon trace fossilstrace fossils

Still in the shape of Still in the shape of the organism and the organism and shows fine detailshows fine detail

Coal is made this way.Coal is made this way.

Indirect fossils are not Indirect fossils are not part of the organism part of the organism itself-but preserved itself-but preserved remains of the imprints remains of the imprints of the bodies i.e of the bodies i.e footprints, or tracks, footprints, or tracks, burrows and dung!!! burrows and dung!!! (trace fossils)(trace fossils)

Moulds are imprints of Moulds are imprints of the outside of an the outside of an organism- it’s a negative organism- it’s a negative imageimage

Examples of Trace FossilsExamples of Trace Fossils Burrows (shelters made by animals that Burrows (shelters made by animals that

bury themselves in the sediment) may be bury themselves in the sediment) may be filled with sediment and preserved.filled with sediment and preserved.

““Caprolites” = dung (“poop”) that is Caprolites” = dung (“poop”) that is fossilized.fossilized.

What is a negative Image?What is a negative Image? It is the space where It is the space where

there is no bodythere is no body Mollusc shells Mollusc shells

commonly form commonly form mouldsmoulds

-shell is covered with -shell is covered with sediment, turns into sediment, turns into rock, original shell rock, original shell dissolved by acids-dissolved by acids-leaves the imprint.leaves the imprint.

Common in the Common in the ocean- crabs, ocean- crabs, lobsters and lobsters and prawns- and prawns- and ancient ones ancient ones called trilobitescalled trilobites

Internal moulds and castsInternal moulds and casts

If the mould is of the If the mould is of the inside of an inside of an organism- it could be organism- it could be if a snail shell fills up if a snail shell fills up with mud-hardens with mud-hardens and turns to rock-and turns to rock-and the shell is then and the shell is then decayed awaydecayed awayMaking a carbon fossil &/or Making a carbon fossil &/or bendy bone activity 41bendy bone activity 41

CASTS- when an CASTS- when an organism in rock organism in rock decays-the space in decays-the space in the rock fills with soil the rock fills with soil which then turns into which then turns into rock-leaving a copy rock-leaving a copy of the outside of the of the outside of the organism –positive organism –positive image and three image and three dimensionaldimensional

Moulds & CastsMoulds & Casts Mould = the print/impression left in Mould = the print/impression left in

sediment/rock where the plant/animal was sediment/rock where the plant/animal was buried.buried.

Cast = forms when sediment fills a mould and Cast = forms when sediment fills a mould and becomes rock.becomes rock.

Both can show what the inside or outside of Both can show what the inside or outside of an organism looked like.an organism looked like.

Preserving Environments- Preserving Environments- Fossils in RocksFossils in Rocks

As we have said………As we have said……… Usually when an organism dies, Usually when an organism dies,

it begins to decay right away. it begins to decay right away. But sometimes organisms are But sometimes organisms are

buried by sediment when they die. buried by sediment when they die. Sediment can preserve the organism.Sediment can preserve the organism. Hard parts (shells, teeth, bones) are preserved more Hard parts (shells, teeth, bones) are preserved more

often than soft parts (skin, organs).often than soft parts (skin, organs). These parts become fossils when the sediment hardens These parts become fossils when the sediment hardens

to form a sedimentary rock. to form a sedimentary rock. (see Pearsons pg 40)(see Pearsons pg 40)

Fossils in AmberFossils in Amber Sometimes organisms (such as insects, frogs, Sometimes organisms (such as insects, frogs,

and lizards) are caught in sticky tree sap.and lizards) are caught in sticky tree sap. If the sap hardens around the insect, a fossil is If the sap hardens around the insect, a fossil is

created.created. Hardened tree sap is Hardened tree sap is

called “amber.” called “amber.”

Frozen Fossils-PermafrostFrozen Fossils-Permafrost Ice and cold temperatures slow down decay.Ice and cold temperatures slow down decay. Fossils can be preserved in blocks of ice.Fossils can be preserved in blocks of ice. Fossils of woolly mammoths, relatives of Fossils of woolly mammoths, relatives of

elephants that went extinct 10,000 years elephants that went extinct 10,000 years ago, have been found in ice.ago, have been found in ice.

