FOSSILS

Fossils remains or imprints of an organism that lived long ago remains or imprints of an organism that lived long ago Formed 5 ways …. Formed 5 ways ….

1) In Rocks Dead organism is buried in sediment Dead organism is buried in sediment

2) Amber hardened tree sap hardened tree sap

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

4) Petrification Minerals replace tissues and become rock Minerals replace tissues and become rock

5) Asphalt/Tar La Brea Tar Pits in L.A. are at least 38,000 years old. These pools have trapped and preserved many different organisms, like the saber-toothed cats & dire wolves.

Types of Fossils

1) Trace Fossils Clues made by an organism, but do not include parts of the organism’s body Clues made by an organism, but do not include parts of the organism’s body

Other Examples of Trace Fossils Burrows (shelters made by animals that bury themselves in the sediment) may be filled with sediment and preserved. Burrows (shelters made by animals that bury themselves in the sediment) may be filled with sediment and preserved. “Caprolites” = dung (“poop”) that is fossilized. “Caprolites” = dung (“poop”) that is fossilized.

2) Molds Mold = the print/impression left in sediment/rock where organism was buried. Mold = the print/impression left in sediment/rock where organism was buried.

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

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What Can Fossils Tell Us? 1) The kind of organism 2) How the environment has changed (ex: forest fossils found in Antarctica show the climate was much warmer in the past) 3) How organisms have changed (evolved)

How Old Is It? To understand the history of the Earth, scientists have put fossils in order based on their ages. To understand the history of the Earth, scientists have put fossils in order based on their ages. They use relative dating and absolute dating methods They use relative dating and absolute dating methods

Index Fossils fossils are found only in rock layers of a certain age. fossils are found only in rock layers of a certain age. Ex: When scientists find Phacops in a rock layer, they know the rock layer is 400 million yrs old. Ex: When scientists find Phacops in a rock layer, they know the rock layer is 400 million yrs old.

Fossil Observation Fossil NameDrawingType / Age

Whale Evolution based on fossils Ocean adapted mammals Ocean adapted mammals Embryos of several whales have well- developed rear legs that disappear Embryos of several whales have well- developed rear legs that disappear Fossils of modern whales are not so “modern” Fossils of modern whales are not so “modern”

How did whales get here? Primitive whales (#1) found in rocks about 36 mya Primitive whales (#1) found in rocks about 36 mya

Place Mesonychid at 55 mya level Place Mesonychid at 55 mya level Pakicetus (#3) was found in sediment 50 million years old. Pakicetus (#3) was found in sediment 50 million years old. Basilasaurus (#4) fossils found – 37 mya Basilasaurus (#4) fossils found – 37 mya Rodhocetus fossils in sediment 46 mya. Rodhocetus fossils in sediment 46 mya. Where is the gap? Draw an intermediate stage of animal. Where is the gap? Draw an intermediate stage of animal.

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

How does evolution occur? Theory of Natural Selection Variations in species provide an advantage for survival = adaptations Variations in species provide an advantage for survival = adaptations Organisms with these variations are better adapted to their environment Organisms with these variations are better adapted to their environment These organisms get more food and reproduce more passing their traits on to their offspring These organisms get more food and reproduce more passing their traits on to their offspring Over time a population changes based on these adaptations, eventually creating a new species Over time a population changes based on these adaptations, eventually creating a new species