8-2 Notes – Early Earth History Chapter 8, Lesson 2

Life on Earth Changes Paleontologists discovered that the system used to classify modern organisms could be used to classify fossils.

Life on Earth Changes Fossils from rock layers that are touching are more similar than fossils from widely separated layers.

Life on Earth Changes The more recent a fossil was formed, the more it resembles a living organism.

Precambrian Time Precambrian time is 88% of Earth’s history, and is split into 3 eons: Hadean, Archean, Proterozoic. 88%

Precambrian Time Precambrian rocks are difficult to study because they are rare, and have undergone metamorphism or been destroyed.

Precambrian Time: Archean Eon Archean Eon sediments contain large amounts of the minerals pyrite and uraninite.

Precambrian Time: Archean Eon Today’s atmosphere contains oxygen that quickly destroys these minerals through oxidation.

Precambrian Time: Archean Eon So, we can conclude that Earth’s early atmosphere had very little oxygen.

Precambrian Time: Archean Eon The absence of oxygen suggests there was no ozone layer during Precambrian time.

Precambrian Time: Archean Eon Without ozone, ultraviolet rays from the sun cause death or mutations in cells.

Precambrian Time: Archean Eon Changes in one gene in an organism could result in new life forms many generations later.

Precambrian Time: Archean Eon through Proterozoic Eon Cyanobacteria are one of the earliest organisms, and they undergo photosynthesis.

Precambrian Time: Archean Eon through Proterozoic Eon Stromatolites are mounds of alternating sediments and cyanobacteria that take in carbon dioxide and release oxygen.

Precambrian Time: Archean Eon through Proterozoic Eon Oxygen levels rose slowly as cyanobacteria and other early-life forms released oxygen. Natural selection favored organisms that could tolerate or use oxygen. The amount of ozone in the atmosphere increased.

Precambrian Time: Proterozoic Eon The first invertebrate organisms, animals without backbones, appeared during the Proterozoic Eon. These were called Ediacaran fauna, and looked similar to present-day jellies, worms, and corals.

Phanerozoic Eon: Paleozoic Era The first appearance of fossils of organisms made from hard parts marks the end of the Proterozoic Eon, and the beginning of the Phanerozoic Eon.

Phanerozoic Eon: Paleozoic Era Because hard parts fossilize easier, fossils are easier to find in Paleozoic rocks than Precambrian rocks.

Phanerozoic Eon: Paleozoic Era: Cambrian Period The first period in the Paleozoic Era is called the Cambrian Period.

Phanerozoic Eon: Paleozoic Era: Cambrian Period 5 million years into the Cambrian Period, an event called the Cambrian Explosion occurred. In a short amount of time, the number of animals with shells greatly increased.

Phanerozoic Eon: Paleozoic Era: Cambrian Period Invertebrates such as sponges, jellies, and corals also evolved during the Cambrian explosion. Changes in trilobite body forms matched changes in the environment.

Phanerozoic Eon: Paleozoic Era: Cambrian Period A well-preserved 5-inch trilobite specimen from Morocco that swam in the ocean during the Devonian Period roughly 400 million years ago (evolved for over 300 million years)

Phanerozoic Eon: Paleozoic Era: Ordovician and Silurian Periods Throughout the Paleozoic era, the oceans contained a wide variety of invertebrate organisms, such as including corals and brachiopods.

Phanerozoic Eon: Paleozoic Era: Ordovician and Silurian Periods 10-cm. cockroaches, 74-cm. wingspan dragonflies were found on land in the Silurian Period.

Phanerozoic Eon: Paleozoic Era: Ordovician and Silurian Periods Vertebrates, animals with backbones, evolved during the early Paleozoic era.

Phanerozoic Eon: Paleozoic Era: Ordovician and Silurian Periods The first of these lived in the oceans. Bony fish with thick fins supported by large bones and muscles

Phanerozoic Eon: Paleozoic Era: Ordovician and Silurian Periods Plants began spreading onto land as well. Early land plants were small and lived in moist areas because they could not move water to all their parts.

Phanerozoic Eon: Paleozoic Era: Pennsylvanian Period In order to reproduce, amphibians had to return to the water to lay eggs.

Phanerozoic Eon: Paleozoic Era: Pennsylvanian Period A new organism evolved that could lay its eggs on land.

Phanerozoic Eon: Paleozoic Era: Pennsylvanian Period Amniotes laid water-tight eggs and could spend all their time on land. Mammals, dinosaurs, and reptiles evolved from amniotes.

Phanerozoic Eon: Paleozoic Era: Pennsylvanian Period Plants with vascular systems that could move nutrients between roots and leaves evolved and spread quickly.

Mass Extinctions The Paleozoic Era ended with the late Permian Period extinction: 90% of marine and 70% of land species.

Mass Extinctions 260 million years ago, the uplifting formation of Pangaea, or ash and sulfur released from the Siberian Traps may explain the Permian extinction.

Mass Extinctions We don’t know exactly what happened, but we know global temperatures rose. Global Temperature

Mass Extinctions With most of the larger, predator-type animals going extinct, other organisms could increase in number, and expand around the world...

C iron in minerals quickly oxidized 8.2 Early Earth History A B C D Which is not a characteristic of Earth’s early atmosphere during the Precambrian time? A very little oxygen B no ozone layer C iron in minerals quickly oxidized D organisms were exposed to ultraviolet rays

What were some of the first vertebrates? A brachiopods B trilobites 8.2 Early Earth History A B C D What were some of the first vertebrates? A brachiopods B trilobites C ediacaran fauna D bony fish

What ended the Paleozoic era? A Ordovician extinction 8.2 Early Earth History A B C D What ended the Paleozoic era? A Ordovician extinction B Devonian extinction C Permian extinction D Cambrian extinction

What caused oxygen levels to rise in Earth’s atmosphere? B C D What caused oxygen levels to rise in Earth’s atmosphere? A the presence of photosynthetic organisms B the evolution of bacteria-eating organisms C an increase in the ozone layer D the evolution of organisms that could tolerate or use oxygen

The evolution of amniotic eggs allowed ___. B C D The evolution of amniotic eggs allowed ___. A the spreading of organisms into dry land B the movement of organisms to shallow-water environments C the evolution of amphibians D organisms to live on land and lay eggs in the water

Which does not characterize the Cambrian explosion? A an increase in small-shelled organisms B the evolution of amniotes C an increase in invertebrates D an increase in large-shelled organisms

Events In Earth’s Past (6:11)

Early Earth Organisms Drawings For the 2 eons and the 7 periods with a * after their name, draw and color 1 organism that could be found alive during that time. text p. 326 and 328

Phanerozoic Eon Paleozoic Era Precambrian Time mass extinction Paleozoic Era Permian Period * Pennsylvanian Period * Mississipian Period * mass extinction Devonian Period * Silurian Period * mass extinction Ordovician Period * Cambrian Period * Precambrian Time Proterozoic Eon * Archean Eon * Hadeon Eon