Geologic Time Scale 2010
Name: TEACHER'S NOTES Period: ____
Purpose/Objectives:
As a class, you will calculate the proper order of significant biological events
and place them along a to-scale timeline of Earth’s history. By the end of this
activity you should be able to:




Understand the magnitude of geologic time
Explain why the geologic time scale is used to show Earth’s history.
Describe what early Precambrian organisms were like.
Describe the major events of the Paleozoic, Mesozoic, and Cenozoic Eras.
Activity:
To determine the placement of “Major events” along the transect, divide the
date of the event by 100 to get the distance in meters. See the example below:
Event
Date (MYA)
Distance (m)
Formation of Earth
4600
4600 ÷ 100 = 46 meters
Questions:
1. Why is a time scale used to represent Earth’s history instead of a calendar?
A calendar would be hard to use because Earth’s history is so long.
2. Which Era takes up the most space? Precambrian time.
3. What major event marked the beginning of the Paleozoic era?
Many different kinds of organisms evolved.
4. In what order did fishes, amphibians, and reptiles evolve?
Fishes, amphibians, reptiles.
5. What major event marked the end of the Paleozoic Era?
A mass extinction occurred.
6. What major life forms dominated the first part of the Mesozoic Era?
Reptiles.
1
Minority Science Programs – School of Biological Sciences – University of California, Irvine
Geologic Time Scale 2010
Major Events Table:
Event
Date
(million years ago)
Distance
(meters)
Precambrian
Formation of Earth
4600
46
Precambrian
Origin of life (Bacteria)
3500
35
Precambrian
First multicellular organisms
1000
10
Precambrian
First green algae (plants)
700
7
Precambrian
First animals (sponges & jellies)
600
6
Era
Period
Paleozoic
Cambrian
Cambrian Explosion (many invertebrate
sea animals evolved at once)
543
5.43
Paleozoic
Ordovician
First fishes (jawless)
455
4.55
Paleozoic
Silurian
Ordivician extinction (2nd most
devastating extinction to marine life)
440
4.40
Paleozoic
Devonian
First land plants (mosses)
400
4
Paleozoic
Devonian
First insects
396
3.96
Paleozoic
Devonian
First land vertebrates (amphibians)
365
3.65
Paleozoic
Devonian
First seed plants
362
3.62
Paleozoic
Devonian
Devonian extinction (marine
invertebrates)
360
3.6
Paleozoic
Carboniferous
First ancestors of reptiles & birds
340
3.4
Paleozoic
Permian
First ancestors of mammals
285
2.85
Paleozoic
Permian
Permian extinction (90% of all life dies
off; major terrestrial extinctions)
245
2.45
Mesozoic
Triassic
First dinosaurs
225
2.25
Mesozoic
Jurassic
First mammals
200
2
Mesozoic
Jurassic
First birds
150
1.5
Mesozoic
Cretaceous
First flowering plants
85
0.85
Mesozoic
Cretaceous
Cretaceous-Tertiary (K-T) extinction
65
0.65
Cenozoic
Tertiary
First primates (monkeys)
55
0.55
Cenozoic
Tertiary
First apes
30
0.3
Cenozoic
Quaternary
Homo sapiens evolves
0.1
0.001
Cenozoic
Quaternary
Today
0
0
2
Minority Science Programs – School of Biological Sciences – University of California, Irvine
Geologic Time Scale 2010
ACTIVITY INSTRUCTIONS:
Prepare a class set of note cards that include the name of each significant
biological event on one side and the corresponding date (and distance) on the
reverse side. Lay down a 50-meter transect or tape measure outside the classroom
to function as the timeline.
Introduce the activity by discussing timelines (we referenced the “Biological
Events” timeline from their book), emphasizing that many timelines are not drawn
to scale. Explain that you will work as a class to create a to scale timeline of
Earth’s History. After the students have completed all the distance calculations
themselves, distribute the note cards so that each student has one event. Explain
the orientation of the timeline, and then ask each student to place his or her event
at the correct location. Once all the events are placed, walk as a class from one end
of the timeline to the other to observe the proportional passage of time between
events. Ask the students for their observations.
If you have more students than events, you can make cards to mark the
beginning and end of each Era. Assign some students to stand behind the timeline
holding these markers while the others place their events at the correct location.
3
Minority Science Programs – School of Biological Sciences – University of California, Irvine