Transcript Fossil Evidence of Evolution

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:
1. 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
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.