2.  Earth is estimated to be about 4.6 billion
years old.
 Atmosphere was very harsh.
 Very hot.
 Lot’s of water vapor in the atmosphere.
 Volcanic activity.
 NO BREATHABLE OXYGEN GAS!
 Carbon dioxide, ammonia, hydrogen gas,
were present
 We needed to find earliest evidence of
life for clues to what it was

3. Origin of Life
 Scientists had hard time
finding ancient evidence of
life
 45 years ago we found out
why.
 Most ancient life was
Cyanobacteria fossil about
microscopic=microfossils 1,000,000,000 (1 billion)
years old found in stromatolites
 Oldest microfossil3.5
billion years old
 1st organisms were bacteria

4. How did life begin?
 Extraterrestrial origin
 Creation ( ID )—”divine forces”
 From non-living matter “Chemical Evolution”
 Main proposal as to how this happened
Organic compounds (microspheres)
Assemble to create 1st bacterial cell
Some bacterial cells became organelles of
others to form eukaryotic cells
Eukaryotic cells join to form multicellular
organisms

5. Origin of Life’s Chemicals
 Miller-Urey
 Experiment that
recreated atmosphere
of early Earth
 Hypothesis: Can
organic compounds
form in early Earth
conditions?
 Results: amino acids,
nucleotides, lipids,
carbohydrate pieces
out

6. Self Assembly
 Molecules can
spontaneously form into
droplets—oil and water
 Protein + water =
“microspheres”
 Solution with lipids will self
assemble into a lipid bilayer
 Droplets can enclose watery
solution different from
surroundings
 BOTH SMALL SPHERES
RESEMBLE CELL
MEMBRANES!

7. 1 genetic material- RNA
st
 Earth’s early surface was inhospitable
due to immense UV radiation
 Deep sea vents on the sea floor may
have provided sheltered location for
life.
 RNA can form in labs under conditions
similar to areas near deep sea vents
 Oldest living prokaryotes found there
today…

8. Road to Modern Organisms
 1st
life was bacteria unicellular prokaryotes
 Photosynthesis changed Earth’s
atmosphere released O2 - cyanobacteria!!!!
 2nd was unicellular eukaryotes
Endosymbiotic Theory
 Then multicellular organisms

9. GENERAL EVOLUTION TIMELINE
 EARTH
 MOLECULES
 PROKARYOTES
 SINGLE-CELLED EUKARYOTES
 MULTICELLULAR ORGANISMS
 MARINE INVERTEBRATES
 MARINE VERTEBRATES
 LAND PLANTS
 LAND VERTEBRATES
 REPTILES
 GYMNOSPERMS--EVERGREENS
 MAMMALS
 DINOSAURS
 BIRDS
 ANGIOSPERMS-- FLOWERING PLANTS
 DINOSAUR EXTINCTION
 EARLY PRIMATES
 ANTHROPOIDS
 HUMANS

10.  Timeline of Life
 Earth formation
• 4500 million (4.5 billion) years ago
 Miller’s molecules
• 4000 million (4.0 billion) years ago
• amino acids
• proteins
• carbohydrates
• nucleic acids
• mass extinction

11.  First life on Earth
• 3500 million years ago
• bacterial (prokaryotic) cell
 Evolution of cyanobacteria
• Blue-green bacteria
• Photosynthesis
• Oxygen production!
 First single eukaryotic cells
• 2200 million years ago
• Organelles such as mitochondria and chloroplasts
made of prokaryotic cells. Have their own DNA

12.  First multicellular organisms
• 2000 million years ago
• eukaryotic algae
• OXYGEN IN ATMOSPHERE to form protective
ozone layer

O3

absorbs UV light

protects DNA from mutation

allowed life on land
 First invertebrate marine animals
• 500 million years ago
• Jellyfish

13.  First marine vertebrates and land plants
• 450 million years ago
• Jawless fish
• Giant ferns
 First land vertebrates
• 340 million years ago
• amphibians—toads frogs
• lungs  blood flow from heart to lungs
• lose water from their skin so must stay moist
 First reptiles and insects
• 300 million years ago
• snakes, crocodiles, turtles, lizards
• skin watertight, so could live out of water
• spiders

14.  First gymnosperms
• 290 million years ago
• naked seeds
• Evergreen trees
 First mammal like reptiles
• 240 million years ago
• 4 chambered heart
• milk
• fur

15.  First dinosaurs
• 220 million years ago
• Dinosaurs dominated in the Jurassic period
 First birds evolve
• 180 million years ago
• reptiles found on land, sea and in air
• Archeopteryx
 Flowering plants appear
• 120 million years ago
• angiosperms
 Dinosaur extinction
• 65 million years ago

16.  Very early primates
• 64 million years ago
• Order of mammals that apes, monkeys, and
humans belong to.
 Anthropoids evolve
• 35 million years ago
• Day active-primates
• Animals with five flexible fingers
• Monkeys, apes, and humans

17.  Lucy fossil
• 4 million years ago
• earliest hominid—common ancestor to humans
and apes (gorillas, orangutans, and chimps)
• walked upright, small skull, teeth intermediate
between humans and apes
 Homo sapiens
• 0.1 million years ago (100,000 years ago)
• Human species
• Direct ancestor is Homo erectus