Student Edition California Education and the Environment Initiative Science7 Standard 7.4.g. Extinction: Past and Present California Education and the Environment Initiative Approved by the California State Board of Education, 2010 The Education and the Environment Initiative Curriculum is a cooperative endeavor of the following entities: California Environmental Protection Agency California Natural Resources Agency California State Board of Education California Department of Education Department of Resources Recycling and Recovery (CalRecycle) Key Partners: Special thanks to Heal the Bay, sponsor of the EEI law, for their partnership and participation in reviewing portions of the EEI curriculum. Valuable assistance with maps, photos, videos and design was provided by the National Geographic Society under a contract with the State of California. Office of Education and the Environment 1001 I Street • Sacramento, California 95814 • (916) 341-6769 http://www.CaliforniaEEI.org © Copyright 2011 by the California Environmental Protection Agency © 2013 Second Edition All rights reserved. This publication, or parts thereof, may not be used or reproduced without permission from the Office of Education and the Environment. These materials may be reproduced by teachers for educational purposes. Contents Lesson 1 La Brea Tar Pits: A Case Study of Extinction California Connections: Puzzle in the “Tar” Pits . 2 Lesson 2 Change in Geologic Time Data on Global Temperature . 6 Data on Atmospheric CO2. 7 . Fossil Data by Era and Period. .8 . Lesson 3 Extinction: Rates and Possible Causes Extinction Case Studies . 9 . Lesson 4 Digging Up the Past Fossil Resource Information . 12. Lesson 5 Extinction: in the Present California Threatened and Endangered Species . 14. Lesson 6 Holocene Extinction Event None required for this lesson . California Connections: Puzzle in the “Tar” Pits Lesson 1 | page 1 of 4 Puzzle in the “Tar” Pits Buried in the heart of Los Angeles sits one of the world’s most impressive collections of ice age fossils in the La Brea Tar Pits. These bubbling black pits contain a snapshot of life from between 40,000 and 10,000 years ago. The Spanish word la brea means “the tar,” but the sticky black ooze in these pits is like asphalt, with which we pave some streets. Pieces of a Puzzle to its surface. The animals Fitting the The ocean covered died and decayed there. Pieces Together Los Angeles more than Scientists believe that bones The great number and variety 100,00 years ago. The plants from other dead animals of fossils at La Brea make it a and animals that lived there likely washed into the pits unique site; the tar there has fell to the ocean floor when from nearby streams. When preserved the full spectrum of they died. Over time, they the tar hardened in the Pleistocene life. The millions of became part of the ocean’s cooler winter months, the bones at La Brea come in all sedimentary layers, where bones became sealed in the sizes: the pits contain microfossils they turned into crude oil pits. When summer returned, too small to see with the naked as a result of heat and the the tar softened again, eye, as well as bones from larger pressure of one layer building forming new traps. Today the animals, or megafauna, such as upon another. When the pits contain millions of bones the American mastodon, saber- ocean receded, tar from this and other debris from plants toothed cat, and ancient bison. oil seeped out of the ground and animals. Using fossils as puzzle pieces, and formed pools. More than Scientists did not realize we can assemble a picture of 100 pools, called pits, are the significance of the fossils climate, landscape, and plant found in Los Angeles, though in the pits until approximately and animal life in the Pleistocene. not all are visible. 100 years ago. The first This picture includes evidence Tens of thousands of excavations of the site began of climate change, biodiversity, years ago, the sticky material in 1901. Since then scientists and extinction. trapped animals, especially have collected more than during the warmer summer 3.5 million fossils belonging Evidence of months when it softened to more than 650 species of Climate Change and was hidden by a layer of plants, animals, and insects Modern-day Los Angeles dust and leaves that stuck from the late Pleistocene. experiences a warm, dry 2 CALIFORNIA EDUCATION AND THE ENVIRONMENT INITIATIVE I Unit 7.4.g. I Extinction: Past and Present I Student Edition California Connections: Puzzle in the “Tar” Pits Lesson 1 | page 2 of 4 climate. Microfossils reveal water supply throughout the Water-loving plants and that the late Pleistocene year. The large numbers of animals no longer live in climate was a little different. fish, frog, and turtle fossils Los Angeles. From fossil Although Southern California show that the climate must evidence, scientists