FOSSILSFOSSILS

FossilsFossils remains or imprints of an organism that lived remains or imprints of an organism that lived

long agolong ago Formed 5 ways ….Formed 5 ways ….

1) In Rocks1) In Rocks

Dead organism is buried Dead organism is buried in sedimentin sediment

2) Amber2) Amber hardened tree saphardened tree sap

3) Frozen3) Frozen Found in blocks of iceFound in blocks of ice

4) Petrification4) Petrification Minerals replace tissues Minerals replace tissues

and become rockand become rock

5) Asphalt/Tar5) Asphalt/Tar La Brea Tar Pits in L.A. La Brea Tar Pits in L.A.

are at least 38,000 years are at least 38,000 years old.old.

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

Types of FossilsTypes of Fossils

1) Trace Fossils1) Trace Fossils Clues made by an Clues made by an

organism, but do not organism, but do not include parts of the include parts of the organism’s bodyorganism’s body

Other Examples of Trace Other Examples of Trace FossilsFossils

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.

2) Molds2) Molds Mold = the print/impression left in Mold = the print/impression left in

sediment/rock where organism was buried.sediment/rock where organism was buried.

3) Cast3) Cast

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

How it is formedHow it is formed

http://www.oum.ox.ac.uk/thezone/fossils/intro/form.htm

http://www.brainpop.com/science/diversityoflife/fossils/

What Can Fossils Tell Us?What Can Fossils Tell Us?1)1) The kind of organismThe kind of organism

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 changed (evolved)How organisms have changed (evolved)

How Old Is It?How Old Is It? 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

Index FossilsIndex Fossils fossils are found only in rock fossils are found only in rock

layers of a certain age.layers of a certain age. 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.

Fossil ObservationFossil ObservationFossil Name Drawing Type / Age

Whale EvolutionWhale Evolutionbased on fossilsbased on fossils

Ocean adapted Ocean adapted mammalsmammals

Embryos of several Embryos of several whales have well-whales have well-developed rear legs developed rear legs that disappearthat disappear

Fossils of modern Fossils of modern whales are not so whales are not so “modern”“modern”

How did whales get here?How did whales get here?

Primitive whales (#1) found in Primitive whales (#1) found in rocks about 36 myarocks about 36 mya

Place Mesonychid at 55 mya levelPlace Mesonychid at 55 mya level Pakicetus (#3) was found in sediment Pakicetus (#3) was found in sediment

50 million years old.50 million years old. Basilasaurus (#4) fossils found – 37 myaBasilasaurus (#4) fossils found – 37 mya Rodhocetus fossils in sediment 46 mya.Rodhocetus fossils in sediment 46 mya.

Where is the gap? Draw an Where is the gap? Draw an intermediate stage of animal.intermediate stage of animal.

AdaptationsAdaptations

Variations that help an organism Variations that help an organism survive and reproducesurvive and reproduce

How does evolution occur?How does evolution occur?

Theory of Natural SelectionTheory of Natural Selection

Variations in species provide an advantage for Variations in species provide an advantage for survival = adaptationssurvival = adaptations

Organisms with these variations are better Organisms with these variations are better adapted to their environment adapted to their environment

These organisms get more food and reproduce These organisms get more food and reproduce more passing their traits on to their offspringmore passing their traits on to their offspring

Over time a population changes based on Over time a population changes based on these adaptations, eventually creating a new these adaptations, eventually creating a new speciesspecies