A Brief History of Life on Earth
Geology Today
Chapter 15
Barbara W. Murck and Brian J. Skinner
Horned dinosaurs, 70 m.y. ago
N. Lindsley-Griffin, 1999
Mark Marcuson; Nebraska State Museum
Organization of Life
Amino acids are the basic building blocks of proteins.
Biosynthesis is the linking together (or polymerization) of
small organic molecules (like amino acids) to form larger
ones, called biopolymers (like proteins).
N. Lindsley-Griffin, 1999
Organization of Life
DNA - Deoxyribonucleic acid - is a
double-chain biopolymer that
consists of two twisted chain-like
molecules held together by organic
molecules.
DNA contains all the genetic
information needed for organisms
to grow and reproduce.
DNA stores genetic information.
Fig. 15.7, p. 443
N. Lindsley-Griffin, 1999
Organization of Life
RNA - Ribonucleic acid - is a singlestrand molecule similar to one-half
of a DNA strand.
RNA contains the information
needed to construct an exact
duplicate of the protein molecule.
RNA transmits the genetic
information that DNA stores.
Fig. 15.7, p. 443
N. Lindsley-Griffin, 1999
Organization of Life
Metabolism is the set of
biochemical reactions by
which organisms produce
and extract food energy.
Short chain of fossil cyanobacteria cells,
1.0 b.y. Bitter Springs Chert, N. Australia
Fermentation is anaerobic
metabolism - without
oxygen.
Respiration is aerobic
metabolism - with oxygen.
Living cyanobacterium Oscillatoria
N. Lindsley-Griffin, 1999
Oxygen in
Atmosphere
Photosynthesis - process
whereby plants use light
energy to cause carbon
dioxide to react with water.
Byproducts are:
Organic substances carbohydrates
and free oxygen
All free oxygen now in the
atmosphere originated by
photosynthesis.
Fig. 15.3, p. 439
N. Lindsley-Griffin, 1999
Early Earth
Major events and trends
in Earth’s surface
environment during the
first 4.0 b.y.:
Ocean forms, 4.4 b.y.
Oldest bacteria, 3.8 b.y.
Blue-green algae, 3.0 b.y.
Iron formations, 2.2 b.y.
Oxygen buildup, 2.0 b.y.
Eukaryotes, 2.0 b.y.
Abundant multicelled
fossils, 0.6 b.y.
Fig. 15.1, p. 437
N. Lindsley-Griffin, 1999
Early Earth
4.6 b.y.
The solar system coalesced 4.6 b.y. ago
from a cloud of cosmic dust and gas.
Gravitational compaction caused nuclear
fusion to begin in the sun.
Planetesimals gathered into larger
clusters to make planets; leftover
material formed asteroids and comets.
Asteroid Ida
N. Lindsley-Griffin, 1999
Nebula M16
Early Earth
4.5 b.y.
Probably molten at
first, Earth was
battered by repeated
impacts of
planetesimals.
The first atmosphere
was stripped away by
solar wind or impacts,
but was replenished by
volcanic eruptions.
It was too hot for water
to exist on the surface.
John Drummond; Time-Life Books
N. Lindsley-Griffin, 1999
Early Earth
4.4 b.y.
As Earth cooled, water vapor in the atmosphere condensed
and rained out to form oceans - maybe as early as 4.4 b.y. ago.
Don Davis; Time-Life Books
N. Lindsley-Griffin, 1999
Early Life
3.8 b.y.
Near the end of the intense bombardment period, about 3.8
b.y. ago, Earth still was wracked by meteorite impacts and
volcanic eruptions. It was a tough place to make a living.
Don Davis; Time-Life Books
N. Lindsley-Griffin, 1999
Origin of Life
The first life required
chemosynthesis of
organic compounds such as amino acids from inorganic
materials like
atmospheric gases,
to make proteins.
Lightening bolts discharge through volcanic
gases, Mt. Pinatubo, Philippines
Fig. 15.4, p. 441
N. Lindsley-Griffin, 1999
Origin of Life
One hypothesis
suggests simple
microbes first formed
in aerosols - tiny liquid
droplets or solid
particles suspended in
the atmosphere.
Could lightening
discharges have
provided the energy?
Lightening bolts discharge through volcanic
gases, Mt. Pinatubo, Philippines
Fig. 15.4, p. 441
N. Lindsley-Griffin, 1999
Origin of Life
Black smoker
Galapagos Is.