estimate was not covered by a have been wet enough to that the climate became glacier during the last ice support the streams and warmer and drier between age, it was still cooler than ponds these animals need to 18,000 and 11,500 years ago. it is today. Seeds from La survive. In fact, the climate Brea fossils include those of Los Angeles during that Evidence of Biodiversity of coast redwoods, incense period may have been much Scientists continue to cedars, and cottonwoods, like the moist, cool climate of use fossils to reconstruct all trees that need a steady present-day San Francisco. the entire ecosystem at La Brea. The collection includes microfossils, such as those of seeds or small insects, large plant eaters (herbivores), meat eaters (carnivores), and even scavengers. Using seed fossils, scientists have identified 158 different plant species. The fossil collection also includes more than one million invertebrates, such as grasshoppers, flies, and scorpions. Small vertebrate fossils from frogs, toads, salamanders, snakes, turtles, and fish number in the thousands. Most of these species still live in California today. Scientists have discovered many large animals in the tar pits. They look at the shape of fossilized teeth and jawbones La Brea Tar Pits, Los Angeles, California to figure out what these CALIFORNIA EDUCATION AND THE ENVIRONMENT INITIATIVE I Unit 7.4.g. I Extinction: Past and Present I Student Edition 3 California Connections: Puzzle in the “Tar” Pits Lesson 1 | page 3 of 4 animals ate. For example, the broad, flat molars of the Columbian mammoth were ideal for grinding grasses. Its relative, the American mastodon, probably dined on leaves and twigs. Other herbivores in the tar include the ancient bison, western camel, and giant ground sloth. Among the large fossils at La Brea, carnivores outnumbered herbivores almost nine to one. Scientists believe this ratio results from the fact that plant eaters trapped in the tar attracted meat eaters to the pits. The carnivores became trapped while feeding on the Hunter in the ice age carcasses. Scavengers, in turn, also became stuck while Bird fossils are less teratorn, are now extinct. feeding. The most common common than fossils of The teratorn is the largest mammal fossil in the pits is a many other animals because bird fossil pulled from La carnivore called the dire wolf. their bones are hollow Brea; it stood more than two- Scientists believe this wolf and fragile, making them feet tall with a wingspan of hunted in packs, as a result less likely to be preserved. more than 10 feet. many of them got trapped at Even so, scientists have one time. Researchers have discovered more than Evidence of Extinction found other carnivore fossils 100,000 bird fossils in La The fossil record at La too, including short-faced Brea’s tar, comprising one of Brea bears witness to the bears, American lions, and the largest collections in the demise of many species saber-toothed cats. Some world. These remains include at the end of the last ice types of carnivores found in ancestors of birds, such as age. Around 12,000 years the pit, such as the bobcat, the California condor, that ago many animals began coyote, and weasel, still live in still live in California. Others, dying out. Scientists know California today. such as the Merriam’s these animals died out 4 CALIFORNIA EDUCATION AND THE ENVIRONMENT INITIATIVE I Unit 7.4.g. I Extinction: Past and Present I Student Edition California Connections: Puzzle in the “Tar” Pits Lesson 1 | page 4 of 4 then because there are no settling North America to a more arid environment. fossils of these animals in about 500 years ago. Some A chain reaction went all the youngest, uppermost scientists think the pets the way up the food web, parts of the tar pits. The of these settlers spread starting with the herbivores. most affected were large the diseases to vulnerable As the herbivores struggled mammals. Large herbivores, wild animals. The second to survive, the carnivores such as the mammoth, possible factor, nicknamed had fewer prey to hunt. mastodon, ground sloth, the “overkill theory,” suggests Some scientists believe ancient bison, and western that humans caused a combination of all three camel, disappeared. extinctions through hunting factors contributed to Carnivores like the dire wolf, too much. Perhaps humans the extinctions. short-faced bear, American killed large herbivores for lion, and saber-toothed cat food, starving the predators What Does This Mean for also went extinct. Scientists that ate the herbivores? the Future? believe one or more of three Scientists at La Brea do The La Brea Tar Pits offer factors—disease, overkill not have much evidence for a unique glimpse of changes by humans, and climate these theories, especially around the end of the last change—may explain this because they have found the ice age.