Each student must actively participate in the class/group discussions and activities in order to be successful. To assess student progress, provide feedback to the student, and address student needs, do the following:

• Provide feedback to ensure student understanding through the group discussions and the construction of the prehistoric animal poster.

• Observe students during discussion and construction of the prehistoric animal poster, providing feedback.

• Collect prehistoric animal posters for individual assessment.

“Today we’re going to explore a very rare type of fossil preservation—preservation in tar pits—to see what these fossils can tell us about the prehistoric plants and animals that once lived in the area.” Assess prior knowledge of tar and tar pits. Differentiate between tar and asphalt, posting similarities and differences in graphic organizer form (Venn diagram or flow chart) on the board. Hand out sections 1 and 2 of the La Brea Tar Pits Museum Guide (S-7-2-2_Tar Pits Museum Guide Section 1.pdf and S-7-2-2_Tar Pits Museum Guide Section 2.pdf).

In general, a tar pit forms when a thick, heavy, natural oil (asphalt) seeps through cracks in rocks in the Earth’s crust and forms pools in low areas of the Earth’s surface. “Tar” is a misnomer for this natural asphalt. Tar is man-made from coal and peat. Asphalt resembles tar in appearance but is a type of crude oil made by natural Earth processes.

Distribute the La Brea Tar Pits worksheet (S-7-2-2_La Brea Tar Pits Worksheet and KEY.doc). Instruct students to use the information on the board to help them answer the first two questions on the worksheet. Monitor students, providing feedback, as they respond to the questions. For example, for the first question: Tar is a man-made substance made from coal and peat, while asphalt is a naturally occurring kind of oil made by Earth processes. For the second question: Tar and asphalt look alike. Asphalt is often called “tar” by mistake.

La Brea Tar Pits: “Let’s take a look at a world-famous fossil site, the La Brea Tar Pits. The asphalt slowed the breaking down of plant and animal remains that fell into the pit, preserving the hard parts as fossils. The remains were buried rapidly (in terms of Earth processes), producing the high quality of fossils found in the pit.”

“The La Brea Tar Pits are located in the middle of what is now known as Los Angeles, California. They contain more than 3 million fossils from the last ice age in the prehistoric Los Angeles area, some 10,000 to 40,000 years ago.” Assess prior knowledge of plants and animals of that time.

Jigsaw the La Brea Exploration Guide: Group students. Jigsaw an overview of the guide by assigning parts of sections 1 or 2 to each group to read. Then students produce a poster on butcher paper, consisting of a title and a bulleted summary of at least three main points/interesting facts to post for the class.

Facilitate a short class discussion of the jigsaw information, focusing on what the fossils can tell us about the prehistoric plants and animals that lived in the area surrounding the tar pits. Students take notes on the Lab Brea worksheet. For example: The American mastodon was about 8 feet tall and had low, crowned teeth for eating leaves and twigs. The American mastodon was about half the size of the American mammoth and had more teeth in its jaws than the American mammoth.

Students remain grouped. Assign each group a prehistoric animal that was not discussed on the pages for which they produced the jigsaw posting. Take down the jigsaw postings. “Your last assignment is to make a group report on your assigned prehistoric animal. Your report must include the name of the animal, a sketch of the animal, and at least three pieces of information scientists have learned about the animal from its fossilized record from the tar pit. You may use the notes you took on the worksheet as a reference.”

Extension:

• Students investigate the fossil-rich tar pits in Venezuela and compare them to the La Brea Tar Pits in Los Angeles.