Fig. 15.6, p. 443
Because of the adverse surface conditions, the most likely place
for life to develop might have been at deep ocean thermal
springs, protected from meteorite bombardment.
Both the raw materials and the heat needed for chemosynthesis would have
been available here.
N. Lindsley-Griffin, 1999
Origin of Life
3.5 b.y. +?
The first life was
microbial.
Oldest fossils of microbes
found on Earth (so far) are
nearly 3.5 b.y. old.
Short chain of fossil cyanobacteria cells,
1.0 b.y. Bitter Springs Chert, N. Australia
Rocks in Greenland
thought to have formed as
byproducts of microbial
activity are 3.8 b.y.
Living cyanobacterium Oscillatoria
N. Lindsley-Griffin, 1999
Mars Life?
4.5-3.6 b.y.
Meteorite ALH84001 was
found in Antarctica in 1984.
It is 4.5 b.y. old.
Its chemistry is unlike Earth rocks - instead, it is like Mars
rocks analyzed by remote landers.
It is thought to have originated on Mars, but was “splashed”
into space by an impact near the end of the heavy
bombardment period. It remained in space until about 16,000
years ago, when it was attracted by Earth’s mass and fell onto
Antarctica.
Fig. 15.5, p. 442
N. Lindsley-Griffin, 1999
Mars Life?
4.5-3.6 b.y.
In 1996, tiny tube-like
structures were discovered
inside the meteorite.
Some scientists have
interpreted these structures
as fossils of microbes - if so,
they would be at least 3.6
b.y. old.
The debate is raging hotly stay tuned for further
developments.
N. Lindsley-Griffin, 1999
Fig. 15.5, p. 442
Oxygen
Atmosphere
1.8 b.y.
Chemical sediments from 2.0 to 1.8 b.y.
consist of oxygen-poor iron minerals
plus oxygen-rich iron minerals
Interlayering reflects a transition from oxygen-poor
atmosphere to oxygen-rich atmosphere during this time.
Brockman Formation, 2.0 b.y., W. Australia (Fig. 8.10, p. 227)
N. Lindsley-Griffin, 1999
All organisms are composed of cells, a
Early Life
complex grouping of chemical compounds
enclosed in a membrane, or porous wall.
Prokaryotic cells store their DNA in a poorly defined part
of the cell, not separated from the cytoplasm - the main
body of the cell - by a membrane.
Prokaryotic cell
lacks a welldefined nucleus
Fig. 15.8, p. 445
N. Lindsley-Griffin, 1999
Early Life
Eukaryotic cells include a distinct nucleus surrounded by a
membrane, as well as other membrane-bounded organelles
- well defined parts that each have a specific function.
Eukaryotic cell has
a well-defined,
membrane-bound
nucleus
Fig. 15.8, p. 445
N. Lindsley-Griffin, 1999
Early Life
Prokaryotic cells are the earliest Eukaryotic cells are larger and
more complex; most require
and simplest cell forms; many
oxygen.
are anaerobic.
Modern bacteria are prokaryotes.
Fig. 15.8, p. 445
Most advanced life forms are
Eukaryotes.
N. Lindsley-Griffin, 1999
How Fossils Form
Mineralization - bones and
other hard parts are
replaced by minerals
carried in solution by
groundwater.
Petrified wood has been
replaced by mineralization.
Even though its original woody
texture is preserved, it consists
entirely of minerals like
crystalline quartz, chalcedony, or
agate.
Petrified Forest Natl. Park, Arizona
Fig. 15.16, p. 455
N. Lindsley-Griffin, 1999
How Fossils Form
Trace fossils are indirect
evidence of organisms:
tracks and trails
wormholes and burrows
nests
feces (coprolites)
calcite mounds (stromatolites)
Dinosaur tracks, 65 m.y.a.
Fig. 15.18, p. 455
N. Lindsley-Griffin, 1999
How Fossils Form
Some organisms are frozen in permafrost, like this wooly
mammoth.
Some organisms are trapped and preserved whole in amber or
tar, like this Eocene to Oligocene age mosquito.
(Fig. 15.15, p. 454).
N. Lindsley-Griffin, 1999
Evolution
Darwin’s Finches
Fig. 15.13
p. 451
Charles Darwin visited the Galapagos Islands in 1832.
He observed many species of finches on the islands, whereas only
one lives on the nearby continent of South America.
Each finch species occupies a different environment, and eats
different food. Their beaks and their feeding behavior vary to
exploit the sparse resources as effectively as possible.
