Earth Science 3.4 : Looking at Fossils

Earth Science 3.4,[object Object],Looking at Fossils,[object Object]

Describe five ways that different types of fossils form.,[object Object],List three types of fossils that are not part of organisms.,[object Object],Explain how fossils can be used to determine the history of changes in environments and organisms.,[object Object],Explain how index fossils can be used to date rock layers.,[object Object],Objectives:,[object Object]

Fossilized Organisms,[object Object],Fossil,[object Object],The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock.,[object Object],Most often preserved in sedimentary rock, but other materials can also preserve evidence of past life.,[object Object],Fossils in Rocks,[object Object],When an organism dies, it either begins to decay or is consumed by other organisms. Sometimes dead organisms are quickly buried by sediment, which slows down decay.,[object Object],Shells and bones are more resistant to decay than soft tissues, so when sediments become rock, the harder structures are more commonly preserved.,[object Object]

Fossils in Amber,[object Object],Organisms occasionally become trapped in soft, sticky tree sap, which hardens and becomes amber.,[object Object],Insect fossils have often been preserved in this way, but frogs and lizards have also been found in amber.,[object Object],Petrifaction ,[object Object],Process in which minerals replace and organism’s tissues.,[object Object],Permineralization,[object Object],Process in which the pore space in an organism’s hard tissue is filled up with mineral.,[object Object],Replacement,[object Object],Process in which an organism’s tissues are completely replaced by minerals.,[object Object]

Fossils in Asphalt ,[object Object],There are places where asphalt wells up at the Earth’s surface. These thick, sticky pools can trap and preserve organisms.,[object Object],Frozen Fossils,[object Object],Since cold temperatures slow down decay, many types of fossils have been found preserved in ice.,[object Object]

Other Types of Fossils,[object Object],Trace Fossils,[object Object],Naturally preserved evidence of animal activity,[object Object],Examples:,[object Object],Preserved animal tracks,[object Object],Preserved burrows or shelters that were made by animals,[object Object],Coprolite, which is preserved animal dung.,[object Object],Molds and Casts are two more examples of fossils.,[object Object],Mold,[object Object],mark or cavity made in a sedimentary surface by a shell or other body.,[object Object],Cast,[object Object],type of fossil that forms when sediments fill the cavity left by a decomposed organism.,[object Object]

Using Fossils to Interpret the Past,[object Object],The Information in the Fossil Record,[object Object],Offers only a rough sketch of the history of life on Earth. ,[object Object],Incomplete because most organisms never became fossils.,[object Object],Scientists know more information about organisms that had hard body parts and that lived in environments that favored fossilization.,[object Object],History of Environmental Changes,[object Object],The fossil record reveals changes in an area’s climate over time.,[object Object],By using the fossils of plants and land animals, scientists can reconstruct past climates.,[object Object],History of Changing Organisms,[object Object],By studying the relationships between fossils, scientists can interpret how life has changed over time.,[object Object]

Using Fossils to Date Rocks,[object Object],Scientists have learned that particular types of fossils appear only in certain layers of rock.,[object Object],By dating the rock layers above and below these fossils,[object Object],Scientists can determine the time span in which the organisms that formed the fossils lived.,[object Object],If a type of organism existed for only a short period of time, its fossils would show up in a limited range of rock layers.,[object Object],These fossils are called index fossils.,[object Object],Index fossils,[object Object],Found in the rock layers of only one geologic age, and can be used to establish the age of the rock layers.,[object Object]

Earth Science 3.4 : Looking at Fossils

Ammonites,[object Object],Tropites,a marine mollusk similar to a modern squid, lived between 230 million and 208 million years ago.,[object Object],Trilobites,[object Object],Fossils of a genus of trilobites called Phacopsare another example of an index fossil.,[object Object],Trilobites are extinct and lived approximately 400 million years ago.,[object Object],When scientists find Phacops in a rock, they assume that the rock is approximately 400 million years old.,[object Object]

Earth Science 3.4 : Looking at Fossils

Earth Science 3.4 : Looking at Fossils

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados(20)

Destaque

Destaque(20)

Similar a Earth Science 3.4 : Looking at Fossils

Similar a Earth Science 3.4 : Looking at Fossils(20)

Mais de Chris Foltz

Mais de Chris Foltz(20)

Último

Último(20)

Earth Science 3.4 : Looking at Fossils