Download Notes – Early Earth History

Notes – Early Earth History
Chapter 8 Section 2
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Life on Earth Changes
Paleontologists discovered that the system used to _____________________ modern
organisms could be used to classify _____________________.
Fossils from rock layers that are touching are more _____________________ than fossils from
widely separated layers.
The more recent a fossil was formed, the more it _____________________ a living organism.
Precambrian Time
Precambrian rocks are difficult to study because they have undergone
_____________________ or been destroyed.
Precambrian fossils are not abundant but provide a lot of information about Earth’s early
_____________________ and _____________________.
The Precambrian Atmosphere
Archean _____________________ contain large amounts of pyrite and uraninite.
Today’s atmosphere contains _____________________ that quickly destroys these minerals
through _____________________.
Earth’s early atmosphere had very _____________________ oxygen.
Ozone
The absence of oxygen suggests there was no _____________________ layer during
_____________________ time.
Without ozone, ultraviolet rays cause death or _____________________ in cells.
Changes in one gene in an organism could result in _____________________ life forms many
generations later.
The First Organisms
Cyanobacteria—one of the _____________________ organisms.
Stromatolites are mounds of alternating thin-layered sediments and _____________________
cyanobacteria that take in carbon dioxide and release _____________________.
A Changing Environment
Oxygen levels _____________________ slowly as _____________________ and other earlylife forms released oxygen.
Natural _____________________ favored organisms that could tolerate or use
_____________________.
The amount of ozone in the atmosphere _____________________.
Soft-Bodied Organisms
The first invertebrate organisms—animals _____________________ backbones—appeared
during the _____________________ eon.
o Ediacaran fauna
The Paleozoic Era
The first appearance of fossils of organisms made from _____________________ parts marks
the end of the Proterozoic eon.
Because hard parts fossilize easier, fossils are easier to find in _____________________ rocks
than Precambrian rocks.
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The Cambrian Explosion
During a relatively short period of time, the number of animals with
_____________________ greatly _____________________.
Invertebrates—sponges, jellies, _____________________—also evolved during the
_____________________ explosion.
Invertebrates of the Paleozoic Era
Throughout the Paleozoic era, the oceans contained a wide variety of
_____________________ organisms.
Corals, brachiopods, crinoids, bryozoans
Ordovician period, Silurian period
Vertebrates of the Paleozoic Era
Vertebrates—animals _____________________ backbones—evolved during the early
Paleozoic era.
The first of these lived in the _____________________.
o Bony fish with bony rays that supported their fins
o Bony fish with thick fins supported by large _____________________ and muscles
A New Egg
A new organism that could lay its _____________________ on land evolved during the early
_____________________ period.
Amniotes laid water-tight, amniotic eggs and could spend all their time on
_____________________.
o Mammals, _____________________, and reptiles evolved from amniotes.
Plants of the Paleozoic Era
During the Ordovician period, _____________________ began spreading onto
land.
Early land plants were small and lived in _____________________ areas because
they could not move water to all their parts.
Plants with _____________________ systems that could move nutrients between
roots and leaves then evolved.
o New plants _____________________ quickly.
Paleozoic Extinctions
The Paleozoic era ended with the late _____________________ extinction—
_____________________ of marine and 70% of _____________________ species.
The uplifting formation of _____________________, or ash and _____________________
released from the Siberian Traps may explain the Permian extinction.