N. Lindsley-Griffin, 1999
Evolution
Darwin’s Finches
Fig. 15.13
p. 451
To explain his observations, Darwin hypothesized that species
can adapt to new conditions through natural selection.
Individuals who are well-adapted are more likely to pass on
their characteristics to the next generation.
Individuals who are poorly adapted tend to be eliminated and
are less likely to produce offspring to perpetuate their genes.
N. Lindsley-Griffin, 1999
Evolution
Darwin’s Finches
Fig. 15.13
p. 451
All natural populations have individuals with different
characteristics. In any setting, some features work better than
others, and these individuals will tend to reproduce more
successfully.
Over time, the entire population will evolve towards a better
adaptation.
N. Lindsley-Griffin, 1999
Evolution
Darwin’s Finches
Fig. 15.13
p. 451
Back to Darwin’s Finches -A study of DNA released in mid-1999 showed that all the
Galapagos finches are closely related to each other.
They probably were derived from the South American finch
that Darwin hypothesized was their common ancestor.
N. Lindsley-Griffin, 1999
Evolution
The iguana problem:
Galapagos Islands are only 3
m.y. old.
DNA from Galapagos iguanas
shows that they have evolved
about 7 m.y. since splitting off
from their South American
cousins.
BUT -- The islands did not even
exist when the iguanas left
South America 7 m.y. ago.
Galapagos Iguana
Fig. B15.1, p. 452
N. Lindsley-Griffin, 1999
Evolution
The iguana problem (Cont.):
The Galapagos Islands are a
hot spot chain like Hawaii, in
which the older volcanoes have
subsided below sea level.
Hypothesis: the ancestral
iguanas swam from South
America to the easternmost
island. As time passed and each
island in the chain subsided,
they moved west to the next
one. It took them 7 m.y. to
make the trip.
N. Lindsley-Griffin, 1999
Galapagos Iguana
Fig. B15.1, p. 452
Fossil Record - Archean
3.5 b.y.: The oldest known fossils are
chains of prokaryotic cells from a
chert in W. Australia.
Notice how similar they are to the possible
microbes in Mars meteorite ALH84001
N. Lindsley-Griffin, 1999
Fossil Record Precambrian
Stromatolites are layers of
calcium carbonate that
form in warm, shallow seas
by the activities of
photosynthetic bacteria.
Fossil stromatolites > 1.5
b.y. are evidence of
microbial activity during
the Proterozoic and
Archean (as far back as 3.0
b.y. or earlier).
N. Lindsley-Griffin, 1999
Stromatolites, Shark’s Bay, W. Australia (Fig. 15.10, p. 447)
Fossil Record Proterozoic
About 1.4 b.y.a. - oldest eukaryotes
By 1.0 b.y.a. - eukaryotes common
600 m.y. - Ediacara fauna: oldest
fossils of larger, multicellular, softbodied marine animals.
Named for Ediacara Hills, Australia.
Dickinsonia
costata worm-like, 7.5
cm across
Fig. 15.11
Mawsonia spriggi - a floating,
disc-shaped animal like a
jellyfish, 13 cm across.
p. 448
N. Lindsley-Griffin, 1999
Fossil Record - Late Proterozoic
Ediacaran Fauna are still poorly understood.
Some are simple blobs, others are like jellyfish, worms, or softbodied relatives of the arthropods.
They appear worldwide in strata about 600 m.y. old, suggesting a
relatively sudden explosion of soft multicelled forms.
N. Lindsley-Griffin, 1999
Fossil Record - Late Proterozoic
Plants: Land plants probably evolved from green algae about 600
m.y. ago. Life on land may have looked like this.
In the seas, bacteria and green algae were common at the end of
the Precambrian.
Green algae
(Fig. 15.22, p. 458)
N. Lindsley-Griffin, 1999
Fossil Record Cambrian
545-505 m.y.a. - beginning of
period of great diversification:
Higher atmospheric oxygen
affected skeletal biochemistry
and supported larger organisms.
Trilobite, Utah (Fig. 15.20)
Ozone developed to level where
it blocked ultraviolet radiation.
Eukaryotes invented sexual
reproduction.
Hard parts appeared.
N. Lindsley-Griffin, 1999
Soft-bodied arthropod, B.C.
(Fig. 15.21, p. 457)
Fossil Record Cambrian
545-505 m.y.a.:
Hard external skeletons
protected trilobites, clams,
snails, and sea urchins from
predators.
Trilobite, Utah (Fig. 15.20)
Soft-bodied animals diversified
from Ediacaran fauna into the
Burgess Shale fauna.
