Deep Time

Lesson Plan for Grades 9-12

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Resources for this Lesson:

Deep Time
(Interactive)

Evolution on Double Time
(Document)

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Overview

Part of the reason evolution may be a difficult topic to grasp is that it takes place very gradually over a long period of time. Understanding geologic, or "deep," time helps students understand evolution. In this lesson, students learn about deep time by visiting an interactive Web timeline, comparing geologic time periods to the familiar calendar year, and setting up a live-action student timeline in the classroom.

Objectives

Understand the geologic time scale
Learn about the transformations, extinctions, and geologic changes that occurred in Earth's history

Suggested Time

Two to three class periods

Multimedia Resources

Deep Time Flash Interactive
Evolution on Double Time HTML Document

Materials

Calendar
Calculator

The Lesson

Part I: Exploring Deep Time

1. Have your students visit the Deep Time Web activity. This interactive timeline allows them to choose any time period in Earth's 4.6-billion-year history and learn about the transformations, extinctions, and geologic changes that took place then.

2. As students proceed, have them jot down notes on the following questions, which are organized according to the three themes of the activity's timeline:

Transformations

How does fossil evidence demonstrate that species have changed over time?
What are some of the major transformations in the evolution of life?
What kinds of fossils would you expect to find in the Cambrian strata of rocks such as the Burgess Shale?
What could account for the Cambrian explosion?
Why is it difficult to demonstrate the gradual transformation of one species into another using the fossil record?
What kinds of fossils are more likely to show such transformations? Why?
What fossil examples of such transformations have been discovered?

Extinctions

When did mass extinctions occur, and what organisms were affected?
What is the significance of extinction for the evolution of existing organisms?

Geologic Changes

How did the continents change from the Precambrian to the Permian to the Jurassic to the Eocene?
How could the shifting of continents have influenced the distribution and migration of plants and animals?

3. Discuss the answers with the class.

Part II: Live-Action Student Timeline

4. Ask students to define the following words: eon,era,period, and epoch.

5. Now ask students to think of the geologic time scale in terms of a calendar year, that is, 4.6 billion years of Earth's history as equivalent to twelve months. Tell them they are going to calculate where during the calendar year the geologic time periods listed below fall. This exercise will give them a sense of how recently humans evolved.

6. Establish the start of the Precambrian eon (4.6 billion years ago) as January 1 on the calendar, and present day as December 31. Remind students that 4.6 billion years (4,600 million years) is comparable to 365 days, so each day equals 12,602,740 years:

7. Assign one or two students to each of the time periods listed below, and have them figure out the representative calendar days.

` <table border="0" cellpadding="0" cellspacing="0" summary="structural table" align="center"> <tr> <td width="200" align="left" valign="top" height="20"> Precambrian Eon</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 4,600-543 million years ago (Mya)</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Hadean Era</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> >4,550-3,800 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Archaean Era</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 3,800-2,500 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Proterozoic Era</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 2,500-543 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Phanerozoic Eon</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 543-present</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Paleozoic Era</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 543-248 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Cambrian Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 543-490 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Ordovician Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 490-443 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Silurian Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 443-417 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Devonian Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 417-354 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Carboniferous Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 354-290 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Permian Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 290-248 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Mesozoic Era</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 248-65 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Triassic Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 248-206 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Jurassic Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 206-144 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Cretaceous Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 144-65 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Cenozoic Era</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 65 Mya-present</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Tertiary Period</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 65-1.8 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Paleocene Epoch</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 65-54 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Eocene Epoch</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 54-33 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Oligocene Epoch</td> <td width="40" valign="top">  </td> <td width="200" align="left" valign="top" height="20"> 33-24 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Miocene Epoch</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 24-5.3 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Pliocene Epoch</td> <td width="40" valign="top"> </td> <td width="200" align="left" valign="top" height="20"> 5.3-1.8 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Quaternary Period</td> <td width="40" valign="top">  </td> <td width="200" align="left" valign="top" height="20"> 1.8 Mya-present</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Pleistocene Epoch</td> <td width="40" valign="top">  </td> <td width="200" align="left" valign="top" height="20"> 1.8-0.01 Mya</td> </tr> <tr> <td width="200" align="left" valign="top" height="20"> Holocene Epoch</td> <td width="40" valign="top">  </td> <td width="200" align="left" valign="top" height="20"> 0.01-present</td> </tr> </table>

8. You may want to do one example on the board, to get students started. For example, the Carboniferous period dates from 354 to 290 million years ago. If one calendar day equals 12,602,740 years on the geologic time scale, then:

[ <center>354,000,000 / 12,602,740 = 28 days December 31 - 28 days = December 3 290,000,000 / 12,602,740 = 23 days December 31 - 23 days = December 8 </center>

If the geologic time scale were represented by one year, then the Carboniferous period was just five days long, occurring between December 3 and December 8. That's very recently in geologic time.

Remind students that geologic time periods represent millions of years ago, so they must work backwards from December 31. They may want to refer to a calendar to see how many days are in each month.

9. Ask students to visit the Deep Time Web activity, and possibly other sources, to research their assigned time period. Tell them to list the kinds of animals or plants alive at that time, any extinctions that occurred, and information about geology and climate.

10. Next, divide the front of the classroom into twelve equal sections representing the months of the year. Use masking tape to set up a "timeline" in your hallway. Leave about four feet of space for each month. Have students stand in the month that corresponds to their geologic time period and arrange themselves in order by day. Most students will be grouped in the section representing December, showing that most of the divisions of the geologic time scale have occurred relatively recently. That is because more is known about these time periods.

11. Finally, starting with the month of January, have each student shout out his or her time period along with one thing that the time period is known for -- to create a live-action student timeline.

Optional Activity

Part III

12. You may wish to assign the Evolution on Double Time reading as enrichment. It discusses how life evolved from simple organisms with few genes to more complex organisms with several thousand genes in a relatively short period of time through the process of gene duplication.