13.1 Precambrian Time: Vast and Puzzling Precambrian History 13.1 Precambrian Time: Vast and Puzzling  The Precambrian encompasses immense geological time, from Earth’s distant beginnings 4.56 billion years ago until the start of the Cambrian period, over 4 billion years later.  Precambrian Rocks • Shields are large, relatively flat expanses of ancient metamorphic rock within the stable continental interior. • Much of what we know about Precambrian rocks comes from ores mined from shields.

Geologic Time Scale Makes no sense without caption in book

Remnants of Precambrian Rocks Makes no sense without caption in book

13.1 Precambrian Time: Vast and Puzzling Precambrian History 13.1 Precambrian Time: Vast and Puzzling  Earth’s Atmosphere Evolves • Earth’s original atmosphere was made up of gases similar to those released in volcanic eruptions today—water vapor, carbon dioxide, nitrogen, and several trace gases, but no oxygen. • Later, primary plants evolved that used photosynthesis and released oxygen. • Oxygen began to accumulate in the atmosphere about 2.5 billion years ago.

13.1 Precambrian Time: Vast and Puzzling Precambrian History 13.1 Precambrian Time: Vast and Puzzling  Precambrian Fossils • The most common Precambrian fossils are stromatolites. • Stromatolites are distinctively layered mounds or columns of calcium carbonate. They are not the remains of actual organisms but are the material deposited by algae. • Many of these ancient fossils are preserved in chert—a hard dense chemical sedimentary rock.

13.2 Paleozoic Era: Life Explodes Early Paleozoic 13.2 Paleozoic Era: Life Explodes  Following the long Precambrian, the most recent 540 million years of Earth’s history are divided into three eras: Paleozoic, Mesozoic, and Cenozoic.

13.2 Paleozoic Era: Life Explodes Early Paleozoic 13.2 Paleozoic Era: Life Explodes  Early Paleozoic History • During the Cambrian, Ordovician, and Silurian periods, the vast southern continent of Gondwana encompassed five continents (South America, Africa, Australia, Antarctica, and part of Asia).

Gondwana and the Continental Landmasses Makes no sense without caption in book

13.2 Paleozoic Era: Life Explodes Early Paleozoic 13.2 Paleozoic Era: Life Explodes  Early Paleozoic Life • Life in early Paleozoic time was restricted to the seas. Animals developed hard parts, such as shells, for the first time. This provided organisms with protection and an “environment” for body organs to function more efficiently.

Life in the Ordovician Period Cephalopods, trilobites, brachiopods, snails, and corals inhabited the waters of the Ordovician period. trilobites Makes no sense without caption in book squid corals snail

13.2 Paleozoic Era: Life Explodes Late Paleozoic 13.2 Paleozoic Era: Life Explodes  Late Paleozoic History • Laurasia is the continental mass that formed the northern portion of Pangaea, consisting of present-day North America and Eurasia. • By the end of the Paleozoic, all the continents had fused into the supercontinent of Pangaea.

Late Paleozoic Plate Movements Makes no sense without caption in book

13.2 Paleozoic Era: Life Explodes Late Paleozoic 13.2 Paleozoic Era: Life Explodes  Late Paleozoic Life • Some 400 million years ago, plants that had adapted to survive at the water’s edge began to move inland, becoming land plants. • The amphibians rapidly diversified because they had minimal competition from other land dwellers.

Armor-Plated Fish Makes no sense without caption in book Armor-plated fish were common during the Devonian period. These armor-plates are similar to present day fish scales.

Model of a Pennsylvanian Period Coal Swamp Makes no sense without caption in book Large tropical swamps extended across North America, Europe, and Siberia. Trees approached 98 feet tall. The coal deposits that we use today for fuel originated in these swamps.

13.2 Paleozoic Era: Life Explodes The Great Paleozoic Extinction 13.2 Paleozoic Era: Life Explodes  The world’s climate became very seasonal, probably causing the dramatic extinction of many species.  The late Paleozoic extinction was the greatest of at least five mass extinctions to occur over the past 500 million years.

