Today

1
Todays Agenda3/7

• 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!

2
What could have caused the two variations?

• Mutations
• Different allele combinations

3
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

4
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)

5
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.

6
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

7
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

8
Looking Into the Past

• Fossils Extinction
• Study Pack 5

9
Todays 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.

10
Fossils

• Fossils are traces of past organisms preserved in
  Earths 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

11
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 Fossils
• An organism leaves an imprint on sediment that
  later hardens to become rock

12
Types of Fossils

• Mineralized fossils
• Minerals replace wood or bone
• Petrified wood
• Frozen fossils

13
Determining a Fossils Age

• Relative Dating
• Younger rock layers are on top of older rock
  layers
• Provides an estimate of a fossils age
• Fossils found in lower layers of sedimentary rock
  are older than those found in upper layers
• Page 345

14
Determining a Fossils Age
15
Determining a Fossils Age

• Radiometric or absolute dating
• More accurate
• Use the amount of radioactive elements in the
  rock where the fossil is found to determine its
  age

16
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

17
The Fossil Record

• Fossils tell us
• What 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 Earths climate has changed over time
• How Earths surface has changed over time

18
Extinction

• Most of the organisms that have ever existed are
  extinct today
• Once a species is extinct, it can never come back
  to life

19
Extinction

• Natural causes competition, predation, climate
  changes, natural disaster
• Human activity habitat destruction, overhunting

20
Review

• In your own words, what is a fossil?
• In what kind of rock are fossils found?
• Why arent fossils found in igneous rocks?
• Why arent fossils found in metamorphic rocks?
• What are the different types of fossils?
• What parts of an organism are preserved as
  fossils?

21
Review

• Which provides a more exact age of a fossil
  relative or absolute dating?
• Which fossil is the oldest?
• Which fossil is the youngest?

2
3
22
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?

23
Review

• What causes extinction?
• What is probably the greatest cause of extinction
  today?