One was found One was found of a baby mammothof a baby mammoth in 2007 in Russiain 2007 in Russia

Fossils in Asphalt/TarFossils in Asphalt/Tar In some places, asphalt In some places, asphalt

can bubble and form sticky can bubble and form sticky pools of tar.pools of tar.

The La Brea Tar Pits in L.A. The La Brea Tar Pits in L.A. are at least 38,000 years are at least 38,000 years old.old.

These pools have trapped These pools have trapped and preserved many and preserved many different organisms, like different organisms, like the saber-toothed cats & the saber-toothed cats & dire wolves.dire wolves.

From these fossils From these fossils scientists have learned scientists have learned about what California was about what California was like 10,000 to 40,000 years like 10,000 to 40,000 years ago.ago.

EVIDENCEEVIDENCE

Fossils in PeatFossils in Peat Peat is the partly Peat is the partly

decomposed remains decomposed remains of plantsof plants

Usually in Usually in swamps/bogsswamps/bogs

Not much oxygen in Not much oxygen in the lower layersthe lower layers

Therefore soft tissue Therefore soft tissue has a chance to be has a chance to be preservedpreserved

Peat is acidic and Peat is acidic and dissolves the hard dissolves the hard minerals making them minerals making them soft- softens the bony soft- softens the bony partsparts

DRY AIR- since bacteria DRY AIR- since bacteria need moisture to grow need moisture to grow and decay things- very and decay things- very dry air can also dry air can also preserve things-preserve things-mummificationmummification

What Can Fossils Tell Us?What Can Fossils Tell Us? Fossils can show scientists 3 main things:Fossils can show scientists 3 main things:

1)1) The kind of organism that lived in the pastThe kind of organism that lived in the past

2)2) How the environment has changed (ex: How the environment has changed (ex: forest fossils found in Antarctica show the forest fossils found in Antarctica show the climate was much warmer in the past)climate was much warmer in the past)

3)3) How organisms have changedHow organisms have changed

Index FossilsIndex Fossils Fossils of certain types of Fossils of certain types of

organisms can be found all over organisms can be found all over the world.the world.

But these fossils are found only But these fossils are found only in rock layers of a certain age.in rock layers of a certain age.

These are called index fossils.These are called index fossils. When scientists see a specific When scientists see a specific

index fossil, they know right index fossil, they know right away how old it is away how old it is

Ex: When scientists find Ex: When scientists find PhacopsPhacops in a rock layer, they in a rock layer, they know the rock layer is 400 know the rock layer is 400 million yrs old.million yrs old.

Famous Fossil SitesFamous Fossil Sites

Ediacara-Flinders RangesEdiacara-Flinders Ranges La Brea tar pits in Los AngelesLa Brea tar pits in Los Angeles Burgess Shale in CanadaBurgess Shale in Canada Chengjiang in ChinaChengjiang in China Solnhofen in GermanySolnhofen in Germany

Human Endeavour- pg 45 PearsonsHuman Endeavour- pg 45 Pearsons

How Old Is It?- dating How Old Is It?- dating techniques!!!!techniques!!!!

To understand the To understand the history of the history of the Earth, scientists Earth, scientists have put fossils in have put fossils in order based on order based on their ages.their ages.

They use relative They use relative dating and dating and absolute dating absolute dating methods methods

Relative DatingRelative Dating

This technique This technique compares the compares the age of one fossil age of one fossil with another to with another to determine which determine which is olderis older

Relies on two facts!Relies on two facts! Sedimentary rock Sedimentary rock

forms in layersforms in layers

Fossils are the Fossils are the same age as the same age as the rocks in which rocks in which they are foundthey are found

Sedimentary rockSedimentary rock Forms in layers Forms in layers

called stratacalled strata Sediment always Sediment always

settles –so oldest settles –so oldest strata is the strata is the bottom layerbottom layer

Helps to determine Helps to determine which lived before which lived before whatwhat

NOTE: due to folding NOTE: due to folding etc. of rock layers the etc. of rock layers the bottom layer may not bottom layer may not always be the oldest always be the oldest in an areain an area

