The History of Life
An Introduction to Biological Diversity
Early history of life
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Solar system~ 12 billion years
ago (bya)
Earth~ 4.5 bya
Life~ 3.5 to 4.0 bya
Prokaryotes~ 3.5 to 2.0 bya
stromatolites
Oxygen accumulation~ 2.7 bya
photosynthetic cyanobacteria
Eukaryotic life~ 2.1 bya
Multicelluar eukaryotes~ 1.2
bya
Animal diversity~ 543 mya
Land colonization~ 500 mya
The Origin of Life
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Spontaneous generation
vs. biogenesis (Pasteur)
The 4-stage Origin of life
Hypothesis:
– Abiotic synthesis of
organic monomers
– Polymer formation
– Origin of Self-replicating
molecules
– Molecule packaging
(“protobionts”)
Synthesis of Organic Compounds
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Oparin /Haldane hypothesis:
– Conditions of primitive earth
– “Primordial Soup”
– Volcanic vapors (reducing
atmosphere) + lightning +UV
radiation = complex molecule
formation (no O2)
Miller/Urey experiment:
– Tested Oparin hypothesis
– Heated “primordial soup”;
added sparks and condensed
– Produced some amino acids
and other organic compounds
– Some modern evidence
suggests that this would not
have been possible
Other Possible Sources of Life
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Synthesis of organic
compounds in deep
sea vents (sulfur,
iron, and no oxygen)
Organic compounds
arrived on meteorites
from space
Intelligent Design
???
Macromolecule Formation
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Amino acid polypeptides (proteinoids)
– formed from amino acid solutions dripped on hot
sand, clay or rock
Protobionts (coacervates)
– Abiotic macromolecules surrounded by a
membrane-like structure
– Could be the precursors to the first living cells
The “RNA World”
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First genetic material
was probably RNA
(Cech/Altman)
The first protobionts
contained selfreplicating ribozymes
Natural selection was
able to occur due to
base-pair mutations
Geologic History of Earth
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Fossil record led to
the creation of a
geologic record of
Earth’s history
3 Eons, further
divided into Eras and
Periods
– Eras marked by mass
extinctions of
organisms
Earth’s “History Clock”
The First Prokaryotes
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First fossils=
stromatolites
– Rocklike structures
composed of layers of
bacteria
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Electron Transport
Systems and ATP
production
Photosynthesis
– Produced great levels of
oxygen so that cellular
respiration, etc. could
occur
Eukaryotes by Endosymbiosis
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First eukaryotes
arose from the
symbiosis of small
prokaryotes inside
of larger ones
Multicellular Organisms
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Eukaryotes
organized into
colonies
Cells became
specialized so
that they could
not exist
independently
The “Cambrian Explosion”
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The sudden
appearance of most
major animal phyla
within the first 20
million years of the
Cambrian period
– Sponges and
cnidarians appeared
earlier
“Land, Ho!”
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Plants, fungi, and
animals gradually
colonized land
Developed
adaptations that
allowed them to
venture out of the
water
Continental Drift
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Earth’s crust is made
up of ever-moving
plates
All of Earth’s
landmasses were once
joined in “Pangaea”
The Evolution of Taxonomy
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2-kingdom system
(Aristotle, Linnaeus)
5-kingdom system
(Whittaker, 1969)
6-kingdom system
Three domain system