Gills, filters, efficient guts, circulatory
systems, and other features of more
advanced life forms developed.
Soft-bodied arthropod, B.C.
N. Lindsley-Griffin, 1999
(Fig. 15.21, p. 457)
Fossil Record - Cambrian
545-505 m.y.a.: reconstruction of Burgess Shale fauna
N. Lindsley-Griffin, 1999
J. Wiley & Sons, The Blue Planet
Fossil Record - Ordovician
490-443 m.y.a.: Seas held abundant marine invertebrates with
sophisticated adaptations to different conditions.
Straight-shelled cephalopods, trilobites, snails,
brachiopods, and corals in a shallow inland sea.
N. Lindsley-Griffin, 1999
The Field Museum, Chicago
Fossil Record - Silurian
438-408 m.y.a.: This was the “Golden Age” of cephalopods and
brachiopods (a clam-like shellfish).
The first land plants developed, and the first arthropods
(scorpion-like invertebrates) ventured onto land.
N. Lindsley-Griffin, 1999
The Milwaukee Museum
Fossil Record - Devonian
408-360 m.y.a.: The
“Golden Age” of fishes
Lutgens and Tarbuck, 1999
N. Lindsley-Griffin, 1999
American Museum of Natural History, New York
Fossil Record - Devonian
408-360 m.y.a.: Land plants
became common. Vascular
plants developed - club
mosses and ferns.
These plants had structural
support from stems and
limbs and a vascular
system providing an
internal plumbing system
for water.
Modern fern leaf with dark
spores on underside
Fossil fern in shale, 350 m.y. (Fig. 15.23, p. 459)
N. Lindsley-Griffin, 1999
Fossil Record - Late Devonian
380-360 m.y.a. - First seed plants - the naked-seed plants developed. Gymnosperms like Glossopteris developed.
Ginkgos are long-lived relics of the ancient family of nakedseed plants, so are conifers.
N. Lindsley-Griffin, 1999
Modern and fossil ginkgo leaves (Fig. 15.24, p. 459)
Fossil Record - Carboniferous
360-286 m.y.a.: Age of amphibians; first winged reptiles and
first winged insects. Widespread forests and swamps.
Ichthyostega had features like a tail that it inherited from fish; and legs that
allowed it to move around on land.
N. Lindsley-Griffin, 1999
Fig. 3.9, p. 65
Michael Rothman; John Wiley & Sons
Fossil Record Pennsylvanian
N. Lindsley-Griffin, 1999
320-290 m.y.a.: peat swamps common,
with scale trees, seed ferns, scouring
rushes, and large dragonflies
The Field Museum, Chicago
Fossil Record - Permian
286-248 m.y.a.: Amphibians decline; reptiles and insects
increase; first mammal-like reptiles appear. Nonseed plants
decline.
Eryops, a carnivorous amphibian -The Field Museum, Chicago
N. Lindsley-Griffin, 1999
Fossil Record - Triassic
225 m.y.a.: First dinosaurs and mammals; explosive radiation
of dinosaurs.
(Primitive Ornithischia, an early dinosaur)
N. Lindsley-Griffin, 1999
National Museum of Natural Sciences, Canada
Fossil Record - Jurassic
213-144 m.y.a.: The Age
of dinosaurs; forests of
gymnosperms and ferns
cover most of Earth
J.R. Griffin, 1999
Smithsonian Natural History Museum
Fossil Record - Jurassic
213-144 m.y.a.: Age of dinosaurs
American Museum of Natural History, New York, N.Y.
N. Lindsley-Griffin, 1999
Fossil Record - Jurassic and Cretaceous
213-65 m.y.a.: Age of dinosaurs. Birds appear.
Dragonfly, Brazil
7 cm (3 in.) long
Fig. 15.26, p. 460
N. Lindsley-Griffin, 1999
Fig. 3.9, p. 65
Breck Kent; John Wiley & Sons
Fossil Record Jurassic -Cretaceous
175-65 m.y.a. :
This nesting mother, a birdlike
dinosaur called Oviraptor, was found
curled protectively around a nest
containing at least 20 eggs - evidence
that dinosaurs cared for their young.
Archaeopteryx: an early bird, has
skeleton and teeth very similar to
those of dinosaurs as well as
detailed impressions of feathers.