Index-FossilsIndex-Fossils Already mentionedAlready mentioned As most species didn’t As most species didn’t

live long- only found in live long- only found in a narrowband of rock a narrowband of rock strata in any one strata in any one locationlocation

Therefore it is said that Therefore it is said that fossils of the same type fossils of the same type must mean they are must mean they are similar in age and the similar in age and the age of the rockage of the rock

To be an index fossilTo be an index fossil The species must The species must

have been have been widespreadwidespread

Lived in a narrow Lived in a narrow time frametime frame

Have been abundantHave been abundant Be easy to identifyBe easy to identify Comparing layers is Comparing layers is

called stratigraphycalled stratigraphy Pg 49-PearsonsPg 49-Pearsons

Fluorine DatingFluorine Dating Compares the amount Compares the amount

of fluorine found in of fluorine found in different bones in the different bones in the same rocksame rock

Bones absorb fluorine Bones absorb fluorine from waterfrom water

Happens slowly and Happens slowly and depends on the depends on the fluorine content of the fluorine content of the waterwater

Has been helpful Has been helpful in exposing in exposing hoax’s from the hoax’s from the pastpast

Research- Research- Piltdown Man…Piltdown Man…see pg 50 see pg 50 PearsonsPearsons

Absolute Dating- radioactive Absolute Dating- radioactive datingdating

Considered Considered absolute if it gives absolute if it gives the actual age of the actual age of a rock or fossila rock or fossil

One method is One method is radioactive dating radioactive dating and the other is and the other is tree ringstree rings

Radioactive uses the Radioactive uses the natural rate of decay natural rate of decay of radioactive of radioactive isotopesisotopes

Isotopes are atoms Isotopes are atoms with a different with a different number of neutrons number of neutrons and different atomic and different atomic massesmasses

Carbon…Carbon…

Has three isotopesHas three isotopes All have six protonsAll have six protons Carbon 14 is Carbon 14 is

radioactiveradioactive Radioactive Radioactive

isotopes decay at a isotopes decay at a known rateknown rate

Releasing particles Releasing particles that are radioactivethat are radioactive

We can measure We can measure thisthis

The elements that The elements that decay then form new decay then form new elements –the elements –the amount of which we amount of which we can measure toocan measure too

Decay allows us Decay allows us to estimate the to estimate the age the rock was age the rock was laid downlaid down

Pg 51 PearsonsPg 51 Pearsons

Tree RingsTree Rings A useful method of A useful method of

absolute dating is absolute dating is tree ringstree rings

This method is This method is accurate to several accurate to several thousands years thousands years agoago

You count the rings You count the rings of growth in woody of growth in woody trunks of treestrunks of trees

Many trees add outer Many trees add outer layers each yearlayers each year

This leaves a line in This leaves a line in the trunkthe trunk

When you cut down When you cut down and through a tree and through a tree you can see these you can see these rings and count themrings and count them

These are still visible These are still visible in fossilised in fossilised trees/woodtrees/wood

Pop QuizPop Quiz What is a fossil?What is a fossil?

The remains or imprints of an organism that The remains or imprints of an organism that lived long ago.lived long ago.

What are 5 different ways fossils can form?What are 5 different ways fossils can form? In rock, amber, ice, asphalt, or by In rock, amber, ice, asphalt, or by

petrificationpetrification What 3 things can fossils tell us?What 3 things can fossils tell us?

1)1) The kind of organism that lived in the pastThe kind of organism that lived in the past2)2) How the environment has changed How the environment has changed 3)3) How organisms have changedHow organisms have changed

Who loves fossilized poop (caprolites)?Who loves fossilized poop (caprolites)? We all do!We all do!

Geological time scaleGeological time scale

When palaeontologists look at the When palaeontologists look at the sequence of different fossil species found sequence of different fossil species found in rock strata throughout the world- they in rock strata throughout the world- they produce a time scaleproduce a time scale

The Geological time scale- a record of The Geological time scale- a record of past life and geologypast life and geology

Involves relative and absolute dates;Involves relative and absolute dates; Relative-using stratigraphy and index fossils a continuous Relative-using stratigraphy and index fossils a continuous

sequence of rock strata back into the past was constructed sequence of rock strata back into the past was constructed AND we have looked at absolute priorAND we have looked at absolute prior

Students –copy of page 57Students –copy of page 57 The earliest organisms -not all time The earliest organisms -not all time

periods have fossil due to the size of the periods have fossil due to the size of the organisms or how delicate they were.organisms or how delicate they were.

