• Speciation – process by which new
species arrive.
• Macroevolution – evolution on a grand
scale
• Adaptive radiation - evolution of many
diversely adapted species from a common
ancestor
• Introduction to the History of Life
• The Origin of Life
• Organic (Chemical) Evolution
• Major Lineages of Life
• Conditions on early Earth
• Four Stage Hypothesis of Origin
• RNA, the first genetic material
• Natural selection’s role – directed
evolution
• Four Stage Hypothesis of Origin
1. Abiotic synthesis of building blocks
2. Production of organic polymers
3. Origin of self-replicating molecules
(making inheritance possible)
4. Protobionts are packaged with
material that makes internal
chemistry different from
surroundings
• Age of Earth is ~4.6 billion years
• Atmosphere had little free O2
• Included CO2, H2O, CO, H2, N2
• Maybe also NH3, H2S, CH4
• Lack of oxygen meant that the environment
would have “reducing” nature
• Requirements for chemical evolution to
produce life
• Absence of oxygen
•Energy
• Chemical building blocks
• Sufficient time
• 1920s – A.I. Oparin and J.B.S. Haldane
• 1953 – Stanley Miller and Harold Urey
test the Oparin-Haldane hypothesis
Miller-Urey
experiment
•Other hypotheses:
• “hot rocks” – organic molecules are
concentrated as water evaporates from
geothermal activity
• Clay – clay contains charged particles which
retains organics when runoff is collected
• Deep sea vents produce many inorganic
catalysts that could aid in the making of
polymers
•Self-replicating RNA molecules
•Function as both enzyme and substrate
for replication
• Ribozyme is enzymatic RNA
•First step in evolution of the
DNA / RNA / protein system
• Separate internal environment from external
surroundings by a biological membrane
• As protobionts became more similar to cells they
would have evolved the following:
• Binary fission
• Homeostasis
• Catalytic activity
Microspheres – a type of protobiont
• Microspheres
• Formed from water and polypeptides
• Electric gradient on surface
• Selective permeability
• Liposomes
•Lipids organized into a molecular bilayer
• Selective permeability
• Behave dynamically – grow, split, etc.
• Large pool of RNA molecules with
different sequences
• Selected for ability to catalyze a
reaction
• Amplify / mutate / repeat
Directed evolution
• In the RNA world, ribozymes catalyzed
protein synthesis
• DNA formed from double strands of RNA
• DNA more stable than RNA
• Heterotrophs that feed on organic
molecules
• Anaerobic fermentation process to obtain
energy
• Organic molecule food stock became scarce
• Photosynthetic production of organic
molecules
• Cyanobacteria evolved later and could split
water molecules which released oxygen
• More efficient energy production using
oxygen respiration
• Significant oxygen in the atmosphere-2 bya
• Ultraviolet radiation forms O3 from O2 in
the upper atmosphere
• Prevents UV from reaching Earth
• Enabled organisms to live in surface
waters and on land
Ozone
formation
• Endosymbiont theory
•Mitochondria and chloroplasts derived
from prokaryotes
•Ingested but not digested
•Reproduced along with host cell
Endosymbiont
theory
• Linnaeus’ two-kingdom system
• Plant (non-moving) and Animal (moving)
• Robert Whittaker’s five-kingdom system
• Plantae, Animalia, Fungi, Protista, Monera
• Carl Woese’s three-domain system
•Eukarya, Archaea, Bacteria
Era
Cenozoic
Mesozoic
Paleozoic
Precambrian
Time
Period
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Time
(millions of
years ago)
1.8–present
65–1.8
145–65
208–145
245–208
290–245
363–290
410–363
440–410
505–440
544–505
650–544
Key Events
Glaciations; mammals increased; humans
Mammals diversified; grasses
Aquatic reptiles diversified; flowering plants; mass extinction
Dinosaurs diversified; birds
Dinosaurs; small mammals; cone-bearing plants
Reptiles diversified; seed plants; mass extinction
Reptiles; winged insects diversified; coal swamps
Fishes diversified; land vertebrates (primitive amphibians)
Land plants; land animals (arthropods)
Aquatic arthropods; mollusks; vertebrates (jawless fishes)
Marine invertebrates diversified; most animal phyla evolved
Anaerobic, then photosynthetic prokaryotes; eukaryotes,
then multicellular life