Prehistoric Earth
Prehistoric Earth
Geologic Time
Giganotosaurus is the largest
carnivorous dinosaur discovered.
Time Scale
Earth’s history is divided into time units
based on:
• Major geological events
• Major life forms
• Mass extinctions
Eons- longest time subdivision based
on the abundance of certain types of fossils
Tulsa area fossils are from the
Pennsylvanian
Eras- 2nd longest time
subdivision based on
major worldwide changes
in types of fossils.
(Paleozoic, Mesozoic, &
Cenozoic)
Periods- 3rd longest time
subdivision based on
types of life that existed
worldwide.
Epochs- smallest time
subdivision characterized
by differences in regional
life.
Pre-Archean refers to the time before the
Archean. There is no evidence for life at
that time.
Archean means original or ancient. This
is a time when the first single-celled
organisms, like bacteria, began to
evolve.
Cenozoic
Era
Quaternary Period
Tertiary Period
Phanerozoic Eon
Cretaceous Period
Mesozoic
Era
Age of
Mammals
Jurassic Period
Age of
Reptiles
Triassic Period
(Dinosaurs)
Paleozoic
Era
Mass Extinction
1st Flowering Plants
First Birds
Pangaea Breaks Apart
Largest Mass
Extinction
Permian Period
Pennsylvanian
Period
First Humans
Age of
Amphibians
Mississippian Period
First Reptiles
First Amphibians
Silurian Period
Age of
Fishes
Ordovician Period
Age of
Cambrian Period
Invertebrate
s
First Land Plants
First Fish
First Trilobites
Devonian Period
First single celled organisms
Proterozoic means "before animal life" which is
actually not accurate, but most of the organisms were
pretty simple. In addition to bacteria, we find things
like algae and unusual worm-like creatures.
The largest known species of
trilobite waswas found in northern
Manitoba. It measures about 28
inches (72 centimeters) long.
The evidence of microscopic life forms has been
detected as old as 3,700 to 3,800 million years ago.
This evidence was found in Isua greenstone in
Greenland. There have been claims of evidence
dating back as far as 3,850 million years ago but
these are not universally accepted. Scientists
continue to refine dating methods to get reliable data
on the earliest life on earth.
Organic Evolution
The fossil record shows that species have
changed over geologic time.
Environmental changes can affect an
organism’s survival.
Organisms that can not adapt physically or
genetically will not survive.
Fossils were discovered with a
Protoceratops & velociraptor that appeared
to have been fighting when they were
quickly killed. The claw of the raptor was in
the others' stomach as well.
Species
Group of organisms that normally
reproduces with other members of their
group.
Reproduction is the key to the survival
of a species.
There is no evidence that suggests that
the dilophosaurus spit venomous mucus.
Natural Selection
A process by which organisms with
characteristics that are suited to a
certain environment have a better
chance of surviving & reproducing.
Genetic mutations can help or destroy
a species’ survival.
Earth’s History
Precambrian Time
 Earth is about 4.5 billion years old.
 Longest portion of Earth’s history (88%)
including the Hadean, Archaen, &
Proterozoic Eons.
There are plenty of dinosaurs that
haven't been discovered yet.
The only dinosaurs we can know
about are the ones that leave fossil
remains, but fossilization is an
extremely rare process.
Very few rocks are found that date back to 4 billion
yrs ago.
Earth was a ball of magma for at least a billion yrs.
If you were to write a history of the
Earth's past, allowing just one page per
year, your book would be 4,600,000,000
pages long. That's a very thick book —
145 miles to be exact.
An average reader, reading about 1 page
every 2 minutes would need more than 17,503
years to finish it.
If you could read 2 pages every second, it
would still take you nearly 73 years
Primitive Atmosphere
• Atmosphere started out as a
lightweight mixture of Hydrogen &
Helium, which drifted out into space.
• It was replaced by large amounts of
Nitrogen, Carbon dioxide, Sulfuric
acid, & small amounts of Water Vapor
(from volcanoes.)
• Eventually the Earth cooled and the
rain formed the primordial oceans.
Precambrian Life
• The first organisms to form on Earth
(3.5bya) were bacteria that lived in
the toxic oceans feeding on sulfur
chemicals.
• Cyanobacteria used chlorophyll for
photosynthesis to make food &
produce Oxygen.
• Fossils of cyanobacteria are called
stromatolites.
Dinosaurs (almost certainly) evolved into birds.
• Over millions of years, the levels of Oxygen
increased in the oceans & atmosphere.
• Current Atmosphere = 79% Nitrogen
20% Oxygen
1.0% Argon
Water Vapor
CO2 & other
Some dinosaurs may have been warm-blooded.
Paleozoic Era (544 mya to 248 mya)
Paleozoic Life
Trilobite
• Invertebrate animals populate the
oceans at the beginning of the Paleozoic
Era. Trilobites are the most abundant.
• Prehistoric bony fishes become the
most abundant organism during the
middle of the Paleozoic.
Placoderm
Most dinosaurs were vegetarians.
• Amphibians take control at the end
of the Paleozoic.
Eryops
• Ferns & cone-bearing plants
(Gymnosperms) grow on land.
• Early forms of reptiles first appear
on land near the end of the
Paleozoic.
Crinoid (Sea Lily) animal not plant!
