The History of Life on Earth

1
The History of Lifeon Earth
2
The Fossil Record

• Fossils are the preserved remains of organisms
  that lived long ago.
• Paleontologists study the fossil record to puzzle
  out the history of life on earth.

3

• Two different types of dating are used to
  determine the age of fossils
• Radioactive dating using radioactive
  isotopes to calculate the age of fossils
• Relative dating using rock layers to determine
  a fossils age (older fossils are in deeper rock
  layers)

4
RELATIVE DATING
5

• What Was the Earth Like Before Life?
• The Earth formed about 4.6 billion years ago
• Scientists use information from rocks, other
  planets, volcanoes to understand what the Earth
  was like before life

6

• The Earth Before Life Was
• Extremely hot extremely cold
• Stormy- Volcanoes, thunder lightening
• Lots of radiation- no ozone layer for protection
• Lots of gases in the atmosphere (air)
• BUT no breathable oxygen (no O2)

7

• The conditions were HORRIBLE if we went back in
  time we would not be able to surviveBUT somehow
  life was able to form on Earth
• How did life first come to be on Earth?
• Did it come on meteorites ???
• Was it alien magic ???
• Did God make it ???
• Spontaneous Generation???

8

• Most scientists believe life developed on Earth
  through MANY chemical reactions which made SIMPLE
  carbohydrates, lipids, proteins, nucleic
  acids....
• . Which chemical reactions then changed into
  COMPLEX carbohydrates, lipids, proteins, nucleic
  acids....
• Chemical reactions then somehow made them into
  SIMPLE cells

9

• Where did life first form on Earth?
• Scientists believe life first lived in the water
• The water first started to have many
  carbohydrates, lipids, proteins, nucleic acids in
  it and is referred to as primordial soup
• Eventually cells developed lived in the water.
  It took a long time for life to start living on
  land

10
Primordial Soup
11

• How can we test these ideas see if they are
  correct?
• Scientists have tried to recreate the Earth
  before life to see if they can get life to form
  from chemical reactions.
• In 1953 Miller Urey did an experiment to
  recreate the primitive Earth. They used
• Water gases from primitive Earth
• UV light - to simulate sunlight
• Electricity - to simulate lightening
• Boiled it - to simulate heat
• All was put in a glass apparatus to see if they
  could get life to form.

12
(No Transcript)
13

• After they let the experiment run for a while
  they found that simple carbs, amino acids,
  nucleotides were made by the chemical reactions.
• These substances were all building blocks of life
• So far scientists have only been able to make the
  building blocks of life in experiments, not
  actual living cells

14

• Whats missing?
• Another gas?
• More time?
• More energy?
• God? They dont know ???

15

• Some how
• Amino acids came together to form ? proteins
• Simple carbohydrates came together to form
  ?complex carbohydrates
• Nucleotides came together to form ? DNA RNA
• Scientists think RNA came first, then DNA
• Over time, the carbohydrates, lipids, proteins
  nucleic acids came together to form the first cell

16

• The first cells probably appeared about 3.8
  billion years ago
• The first cells were prokaryotic meaning
• No nucleus
• Very few organelles
• Simple primitive
• Can live in extreme areas -Ex volcanoes, hot
  springs

17

• Eventually some evolved into eukaryotic cells
  about 1.8 billion years ago.
• Eukaryotic cells
• have a nucleus
• Have many organelles
• Bigger more complex than prokaryotic cells
• Can live everywhere except extreme areas

18
Endosymbiotic Theory?

• Eukaryotic cells developed from a symbiotic
  relationship between several kinds of prokaryotes
  (bacteria) each had its own specialty and
  together formed a great unit

19
(No Transcript)
20

• It took billions of years for all the different
  organisms on the Earth to evolve. We think a
  basic map of how organisms evolved looks like
  this The tree of Life