U1 L2 Fossils and the History of Life Lesson 2 Explore the skeletons of modern organisms along with fossils found in different strata to identify similarities and differences across organisms and make arguments based on evidence. What do fossils reveal about the history of life on Earth? Phenomenon: Dinosaurs once roamed the Earth, but now we do not find them alive anywhere. Dinosaurs are generally considered by scientists today as one of the more successful vertebrates to ever inhabit Earth. Why do you think that is? EX OPP: Research the factors that scientists use to determine dinosaurs to be more successful than other vertebrates. Two common misconceptions are that dinosaurs and humans (cavemen) lived at the same time and that humans caused the extinction of the dinosaur. Dinosaurs had already died off 65 million years before humans had made an appearance on Earth. However, small mammals (including tiny primates) were alive at the time of the dinosaur. It’s a sunny day in Sheep Creek, Wyoming. This young scientist Introduction is brushing away 150 million-year-old rock fragments, carefully digging out the tail bones of an enormous dinosaur called Diplodocus. Besides bones, dinosaurs have also left behind footprints, eggs, and even lumps of preserved feces! But what can scientists learn from fossils? Fossils tell the story of life on Earth. For example, fossils can reveal how the number of living things on Earth has changed over time. You will learn about times when many new kinds of living things originated relatively quickly, as well as about huge mass extinctions in which many living things died out suddenly. What could have caused such massive die-offs? You will then look at how specific groups of living things changed over time. For example, what evidence is there that birds are descended from dinosaurs and that whales are descended from mammals with legs? Throughout this lesson, you will identify patterns in the fossil record by looking at charts, graphs, and images. You will learn a lot about how life appeared, changed, and disappeared. Finally, because many fossils are rare and scientifically valuable, you will learn how scientists are creating detailed copies of important fossils so that they can be more easily studied. 1. Fossils and the Fossil Record P26-27 Scientists learn about the organisms that once lived on Earth from the fossils they leave behind. A fossil is the preserved remains or traces of a once living organism. There are two main types of fossils 1) body fossils 2) trace fossils. 1. Fossils and the Fossil Record P26-27 Body Fossils Trace Fossils Preserve the traces that living things left Formed when the bodies or body parts of behind. organisms are preserved as fossils. Include things like footprints, animal burrows, Provide direct evidence of formerly living toothmarks, and feces. things. Provide indirect evidence of formerly living things. Both can provide a lot of information about how organisms lived. Ex: • Footprints can show how fast an animal walked or ran. • The fossil nests left by certain dinosaurs provide evidence that dinosaurs cared for their young, similar to the way birds do today. 1. Fossils and the Fossil Record P26-27 Body parts or whole bodies can also be preserved as fossils. The soft parts of living things typically decay quickly, so preserved body parts are often hard parts such as bones, teeth, or shells. Sometimes, minerals from groundwater slowly seep into the original bones or shells, replacing the original material and leaving a fossil made of stone. Add to bottom of notes page (space)Steps: How fossils form 1. Fossils and the Fossil Record P26-27 Body parts or whole bodies can also be preserved as fossils. The soft parts of living things typically decay quickly, so preserved body parts are often hard parts such as bones, teeth, or shells. Sometimes, minerals from groundwater slowly seep into the original bones or shells, replacing the original material and leaving a fossil made of stone. Add to bottom of notes page (space)Steps: How fossils form 1. Fossils and the Fossil Record P26-27 Unusual type of body fossil is produced when, in certain rare cases, an entire organism is preserved. Amber Ice 1. Fossils and the Fossil Record P26-27 Earth’s fossils can be placed along a timeline using absolute and relative dating, techniques. The fossil record describes the history of life on Earth as documented by the fossils collected so far. Shows that there have been many changes in the kinds of organisms living on Earth over time. Fossil record does not include every species that has ever lived on Earth. Very few living things actually end up as fossils. 1. Fossils and the Fossil Record Review 2. Order the steps of fossilization from 1 to 5. 