Fossil Organisms and their Environment

In this lesson, students apply their knowledge of the interdependence of living things and their environments to analyze fossils, making connections between the types of organisms that lived long ago and their environments. They analyze how fossils provide evidence for changing environments over time.

• Scientists analyze fossils to learn about past life on Earth, as well as past environmental changes.
• Scientists can determine a fossil’s age based on where it is found relative to other fossils.
• Scientists study the fossil record, which includes all of the fossils that have ever been found, to understand Earth’s history.

• Why is the body of a dead insect not a fossil?
• Why are fossils important for understanding Earth’s history?
• How do scientists know that some organisms lived a long time ago but are no longer found anywhere?
• Why are there so few fossils compared to the billions of organisms that have lived on Earth?
• How are fossils formed?
• How does a fossil’s position in a rock layer tell scientists about the environment in which the organism once lived?
• Why were scientists surprised to discover the skeleton of a whale in the Sahara?
• What did the discovery of the whale tell scientists about the history of the Sahara?

Misconception: Ecosystems do not change much over time.

Fact: Ecosystems change for a variety of reasons, including environmental changes and human activity.

Misconception: The organisms in an ecosystem are not part of a larger whole, but instead are just a collection of living things surviving independently of one another and their environment.

Fact: Ecosystems are systems, made up of smaller interacting parts. Both the living and nonliving parts of an ecosystem influence the overall ecosystem.

Biome : a specific geographic area with a particular climate that supports different kinds of organisms

Conservation : the study of how to protect organisms and their ecosystems

Decomposer :an organism that breaks down organic material and feeds on the nutrients

Deforestation : removal of trees by humans

Ecosystem : a community of different organisms that depend on interacting with each other and their physical environment for survival

forest : an area of land covered by trees

Fossil : the remains of ancient animals and plants, the traces or impressions of living things from past geologic ages, or the traces of their activities

Fossil Record : all of the fossils that have ever been found, which scientists use to understand Earth’s history

Whales in the Sahara
The Valley of the Whales

More than 100 years ago, scientists in the Sahara made a surprising discovery. They found the skeleton of a whale. Whales are animals that live in the ocean. But the skeleton was clearly that of a whale. And it was buried in the sands of the desert.

Scientists now know that the Sahara hasn’t always been the world’s largest hot desert. Millions of years ago, an ocean covered what is now a desert biome.

Scientists learned about this change in part by studying fossils. Fossils can be the remains of ancient animals and plants. They can also be the traces or impressions of living things from past geologic ages, or the traces of their activities. Fossils include bones, teeth, wood, and shells. Another kind of fossil, called a trace fossil, is an imprint or evidence of a living thing left behind in rock.

Fossils tell scientists about the kinds of organisms that lived long ago. They also tell about the environment the organisms lived in.

How Fossils Form

Fossils are not easy to make. Out of the billions of creatures that have lived on Earth, only a small number have turned into fossils.

Fossils take millions of years to make. The remains of living things can become trapped in layers of rock that build up over time. These remains include whole plants and animals. They also include traces of organisms such as footprints. Over millions of years, heat and pressure turned these remains into fossils. Because of this process, the fossils in lower layers of rock are older than fossils in higher layers.

As the main activity of this lesson, students examine fossil samples found at a simulated dig site in the Sahara to analyze the fossilized organisms and make inferences about their environment. Students examine five different fossils, connecting each fossil with the biome in which it lived. Students use the evidence they gather in the fossil investigation to make inferences about how the environment had changed over time, and how those changes impacted the living things found there.