Continental Positions Plant Life Animal Life Early Paleozoic Late Paleozoic Restricted to the seas (invertebrates) Gondwana at the South Pole and other landmasses near the equator Water Plants Fish and amphibians Pangaea Land Plants

13.2 Assessment What are the 7 periods that make up the Paleozoic era? Which life forms dominated the early and late parts of the Paleozoic era? What allowed amphibians to flourish on land? Compare and contrast the life of Early Paleozoic and Late Paleozoic.

Writing in Science Imagine you are uncovering rocks and fossils from a site that formed during the Paleozoic era. Write a paragraph (5-7 sentences) describing what kinds of fossils you would expect to find as you dug from the surface and moved downward. ** Remember the Law of Superposition

Mesozoic Era Mesozoic era spanned about 183 million years It is divided into 3 periods: Triassic, Jurassic and Cretaceous

13.3 Mesozoic Era: Age of Reptiles  Dinosaurs were land-dwelling reptiles that thrived during the Mesozoic era.  Mesozoic History • A major event of the Mesozoic era was the breakup of Pangaea. Plate tectonic activity began

13.3 Mesozoic Era: Age of Reptiles  Mesozoic Life When the Mesozoic era began, its life forms were the survivors of the Paleozoic extinction On land, conditions favored life that could adapt to drier climates • Gymnosperms are seed-bearing plants that do not depend on free-standing water for fertilization. (Example: Pinecone) • The gymnosperms quickly became the dominant plants of the Mesozoic era.

Canadian Rockies Were Formed Throughout the Cretaceous Period Makes no sense without caption in book

13.3 Mesozoic Era: Age of Reptiles  The Shelled Egg • Unlike amphibians, reptiles have shell-covered eggs that can be laid on the land. • The elimination of a water-dwelling stage (like the tadpole stage in frogs) was an important evolutionary step.

13.3 Mesozoic Era: Age of Reptiles  Reptiles Dominate • With the perfection of the shelled egg, reptiles quickly became the dominant land animals. • At the end of the Mesozoic era, many reptile groups became extinct. Only few types of reptiles survived to recent time, including the turtles, snakes, crocodiles and lizards.

Most scientists believe that extinction of these reptiles was caused by a large meteorite that collided with Earth. They believe this collision created huge quantities of dust that blocked out the sun, causing plants to die b/c they could not turn sunlight into food Without plants the huge herbivores could not find enough to eat and eventually could not survive and then carnivores could no longer find food.

The Flying Reptile Pteranodon Makes no sense without caption in book

Fossil Skull of an Extinct Crocodile Makes no sense without caption in book

13.4 Cenozoic Era: Age of Mammals Cenozoic North America 13.4 Cenozoic Era: Age of Mammals  The Cenozoic era is divided into two periods of very unequal duration, the Tertiary period and the Quaternary period.  Plate interactions during the Cenozoic era caused many events of mountain building, volcanism, and earthquakes in the West.

13.4 Cenozoic Era: Age of Mammals Cenozoic Life 13.4 Cenozoic Era: Age of Mammals  Mammals—animals that bear live young and maintain a steady body temperature— replaced reptiles as the dominant land animals in the Cenozoic era.  Angiosperms—flowering plants with covered seeds—replaced gymnosperms as the dominant land plants.

13.4 Cenozoic Era: Age of Mammals Cenozoic Life 13.4 Cenozoic Era: Age of Mammals  Mammals Replace Reptiles • Adaptations like being warm blooded, developing insulating body hair, and having more efficient heart and lungs allow mammals to lead more active lives than reptiles.

Fossils from La Brea Tar Pits Makes no sense without caption in book

13.4 Cenozoic Era: Age of Mammals Cenozoic Life 13.4 Cenozoic Era: Age of Mammals  Large Mammals and Extinction • In North America, the mastodon and mammoth, both huge relatives of the elephant, became extinct. In addition, saber-toothed cats, giant beavers, large ground sloths, horses, camels, giant bison, and others died out on the North American continent. • The reason for this recent wave of extinctions puzzles scientists.

Geologic Time Scale Review Plant Life Animal Life Continental Position Early Paleozoic Late Paleozoic Mesozoic Cenozoic Water Plants Restricted to seas Gondwana Amphibians Land Plants Pangaea Pangaea breaks up Gymnosperms (seeds) Reptiles Angiosperms (flowers) Mtn. building & earthquakes Mammals