Fossil and Extinction What are the Different Types of Fossils and How Do They Show Evidence of Evolution and Extinction?

The Fossil Record On your way to school you might have seen an oak tree or heard a robin. These organisms shed leaves or feathers, their characteristics remain the same from day to day . If you were to travel a few million years back in time, you would not see oak trees or robins. You would see different species of trees and birds, This is because species change over time.

Fossils Fossils - are the remains or evidence of a once-living organism . Fossil record - made up of all the fossils ever discovered on Earth. The fossil record provides evidence that species have changed over time. It contains millions of fossils that represent may thousands of species. Most of these species are no longer alive on Earth .

Fossil Example Scientists think that this is what the giant bird Titanus might have looked when it was alive . The picture is based on fossils that have been discovered.

Fossil Formation Two main ways that fossils form: Mineralization- After an organism dies, its body could be buried under mud, sand, or other sediments in a stream or river. When minerals in the water replace the organism’s original material and harden into rock, a fossil forms.

Fossil Formation 2. Carbonization – A fossil forms when a dead organism is compressed over time, and pressure drives off the organism's liquids and gases. Fish, insects, and plant leaves are preserved as carbon film.

Other Types of Fossil Formation Sometimes when an organism dies, its shell or bone might make an impression in mud or sand, When the sediment hardens so does the impression. Mold – the impression of an organism in a rock

Other Types of Fossil Formation A cast is a fossil copy of an organism in a rock. Sediments can later fill the mold and harden to form a cast. A single organism can form both a mold and a cast Molds and casts show only external features of organisms.

Trace Fossils Trace fossil - the preserved evidence of the activity of an organism Evidence of an organism’s movement or behavior – not just its physical structure, can also can be preserved in rock . Examples: Organism might walk across mud. Tracks

Original Material Fossils Original material fossils - Original tissues of an organism are preserved . Examples: Mammoths frozen in ice Saber –tooth cats preserved in tar pits

Determining a Fossil’s Age Scientists date the rocks the fossils embedded inside. Relative –Age Dating – A rock is either older or younger than rocks nearby. Scientists determine the relative order in which rock layers were deposited. Bottom layers are oldest and the top are youngest Determine the relative order in which species have appeared on Earth over time.

Absolute- Age Dating More precise Radioactive decay, a natural clocklike process in rocks, to learn a rock’s absolute age, or its age in years Measure the ratio or unstable isotopes to stable isotopes to find the age of a rock.

Geologic Time Scale A chart that divides Earth’s history into different time units. The longest time units in the geological time scale are eons. Earth’s history in divided into four eons. Phanerozonic- Earth’s most recent eons. Its subdivided into three eras.

Extinctions Extinction – occurs when the last individual organism of a species dies. Sudden disappearances of fossils in rock layers are evidence of extinction events. Evidence from the fossil record suggest extinction have been common throughout Earth’s history .

Environmental Changes What causes extinction? USUALLY ENVIRONMENTAL CHANGE Organisms depend on resources in the environment. Sometimes environments change. What happens to an individual organism? After a change happens, individual organisms of a species might not be able to find the resources they need to survive.

Sudden Changes Extinctions can occur when environments change quickly. ( High rate of extinction) For example: Volcanic eruption Meteorite impact This can affect global climate and food webs. Scientists hypothesize that the impact of a huge meteorite 65 million years ago contributed to the extinction of the dinosaurs.

Gradual Changes Not all environmental change is sudden. Earth’s tectonic plates move between 1 and 15 cm each year. Mountains form and oceans develop Isolates a species, the species might become extinct. Sea level changes.

Extinctions and Evolution Fossil record contains evidence of extinction and the appearance of many new species.

Extinction and Evolution The series of horse fossils suggests that the modern horses is related to other extinct species. These species changed over time in what appeared to be a sequence.

Extinct Animals http://www.50birds.com/extan/gextanimals1.htm http://www.worldwildlife.org/species/

Biological Evolution Change over time is evolution Biological evolution - The change over time in populations of related organisms . Charles Darwin developed a theory about how species evolve from other species.