Activity Set-Up: Reconstructing the Geological Timeline

(adapted from the version created by D. Hemler and T. Repine in the Science Teacher, April 2002)




Time Allotment: Two 50-minute periods

National Science Education Standards:

(Grades 5-8)

·        Millions of species of animals, plants, and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.

·        Biological evolution accounts for the diversity of species developed through gradual processes over many generations. Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment

(Grades 9-12)

·        The great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms.

·        Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms. The millions of different species of plants, animals, and microorganisms that live on earth today are related by descent from common ancestors

·        Evidence for one-celled forms of life –the bacteria—extends back more than 3.5 billion years. The evolution of life caused dramatic changes in the composition of the earth’s atmosphere, which did nor originally contain oxygen.




* alternately, Velcro can be used to attach the cards onto the clothesline. If teachers have access to a magnetic board and magnetic strips, these also work very well in place of the clothesline and pins.



1) Copy the events on Figure 1 onto the card stock or index cards. Make 4 sets of these cards. Adding pictures for the events associated with organisms is helpful.




“Lucy” (Australopithecus afarensis)

4 mya


35 mya


55 mya

Cenozoic Era begins

65 mya


65 mya


100 mya

First flowering plants

125 mya


140 mya


160 mya

First mammal

240 mya

Mesozoic era begins

320 mya

Pangaea forms

260 mya


300 mya


330 mya


370 mya


400 mya


450 mya


520 mya


545 mya

Paleozoic era begins

545 mya

Green algae

1 bya


3 bya

Precambrian era begins

4.6 bya

Figure 1. Events on the geological timeline

* Note (mya= million years ago, bya= billion years ago). These dates are approximations and will vary depending on sources consulted.


2) Divide students into four groups and give each group a set of the prepared cards.

3) Have groups discuss the events and based on their prior knowledge and understanding, arrange the events or organisms from oldest to youngest (or most recent).

4) The hook and look fastener line is identified as a timeline of Earth’s history. Student groups should place their events in order of occurrence on the line.

5) Discuss the arrangement of different student groups and have them give reasons for their answers.

6) The correct order of events and times is provided on an overhead transparency or a prepared handout.

7) Ask student groups to convert the event times to distances for timeline placement.

Remind them that each clothesline is 4.6 meters long.

8) Student groups use meter sticks and metric measuring tapes to place their events to scale on the clothesline.

9) Facilitate discussion of each group’s timeline with regard to event development, spacing and the relative length of each era.



The article and lesson plan written by Deb Hemler and Tom Repine:

Hemler, D. and Repine, T.  2002. Reconstructing the geologic timeline. The Science Teacher  69 (4): 32 –35.


The History of Life web page has links to important events in the geological timeline.


This personal website has an illustrated time line with information and good illustrations of organisms that existed throughout earth’s history.


This New York Times article on the DNA typing of Galapagos finches shows that they were different species -


Galapagos tortoises, different shell shapes and necks depending on vegetation on island -

Stone, Richard. The cold zone. Discover, February, 2000, pp. 58-65.
Follow an expedition of scientists as they look for the frozen remains of mammoths in the Taimyr Peninsula of Siberia. Over 1,000 mammoth specimens have been gathered here, including the famous Jarkov mammoth, which was raised from the permafrost in October of 1999. Scientists are hoping to find DNA evidence that will help explain the extinction of the mammoths, and perhaps lead to resurrecting them through cloning!


Interdisciplinary Connections:


Mathematics – Have students create an accurate scale for a timeline using paper tape or a clothesline (For example, 1 cm = 10,000 years).

Fine Arts- Examine how natural history drawings allow us to better understand different species of birds and animals. How do these drawings affect the preservation of these species?

Geography- On a map, trace Darwin’s voyage of the Beagle. For each route, indicate the dates of sail and the species researched on the voyage.