1. Match each fossil with its type 3 Layers of sediment cover the bones. Erosion removes rock layers and reveals 5 the fossil. 2 The soft parts of the body rot away. Pressure turns the sediments into rock. The bones slowly decay are and 4 replaced by minerals. 1 An animal dies. 3. Does the fossil record include every species that every lived? Why or why not? No, very few living things actually end up as fossils. Most dead organisms are eaten or decompose before they have a chance to be preserved. Also, some animals without hard body parts might not be preserved at all. 2. Increasing Complexity in the History of Life You and your shoulder partner, Read and take your own notes of Sec 2 P28 When finished do review Then Read Sec 3-4 p29-31 2. Increasing Complexity in the History of Life Earth’s oldest fossils are about 3.7 billion years old. single “simple” cell → complex cells were much larger/had a nucleus → Multicellular Life Increasing complexity is one pattern in the history of life. The fossil record shows that the earliest life forms had a single, simple cell. Over time, more complex cells appeared, followed by multicellular life. However, simple organisms still exist today and are both abundant and successful. The increasing complexity of life over time. Bacterial Cell → Cell with a nucleus → Multicellular organism No, there are many "simple" organisms still alive today. INVESTIGATION 1 INTERPRETING FOSSILS Scientists have found fossils, like these, How do we know that dinosaurs once of organisms that look different from existed? organisms that are alive today. INVESTIGATION 1 INTERPRETING FOSSILS 1) What do you think you can tell about an organism or its environment from fossilized bones? You can often tell many things about an organism from its fossils, like its general structure and size. Depending on the parts you find, you might also be able to tell what it ate, how it moved, how it reproduced, where it lived, how it interacted with other organisms. You would not be able to tell what it What can you not tell? sounded like. And, in general, you might not be able to tell much about its soft body parts, its color, or its daily behaviors. INVESTIGATION 1 INTERPRETING FOSSILS In this activity you are going to draw conclusions about modern- day organisms and their environment based on their skeletons. In pairs you will: Analyze skeletons of modern-day organisms. Work in pairs and pick up Handout A. Use logic to develop explanations about each organism and its environment. INVESTIGATION 1 INTERPRETING FOSSILS Now, you will use the same skills you just used in the previous activity to draw conclusions about fossilized organisms and their environment. In general, science assumes that the same skills you use to understand organisms now can be used to understand organisms that lived in the past because the assumption is that natural laws operate today as in the past. INVESTIGATION 1 INTERPRETING FOSSILS Now, you will use the same skills you just used in the previous activity to draw conclusions about fossilized organisms and their environment. Analyze fossils of ancient organisms. Visit each station in the room and analyze each fossilized organism from Handout B. Use logic to develop explanations about each organism and its environment. Record all the information in your notebook. INVESTIGATION 1 INTERPRETING FOSSILS Wrap Up 3. Why are you more likely to find fossils of organisms that lived in water than land-based organisms? Fossils are formed in sedimentary rock which develops only near water. 4. What can you tell about an organism or its environment based on its fossilized remains? You can tell its size, general shape, the type of environment it might have lived in, and what kind of food it ate. 5. What can you NOT tell about an organism or its environment based on its fossilized remains? You cannot tell the noises that it makes or its smell. 3. Increases in the Diversity of Life At times in Earth’s history, biodiversity on Earth increased suddenly. One example of this was during the Cambrian Explosion. In this photo, scientists are excavating fossils from the time of the Cambrian Explosion. Rock strata from the time of the Cambrian Explosion provide fossil evidence of the origin of most of the major groups of animals found on Earth today. 3. Increases in the Diversity of Life The term biodiversity describes the variety of species on Earth. scientists have observed a sudden, rapid increase in biodiversity. adaptive radiation— “adaptive” because the new species are well suited to living in their environments “radiation” because many species appear quickly, as if spreading out from a single point. 3. Increases in the Diversity of Life The Cambrian Explosion most likely resulted from a combination of factors.