Fig. 15.27, p. 462
N. Lindsley-Griffin, 1999
Fossil Record - Cretaceous
144-65 m.y.a.: Plesiosaurs infested the beaches
N. Lindsley-Griffin, 1999
Smithsonian Natural History Museum
Fossil Record - Cretaceous and Tertiary
144-65 m.y.a. - first flowering plants appear.
After the K-T boundary, flowering plants diversify and spread
explosively over the planet, as do mammals.
N. Lindsley-Griffin, 1999
Fossil sweet gum, 1.5 m.y., Idaho - next to modern sweet gum fruit
(Fig. 15.25, p. 459)
Fossil Record - K-T Boundary
65.0 m.y.a.:
Cretaceous -Tertiary
Boundary
Many species and genera,
including the dinosaurs,
died out at end of
Cretaceous
One hypothesis: Earth was
hit by a meteorite - at
Chixulub, in the Yucatan
area of Mexico
Planetary Society, J.R. Griffin, 1999
Fossil Record - Tertiary: Paleocene
65-54.9 m.y.a.: Beginning of modern life forms following the
K-T Boundary extinctions.
Age of mammals began, grasslands spread.
U.S. Geological Survey
N. Lindsley-Griffin, 1999
Fossil Record - Tertiary: Eocene
N. Lindsley-Griffin, 1999
54.8-38 m.y.a.
American Museum of Natural History, New York
Fossil Record - Tertiary: Oligocene
38.0-24.6 m.y.a.: horses, antelopes, cats, oreodonts
American Museum of Natural History, New York
N. Lindsley-Griffin, 1999
Fossil Record - Tertiary: Miocene
24.6-5.1 m.y.a.: horses, antelopes, and other mammals.
N. Lindsley-Griffin, 1999
Fig. 3.9, p. 65
Breck Kent; John Wiley & Sons
Fossil Record - Tertiary: Miocene
24.6-5.1 m.y.a.: horses, rhinoceri, and elephants.
N. Lindsley-Griffin, 1999
American Museum of Natural
History, New York
Fossil Record - Quaternary: Pleistocene
2.0-0.1 m.y.a.:
deer family
and elephant
family
N. Lindsley-Griffin, 1999
American Museum of Natural History, New York
Fossil Record - Quaternary: Pleistocene
2.0-0.01 m.y.a.: horses, cats, elephants, bison, dire wolves
American Museum of Natural History, New York
N. Lindsley-Griffin, 1999
Fossil Record - Quaternary: Pleistocene
2.0-0.01 m.y.a.: mammals successfully colonized all
environments
J.R. Griffin, 1999
Larson, Illinois State Museum
Fossil Record - Quaternary: Pleistocene
2.0-0.01 m.y.a.:
subglacial
areas,
La Brea tar
pits, S. CA
N. Lindsley-Griffin, 1999
American Museum of Natural History, New York
Fossil Record - Quaternary: Pleistocene
< 0.1 m.y.a.: Western Nebraska when first humans were appearing
N. Lindsley-Griffin, 1999
Mark Marcuson, Nebraska State Museum
Fossil Record - Quaternary
4.4-0 m.y.a.: Hominids diverged from an early ape-like family.
(Poor fossil record and missing transitional forms complicate the story and
leave many gaps, but new fossils are being found each year.)
Ardipithecus ramidus - 4.4 (bipedal, erect forest dweller)
Ardipithecus anamensis - 4.2-3.9 (bipedal, apelike skull)
Australopithecus afarensis (“Lucy”) - 3.9-2.8 (bipedal, apelike face with
sloping forehead, human-like bodies. Lived together in family groups.)
and other species of Australopithecus - 3.0-1.1
Homo habilis - 2.2-1.6 m.y.a. (used stone tools, so
may be related to Homo sapiens, but skull is like
australopithecines)
Homo habilis
N. Lindsley-Griffin, 1999
www.onelife.com
Fossil Record - Quaternary
Hominids (Cont.)
Homo erectus - 1.8-0.4 m.y. (Peking man,
Java man: developed large brains, tools,
weapons, fire, and learned to cook food.)
Homo sapiens archaic - 500-200 t.y.a.
(Skulls intermediate between Homo erectus
and Homo sapiens sapiens)
Homo sapiens neandertalensis -200-30 t.y.a
(teeth and brain similar to ours,
but DNA different, burial sites suggest
they practiced some form of religion.)
N. Lindsley-Griffin, 1999
Neandertal
www.onelife.com
Fossil Record Quaternary: Holocene
Homo sapiens sapiens 120,000-present
N. Lindsley-Griffin, 1999