Paleozoic Geology
• Pangaea forms near the end of the Paleozoic.
• The largest mass extinction in Earth’s history
kills 90% of all marine life & 70% of land species
(250 mya Permian Period.)
Mesozoic Era (248 mya to 65 mya)
Mesozoic Life
• Reptiles (Dinosaurs) most abundant
organism on Earth.
• Reptiles are the 1st vertebrate to live
entirely out of the water.
• The 1st mammals appear during the
Triassic Period
• The 1st birds evolve from dinosaurs
during the Jurassic Period.
• The 1st flowering plants
(Angiosperms) evolve during the
Cretaceous period.
Mesozoic Geology
• Pangaea breaks apart into Gondwanaland &
Laurasia during the early Mesozoic.
• K-T boundary: The 2nd largest mass extinction in
Earth’s history kills many marine & land species
including the dinosaurs.
More than 90 percent of all organisms
that have ever lived on Earth are
extinct.
• Many factors could have led to the extinction:
 Plate Tectonics causing climate changes
 Comet/Asteroid hit the Earth
 Blocking out of the Sun
 Cooling temperatures
 Starvation
Not all dinosaurs were equally dumb.
It's true, some plant-eating dinosaurs
(like Stegosaurus) had brains so tiny
compared to the rest of their bodies that they
must have been only a little bit smarter than
giant ferns. But predatory dinosaurs large and
small, ranging from Troodon to T. Rex, had
more respectable amounts of grey matter,
since they needed better-than-average sight,
smell, agility and coordination to hunt down
prey. (Let's not get carried away, though-even the smartest dinosaurs were only on an
intellectual par with modern ostriches,
nature's D students.)
Cenozoic Era (65 mya to present day)
Cenozoic Life
• Mammals become the most dominant
organism on Earth.
• 3 groups of mammals evolve:
 Monotremes
 Marsupials
 Placentals
• The largest of the mammals becomes extinct
during the Cenozoic.
• Homo sapiens appear about 140,000 years ago
(according to the fossil record) and becomes the
most dominant/complex animal.
Dinosaurs lived at the same time as mammals, but not humans.
Fossils
Principle of Superposition
 In undisturbed rock layers, the oldest layers
of rock are on the bottom.
 Rock layers can be ranked by relative age.
Red Sandstone
Dinosaur bone
Tan Limestone
Megalodon is estimated to
have been 40 to 50 feet long
and weigh 48 tons!
Gray Limestone
Tan Sandstone
Black Shale
Brown
Sandstone
Brown
Sandstone
small fossil
Green Shale
Pterosaurs and
aquatic reptiles
weren't technically
dinosaurs.
Gray Shale
Dike
Trilobite fossil
Forming Fossils
 An organism must be buried quickly
to form a fossil.
 Hard parts dissolve to leave a mold.
 A cast is formed when a mold fills w/
sediment or minerals.
 Thin carbon films remain in the
shapes of dead organisms.
Fossil Type
Description
Mold
hollow impression of a living
thing in rock after it rots
away
Cast
solid mineral deposit that
filled a mold, leaving a copy
of the living thing
Imprint
an impression in rock made
by a living thing during its
life activities
Petrification
plant or animal tissue
replaced by minerals
Whole Organism
(not a fossil)
an entire plant or animal
encased and preserved in
ice, sap, or another material
Trace
(not a fossil)
remains of tracks, burrows,
eggs + eggshells, nests,
droppings, etc
Picture
Fossilized poop
Today, many scientists think the evidence indicates a sixth mass extinction is under way. The blame for this one,
perhaps the fastest in Earth's history, falls firmly on the shoulders of humans. By the year 2100, human activities
such as pollution, land clearing, and overfishing may have driven more than half of the world's marine and land
species to extinction.
Dating Fossils
Radioactive Decay
• Some isotopes are unstable
and decay into other isotopes
& particles.
• Decay is measured in halflives, the time it takes for half
of a given isotope to decay.
Parent 1 Half
Life
2 Half 3 Half
Lives Lives
4 Half
Lives
Sauroposeidon may have been the largest dinosaur ever to walk
the face of the earth. Scientists believe this gigantic dinosaur
would have stood 60 feet tall (18 meters) and weighed 60 tonnes!
Sauroposeidon means "earthquake god lizard”. This dinosaur may
also hold the record for having the longest neck.
Radiometric Ages
• The ratio of the parent isotope to daughter
product can be used to determine the absolute
age of the rock.
• Living organisms less than 75000 years old can
be dated using Carbon-14.
A patch of Posidonia oceanica, a species of seagrass native to the Mediterranean, has just
gotten its DNA sequenced and its age determined--and as it turns out, some parts of this
particular patch are up to 200,000 years old. That easily destroys the previous world record
of the oldest living organism, a Tasmanian plant believed to be around 43,000 years old.
The oldest fossils of multicelled animals come from just two
places on earth. The Burgess Shale formation in Canada
was long regarded as the oldest fossil bed. The Burgess
Shale was formed about 530 million years ago during the
Cambrian period. Many early Cambrian Period fossils have
been found there. The Chengjiang Deposits of China are
thought to be even older than Canada’s Burgess Shale. The
fossils are found near the town of Chengjiang, in the Yunnan
Province of China. This area appears to be about 15 million
years older than the Burgess Shale formation.