Types of Fossils

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Transcript Types of Fossils

Today’s Agenda…3/7
 Bellringer:
What causes variation among
organisms? What will happen to helpful
variations? What will happen to harmful
variations? (answer all questions)
 Notes on Fossils & Extinction
 Homework: Fossils and Extinction Questions
 Test corrections due by tomorrow!
What could have
caused the two variations?
 Mutations
 Different
allele combinations
What will happen when it reproduces?
Why?
 The
frog that survives will reproduce
 The offspring will have similar traits to the parents
 The frog will pass on the helpful trait
What will happen to each of the frogs?
Why?
 The
frog that blends in with the environment will
survive and reproduce
 The frog that did NOT blend in the environment
will not survive (it will be eaten by predators or
unable to hide from prey)
What will happen to the population of
frogs with each variation over time?
 The
population of the frog with the helpful
variation will increase.
 The population of the frog with the harmful
variation will decrease.
How does this activity show
natural selection?
 Nature
“selected” the frog with the camouflage to
survive and reproduce
 One frog was better suited to the environment than
the other, so it will survive
 The frog that is adapted to the environment will
survive
 One frog is a better fit for the environment so it
will survive
How does natural selection
lead to evolution?
 Evolution
is a gradual change in a species over
time.
 The species of frogs will change over time to
include mostly frogs that are well suited to that
environment.
 The other frog may evolve in an environment it is
better suited to
Looking Into the Past
Fossils & Extinction
Study Pack #5
Today’s Targets…
I
understand what fossils and the fossil
record are.
 I can describe the usefulness of the fossil
record.
 I understand that fossils provide evidence of
biological change.
Fossils
 Fossils
are traces of past organisms preserved in
Earth’s crust
 Can be actual structures or just imprints of
structures
 Fossils are normally found in sedimentary rock
 Layers
of sand, silt, clay or mud are compacted and
cemented together with fossils inside
Types of Fossils
 Page
344 Figure 9
 Cast fossils
 Minerals
fill in cracks to create a cast
 Example: Animal tracks become filled in
 Fossils

in amber
Sticky material from trees harden and trap insects
 Imprint
 An
Fossils
organism leaves an imprint on sediment that later
hardens to become rock
Types of Fossils
 Mineralized
fossils
 Minerals
replace wood or bone
 Petrified wood
 Frozen
fossils
Determining a Fossil’s Age
 Relative
Dating
 Younger
rock layers are on top of older rock layers
 Provides an estimate of a fossil’s age
 Fossils found in lower layers of sedimentary rock are
older than those found in upper layers
 Page 345
Determining a Fossil’s Age
Determining a Fossil’s Age
 Radiometric
 More
or absolute dating
accurate
 Use the amount of radioactive elements in the rock
where the fossil is found to determine its age
The Fossil Record
The fossil record provides us with clues that organisms
have changed over time
 Organisms have gone from simple to more complex
 It is incomplete
 Evidence of evolution

The Fossil Record
 Fossils
 What
tell us:
organisms in the past looked like & whether they
are similar to those today
 How organisms changed over time
 The roles the organisms played within communities and
food chains
 How Earth’s climate has changed over time
 How Earth’s surface has changed over time
Extinction
 Most
of the organisms that have ever existed are
extinct today
 Once a species is extinct, it can never come back
to life
Extinction
causes – competition, predation, climate
changes, natural disaster
 Human activity – habitat destruction, overhunting
 Natural
Review
 In
your own words, what is a fossil?
 In what kind of rock are fossils found?
 Why aren’t fossils found in igneous rocks?
 Why aren’t fossils found in metamorphic rocks?
 What are the different types of fossils?
 What parts of an organism are preserved as fossils?
Review
 Which
provides a more exact age of a fossil:
relative or absolute dating?
 Which fossil is the oldest?
 Which fossil is the youngest?
Review
 Does
the fossil record show all organisms that
lived in the past?
 Are most of the species of organisms in the fossil
record still alive today?
 According to the fossil record, how have
organisms changed over time?
 What clues does the fossil record provide?
Review
 What
causes extinction?
 What is probably the greatest cause of extinction
today?