Prehistoric Earth
Geologic Time
Time ____________________
Earth’s ____________________ is divided into time units based on:
•
Major ____________________ events
•
Major ____________________ forms
•
Mass ____________________
-____________________- longest time subdivision based on the abundance of certain types of
____________________
-____________________- 2nd longest time ____________________ based on major worldwide
changes in types of fossils. (____________________, Mesozoic, & ____________________)
-____________________3rd longest time subdivision based on types of life that existed
____________________.
-____________________- smallest time subdivision characterized by differences in
____________________ life.
Organic Evolution
-The fossil record shows that species have changed over geologic ____________________.
-______________________________ changes can affect an organism’s survival.
-Organisms that can not adapt ____________________ or ____________________ will not
survive.
Species

Group of organisms that normally ____________________ with other members of
their group.

Reproduction is the key to the ____________________ of a
____________________.
____________________Selection

A process by which organisms with characteristics that are suited to a certain
environment have a better chance of ____________________ &
____________________.

Genetic ____________________ can help or destroy a species’ survival.
Earth’s History
 Pre____________________ Time

____________________ is about 4.5 billion years old.
 ____________________ portion of Earth’s history (88%) including the Hadean,
____________________, & Proterozoic Eons.
 Very few ____________________ are found that date back to 4 billion yrs ago.
 Earth was a ball of ____________________ for at least a billion yrs.
Primitive Atmosphere
• Atmosphere started out as a lightweight mixture of ____________________ &
____________________, which drifted out into space.
• It was replaced by large amounts of ____________________, Carbon dioxide, Sulfuric acid,
& small amounts of Water Vapor (from ____________________.)
• Eventually the Earth ____________________ and the rain formed the
____________________ oceans.
Precambrian Life
• The first organisms to form on Earth (3.5bya) were ____________________ that lived in the
____________________ oceans feeding on sulfur chemicals.
• Cyanobacteria used ____________________ for photosynthesis to make food & produce
____________________.
• Fossils of cyanobacteria are called ____________________.
• Over millions of years, the levels of Oxygen increased in the ____________________&
____________________.
• Current Atmosphere = 79% ____________________, 20% Oxygen, 1.0%
____________________, Water Vapor CO2 & other
 Paleozoic Era (____________________ mya to 248 mya)
Paleozoic Life
• ____________________ animals populate the oceans at the beginning of the Paleozoic
Era. ____________________ are the most abundant.
• Prehistoric ____________________ fishes become the most abundant organism during the
____________________ of the Paleozoic.
• ____________________ take control at the end of the Paleozoic.
• ____________________ & cone-bearing plants (Gymnosperms) grow on land.
• Early forms of ____________________first appear on land near the end of the Paleozoic.
Paleozoic Geology
• ____________________ forms near the end of the Paleozoic.
• The largest ______________________________ in Earth’s history kills 90% of all marine
life & ____________________of land species (Permian Period.)
 Mesozoic Era (248 mya to ____________________ mya)
Mesozoic Life
• Reptiles (Dinosaurs) most ____________________ organism on Earth.
• Reptiles are the 1st ____________________ to live entirely out of the water.
• The 1st ____________________ appear during the Triassic Period
• The 1st ____________________ evolve from dinosaurs during the Jurassic Period.
• The 1st flowering plants (____________________) evolve during the
____________________ period.
Mesozoic Geology
• Pangaea breaks apart into ______________________________ & Laurasia during the early
Mesozoic.
• The 2nd largest ______________________________in Earth’s history kills many marine &
land species including the dinosaurs.
• Many factors could have led to the ____________________:
• Plate Tectonics causing ____________________changes
• ____________________Asteroid hit the Earth
• Blocking out of the ____________________
• ____________________temperatures
• ____________________

Cenozoic Era (65 mya to ______________________________)
Cenozoic Life
• ____________________ become the most dominant organism on Earth.
• 3 groups of mammals evolve:
 ____________________
 Marsupials
 ____________________
 The largest of the mammals becomes ____________________ during the Cenozoic.
 Homo sapiens appear about 140,000 years ago (according to the fossil record) and
becomes the most dominant/____________________ animal.
Fossils
Principle of Superposition
 In ____________________ rock layers, the oldest layers of rock are on the bottom.
 Rock layers can be ranked by ____________________ age.
Forming Fossils
 An organism must be ____________________ quickly to form a fossil.
 Hard parts dissolve to leave ____________________.
 A ____________________is formed when a mold fills w/ sediment or minerals.
 Thin ____________________ films remain in the shapes of dead organisms.
Fossil Type
Description
_______________
hollow impression of a living thing in rock after it rots away
_______________
solid mineral deposit that filled a mold, leaving a copy of the living thing
_______________
an impression in rock made by a living thing during its life activities
_______________
plant or animal tissue replaced by minerals
Whole ___________
an entire plant or animal encased and preserved in ice, sap, or another
material
________________
remains of tracks, burrows, eggs + eggshells, nests, droppings, etc
Dating Fossils
____________________ Decay
• Some ____________________ are unstable and decay into other isotopes & particles.
• Decay is measured in ______________________________, the time it takes for half of a
given isotope to decay.
Radiometric Ages
• The ratio of the parent isotope to daughter product can be used to determine the
____________________ age of the rock.
• Living organisms less than ____________________ years old can be dated using Carbon14.