OR…..no life existed then?OR…..no life existed then? First life is assumed to be bacteria-or First life is assumed to be bacteria-or

single celled organismssingle celled organisms Earliest evidence are fossils from water-Earliest evidence are fossils from water-

cyanobacteria-formed structures called cyanobacteria-formed structures called stromatolites-lots in Western Australia-world heritage stromatolites-lots in Western Australia-world heritage sitessites

If you cut a stromatolite in half you can see the If you cut a stromatolite in half you can see the black carbon layers-or carbon film fossils of the black carbon layers-or carbon film fossils of the

bacteria that formed the layersbacteria that formed the layers

Stromatolites are laminated fossils formed by blue-green Stromatolites are laminated fossils formed by blue-green algae and sediment. Sediment sticks to the surface of the algae and sediment. Sediment sticks to the surface of the living algae, forming a crust. In turn, the algae grows through living algae, forming a crust. In turn, the algae grows through the sediment to form a new layer of living matter. A newthe sediment to form a new layer of living matter. A newfilm of sediment sticks to the algae and so on. The resulting film of sediment sticks to the algae and so on. The resulting structure looks like a mound. In cross section, structure looks like a mound. In cross section, each layer can be seen.each layer can be seen.

Stromatolites are the most abundant fossils known from theStromatolites are the most abundant fossils known from thePrecambrian. They are less common in the Paleozoic, perhaps Precambrian. They are less common in the Paleozoic, perhaps because snail-like predators began to graze on the algae.because snail-like predators began to graze on the algae.Geologic Range: Archean to Recent Geologic Range: Archean to Recent

Cross section-stromatolitesCross section-stromatolites

Vertebrate fossils historyVertebrate fossils history Animals with backbones!-earliest fossils Animals with backbones!-earliest fossils

pre-cambrian era in Chinapre-cambrian era in China First land plants-Cooksonia-Silurian period First land plants-Cooksonia-Silurian period

later than the vertebrate fossils- believed later than the vertebrate fossils- believed it was these plants that allowed it was these plants that allowed movement from the water to land for life movement from the water to land for life i.e insects and vertebrates were found i.e insects and vertebrates were found just after this time periodjust after this time period

Lobe –finned fish- Devonian Lobe –finned fish- Devonian period-so called period-so called as had bones in their fins like land animalsas had bones in their fins like land animals

Lungfish-or Lungfish-or NeoceratodusNeoceratodus forsteriforsteri.-the QLD lungfish.-the QLD lungfish

Assumed that these fish had lungs Assumed that these fish had lungs like the modern day lung fish…like the modern day lung fish…

Land VertebratesLand Vertebrates

First fossils- amphibians called First fossils- amphibians called tetrapods- four limbstetrapods- four limbs

Living tetrapods are: amphibians, Living tetrapods are: amphibians, reptiles, birds and mammalsreptiles, birds and mammals

There are still lots of gaps in the There are still lots of gaps in the fossil record? …..what does this fossil record? …..what does this mean???????mean???????

Birds….Birds….

Birds appear in the Jurassic periodBirds appear in the Jurassic period Shared features with small dinosaurs Shared features with small dinosaurs

called theropodscalled theropods Dinosaurs with feathers…interesting!Dinosaurs with feathers…interesting! Archaeopteryx –ancient wing, early bird Archaeopteryx –ancient wing, early bird

fossil, found in Germany-had feathers fossil, found in Germany-had feathers and a wish bone.and a wish bone.

Students look up this fossil and compare to the Students look up this fossil and compare to the skeletal structure of a modern pigeon/birdskeletal structure of a modern pigeon/bird

Humans…..Humans…..

Order-primates…mammalsOrder-primates…mammals Along with apes and monkeys and Along with apes and monkeys and

gibbons!gibbons! Earliest Homo sapien fossils believed Earliest Homo sapien fossils believed

to be 130 000 years old.to be 130 000 years old. ? ? Practical vertebrate skeletonsPractical vertebrate skeletons