Warm Up 11508 1 The most common Precambrian

Warm Up 1/15/08 1. The most common Precambrian fossils are layered mounds of calcium carbonate called ____. a. prokaryotes c. stromatolites b. trilobites d. chert 2. Most of the molecular oxygen in the early atmosphere of Earth resulted from a. decaying primitive plants and animals. b. volcanic eruptions. c. lightning striking Earth. d. photosynthesis in primitive plants. 3. How far back does the fossil record extend? a. 3 million years c. 560 million years b. 1 billion years d. 3. 5 billion years Answers: 1) c. 2) d. 3) d.

Paleozoic Era: Life Explodes Chapter 13, Section 2

Paleozoic Era § Following the long Precambrian, the most recent 540 million years of Earth’s history are divided into three eras: Paleozoic, Mesozoic, and Cenozoic § By the beginning of the Paleozoic era, the fossil record has abundant ocean-dwelling organisms that required oxygen to live § This shows that Earth’s atmospheric composition changed with its evolving life forms § Before the Paleozoic, life forms possessed no hard parts (shells, scales, bones, etc) § The Paleozoic era contains many more diverse fossils due to the emergence of life forms with hard parts

Early Paleozoic History § The early Paleozoic consists of a 123 -million-year span that includes the Cambrian, Ordovician, and Silurian periods § During the Cambrian, Ordovician, and Silurian periods, the vast southern continent of Gondwana encompassed five of today’s continents (South America, Africa, Australia, Antarctica, and parts of Asia) § The exact positions of the northern continents are not known, but are thought to have been around the equator § At the beginning of the Paleozoic, North America was a land with no living things, plant or animal § A mountain building event occurred and over 200 million years later the Appalachian Mountains were formed

Earth in Early Paleozoic Time

Concept Check § Why are more fossils found from the Paleozoic era than Precambrian time? § There were more organisms with hard parts, which greatly enhanced a lifeform’s chance of being preserved in the fossil record.

Early Paleozoic Life § Life in the early Paleozoic time was restricted to the seas § Vertebrates had not yet evolved, so life consisted of several invertebrate groups § The Cambrian period was the golden age of trilobites; more than 600 types of these mud-burrowing scavenger flourished around the world § By Ordovician times, brachiopods outnumbered trilobites, and are among the most widespread of Paleozoic fossils § The Ordovician also marked the appearance of the first cephalopods—mobile and highly developed mollusks that became the major predators of the time (squid and octopus are modern day descendents) § The beginning of the Cambrian marks a turning point in animal evolution, with the creation of exoskeletons (hard parts)

Early Paleozoic Life In the image above, trilobites (1) live among many species that are not normally preserved. A typical Cambrian outcrop might produce only trilobites, brachiopods (2), mollusks (3), and crinoids (4). That is a tiny fraction of the full Cambrian biota, better represented by the roster of the Burgess Shale Cambrian Konservat-Lagerstatten. That community includes sponges Vauxia (5), Hazelia (6), and Eifellia (7); brachipods Nisusia (2); priapulid worms Ottoia (8); trilobites Olenoides (1); other arthropods such as Sidneyia (9), Leanchoilia (10), Marella (11), Canadaspis (12), Helmetia (13), Burgessia (14), Tegopelte (15), Naraoia (16), Waptia (17), Sanctacaris (18), and Odaraia (19); lobopods Hallucigenia (20) and Aysheaia (21); mollusks Scenella (3); echinoderms Echmatocrinus (4); and chordates Pikaia (22); among other oddities, including Haplophrentis (23), Opabinia (24), Dinomischus (25), Wiwaxia (26), Amiskwia (27), and Anomalocaris (28).

Concept Check § How did the formation of hard parts benefit animals? § Hard parts allowed animals to venture into different environments.

Late Paleozoic History § The late Paleozoic consists of four periods—the Devonian, Mississippian, Pennsylvanian, and Permian —that span about 160 million years § As ancestral North America collided with Africa, it deformed rocks to produce the Appalachian Mountain of eastern North America § During the union of North America and Africa, the other northern continents began to join § By the Permian period the northern continent of Laurasia was created, made up of present-day North America, Europe, and western Asia § As Laurasia was forming, Gondwana moved northward, and by the Pennsylvanian period it was colliding with Laurasia § By the end of the Paleozoic, all the continents had fused together into the supercontinent of Pangaea

View of Earth—Devonian Period (410 MA)

View of Earth—Mississippian Period (330 MA)

View of Earth—Permian Period (260 MA)

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 earliest land plants were leafless vertical spikes about the size of your index finger § By the end of the Devonian, 40 million years later, the fossil record indicates the existence of forests with trees tens of meters high § In the oceans, armor-plated fishes that had evolved during the Ordovician continued to adapt (with the armor thinning to light-weight scales) § By the late Devonian, several fish became adapted to land environments, becoming amphibians with the ability to breath air § The amphibians rapidly diversified because they had minimal competition from other land dwellers

Late Paleozoic Life

Concept Check § What allowed amphibians to flourish on land? § Amphibians were able to colonize areas that other animals were not. The lack of competition for resources allowed amphibians to be successful.

The Great Paleozoic Extinction § The redistribution of land to form Pangaea, at the end of the Paleozoic, caused drastic changes in Earth’s climate § Broad areas of the northern continents became elevated above sea level, and the climate became drier § These climate changes are believed to have triggered extinctions of many species on land sea § By the close of the Permian, 75% of amphibian families had disappeared, and plants had declined in number and variety § Although many of the amphibian families would become extinct, their descendents, the reptiles, would become the dominant life form on Earth § Much of the marine life did not adapt and survive, with estimates ranging from 80 -95% extinction of marine life § The late Paleozoic extinction was the greatest of at least 5 to occur over the last 500 million years § Mass extinctions actually allowed life to flourish on Earth, as the few survivors eventually filled more niches than the ones left by the victims

Assignment § Read Chapter 13, Section 2 (pg. 369 -376) § Do Section 13. 2 Assessment #1 -6 (pg. 376)