Chapter 7 Lesson 3

Science Essential Question How does a system of living and non-living things operate to meet the needs of the organisms in an ecosystem? Science Essential Question

Vocabulary For Today Page B76 Era – a major division of time defined by events that took place during that time Fossil – the preserved traces and remains of an organism that lived long ago Paleontologist- a scientist who studies fossils

MAIN IDEA Scientists study fossils to learn about the history of Earth and its organisms.

Making a Fossil Mold a piece of clay into a thick, flat layer. Press an object into the clay until the object makes an imprint. Carefully remove the object. Exchange imprints with a partner. Do not let your partner see the object that you used to make the imprint. Use a hand lens to look closely at your partner’s imprint. Record your observations in your Science Notebook. Try to identify the object that was used to make your partner’s imprint. Exchange objects with your partner. Record the similarities and differences between your partner’s object and the imprint made from it. Think about what can be seen from the imprint and what cannot.

Why Scientists Study Fossils Page B76 Studying fossils give scientists some clues about what the Earth was like millions of years ago. A fossil is the preserved traces and remains of an organism that lived long ago. Fossils can include bones, teeth, shells, and imprints, or impressions of organisms that were pressed into mud and sand. In studying fossils, scientists learn what animals looked like and what they ate.

Classifying Fossils Page B77 A scientist who studies fossils is called a paleontologist. Part of a paleontologist’s job is to classify organisms from their fossils. The paleontologist uses what is known about today’s plants and animals to study fossils. How deep a fossil is found in a layer of rock can be a clue to its age. Other clues can tell what an organism looked like or how it behaved.

Making a Hypothesis Scientists gather as many facts as they can about the fossil and the organism that produced it. They use these facts to make a hypothesis. As they gather more facts, they may later change their hypothesis.

Fossils and the Present Most species that were alive millions of years ago are now extinct. Paleontologists look for relationships between fossils of extinct species with species alive today to compare how they are alike and different.

Dating Fossils Paleontologists date fossils in different ways: Measuring how much carbon is in a fossil containing bone can indicate the fossil’s age. Scientists also look at how deeply a fossil is buried within layers of rock. The deeper a fossil is buried, the older it is likely to be. Scientists have made a timeline called the geologic time scale. It shows important events in Earth’s history and gives information about the kinds of organisms that lived at different times.

Eras The time scale is broken down into sections called eras. An era is a major division of time. Each era lasted many millions of years. An era is defined by events that took place during that time. Mesozoic Era – Reptiles like dinosaurs Cenozoic Era – Mammals, including humans began to appear

Why Scientists Study Fossils From your notes and by reading page B76, can you answer these questions? What is a fossil? What can fossils include? Why do scientists study fossils? Discuss the answers to these questions in your groups.

Classifying Fossils From your notes and by reading page B77, can you answer these questions? What is a paleontologist’s job? If a paleontologist found a fossil with flat teeth, what could be concluded about the fossil? Explain how the pterosaur got classified as a flying reptile. Discuss the answers to these questions in your groups.

Fossils and the Present From your notes and by reading page B78, can you answer these questions? What are some relatives of today’s elephant? Describe them. Why do paleontologists compare fossils of extinct species to species that are alive today? Most of the animals that were alive millions of years ago are now extinct. What has caused this? Discuss the answers to these questions in your groups.

Dating Fossils From your notes and by reading page B79, can you answer these questions? What is a geological time scale? What is an era? How long did an era last? Compare the animals that lived in the Cenozoic Era and the Mesozoic Era. Discuss the answers to these questions in your groups.

Video Time Let’s watch the BrainPop Video – Fossils.