CHAPTER 14 NOTES

1
CHAPTER 14 NOTES
HOW LIFE BEGAN?
2
Inorganic (nonliving) matter was transformed into
simple organic molecules

• Miller-Urey experiment (they modeled the ancient
  atmosphere in a reacting chamber, then electrodes
  produced sparks to simulate lightning and after
  one week they found the liquid produced by the
  experiment contained amino acids the building
  blocks of proteins)
• Eventually these simple organic molecules changed
  into cells with DNA and a nucleus

3
(No Transcript)
4
FOSSILS

• Paleontologists are scientists who study fossils
• The fossil record provides evidence about the
  history of life on Earth and it also shows how
  different groups of organisms, including species,
  have changed over time
• Most fossils form in sedimentary rock

5
FOSSIL DATING

• RELATIVE VS. RADIOACTIVE

6
RELATIVE DATING

• Determines the age of a fossil by comparing its
  placement with that of fossils in other layers of
  rock
• Oldest fossils are in lower layers of the rock
• Draw the picture on your notes which fossil is
  older? _____

B
7
RADIOACTIVE DATING

• The use of half-lives to determine the age of a
  fossil
• Radioactive decay occurs at a constant rate
  called a HALF-LIFE (the time it takes for half of
  the atoms in a sample to undergo radioactive
  decay)
• EX. The half-life of Potassium-40 is 1.26
  billion years
• Ex. The half-life of Carbon-14 is 5730 years
• Potassium dating is used for rocks that are
  suspected to be billions of years old and carbon
  dating is used for younger fossils (50,000 years)

8
(No Transcript)
9
EXAMPLE PROBLEM

• Suppose there are 16 grams of Carbon-14 in a
  living snail shell and 4 grams of Carbon-14 in a
  fossilized snail shell
• How many half-lives has this fossil gone through?
• 2
• What is the age of the fossil if each half-life
  of Carbon-14 takes 5730 years?
• 5730 X 2 11,460
• How many grams of Carbon-14 will be left if the
  snail shell goes through one more half-life?
• 2 grams

10
GEOLOGIC TIME SCALE

• In order to catalog the 4 billion years of life
  on Earth, scientists have created the geologic
  time scale to represent evolutionary time
• The scale is divided into large time spans called
  ERAS, which is subdivided into PERIODS

11
MOST RECENT
GEOLOGIC TIME SCALE
BEGIN
END
OLDEST
12
(No Transcript)
13
MASS EXTINCTION

• When majorities of species were eliminated during
  a time period very quickly
• Ex. Dinosaurs during the Cretaceous mass
  extinction
• These mass extinctions can have various causes
  volcanoes, change in atmosphere, lands shifting,
  large comet or asteroid, weather changes